Low clinker systems - Towards a rational use of SCMs for optimal performance
低熟料系统 - 朝着合理使用矿物掺合料以实现最佳性能的方向

Mohsen Ben Haha $^{a,^{*}}$ , Pipat Termkhajornkit $^{b}$ , Alexandre Ouzia $^{a}$ , Siva Uppalapati $^{b}$ , Bruno Huet $^{b}$
莫赫森·本·哈哈 $^{a,^{*}}$ , 皮帕特·特姆卡霍恩基特 $^{b}$ , 亚历山大·乌齐亚 $^{a}$ , 西瓦·乌帕拉帕提 $^{b}$ , 布鲁诺·于埃 $^{b}$ $^{a}$ Heidelberg Materials, Heidelberg Technology Center, Leimen, Germany
海德堡材料，海德堡技术中心，莱门，德国 $^{b}$ Holcim, Holcim Innovation Center, Lyon, France
$^{b}$ 霍尔西姆，霍尔西姆创新中心，法国里昂

A R T I C L E IN F O
文章信息

Keywords: 关键词：

Portland clinker 波特兰熟料
SCM 供应链管理
performance 表现

{CO}_{2}

footprint

{CO}_{2}

足迹
process 过程

Abstract 摘要

Progress in understanding the use of SCMs in blended Portland cement and related effects is reviewed. An optimized use of cement components will avoid wasting unreacted particles that do not contribute to the mechanical and durability performances. The reactivity of cement components increases with fineness and by controlled production processes. Clinker may become a minor component in the cementitious mix due to the optimized particle packing of blended cements. An optimized mineralogy of the clinker coupled to the addition of activators can help to further reduce its use in composite cements while maintaining concrete performance. Other cement constituents introduce different filler and chemical effects to the overall reaction and contributes differently to the performance. Filler and chemical effects influence the hydrates assemblage and in particular C-S-H formation, morphology, and chemical composition. The cement and concrete properties at different ages are tightly linked to these properties. Future approaches could be more technical than simply grinding and blending, allowing a better use of each cement component to achieve a lower ${CO}_{2}$ intensity.
对掺合料在混合波特兰水泥中的使用及相关影响的理解进展进行了回顾。优化水泥成分的使用将避免浪费不反应的颗粒，这些颗粒对机械性能和耐久性没有贡献。水泥成分的反应性随着细度的增加和受控生产过程而提高。由于混合水泥的颗粒优化堆积，熟料可能成为水泥混合物中的次要成分。优化熟料的矿物组成结合激活剂的添加可以进一步减少其在复合水泥中的使用，同时保持混凝土性能。其他水泥成分引入不同的填充和化学效应，对整体反应产生不同的贡献。填充和化学效应影响水合物的组合，特别是 C-S-H 的形成、形态和化学组成。不同龄期的水泥和混凝土性能与这些特性紧密相关。未来的方法可能比单纯的研磨和混合更具技术性，从而更好地利用每种水泥成分，以实现更低的 ${CO}_{2}$ 强度。

1. Introduction 1. 引言

Under the Paris agreement negotiated during COP 21 in 2015, 195 countries acknowledged the need to limit the global temperature increase of

{1.5}^{\circ} C

by controlling their greenhouse gas emissions [1]. Carbon dioxide

({CO}_{2})

and methane

({CH}_{4})

are the two main anthropogenic greenhouse gases [2].
根据 2015 年在巴黎气候大会（COP 21）达成的协议，195 个国家承认需要通过控制温室气体排放来限制全球温度上升

{1.5}^{\circ} C

[1]。二氧化碳

({CO}_{2})

和甲烷

({CH}_{4})

是两种主要的人为温室气体[2]。

Production of clinker for cement is a heavy industrial process that is associated with significant

{CO}_{2}

emissions: about 800 kilogram of carbon dioxide per ton of cement (noted

[{kgCO}_{2} / t_{cement}]

) is the reference value for

{CO}_{2}

emissions from cement production in the early 90’s [3]. About two thirds from these emissions are related to the decarbonation of limestone for clinker and one third is related to the fuel consumption of the kiln. The global

{CO}_{2}

emissions from decarbonation of limestone for clinker represents

3 %

of the global

{CO}_{2}

emissions [2].
水泥熟料的生产是一个重工业过程，伴随着显著的

{CO}_{2}

排放：每吨水泥约 800 千克二氧化碳（参考值

[{kgCO}_{2} / t_{cement}]

）是 90 年代早期水泥生产

{CO}_{2}

排放的参考值[3]。其中约三分之二的排放与熟料石灰石的脱碳有关，三分之一与窑的燃料消耗有关。全球因熟料石灰石脱碳而产生的

{CO}_{2}

排放占全球

{CO}_{2}

排放的

3 %

[2]。

Before the Paris agreement in 2015, several authors highlighted different strategies to reduce the carbon footprint of cements. As early as 2004, Gartner [4] showed the difficulties of alkali activated materials and was supporting belite ye’elimite ferrite (BYF) cement. In 2010, John et al. [5] proposed a

{CO}_{2}

index at the concrete level

({kgCO}_{2} / m 3

concrete / MPa) to highlight the efficient use of clinker and binder at the
在 2015 年巴黎协议之前，几位作者强调了减少水泥碳足迹的不同策略。早在 2004 年，Gartner [4] 就展示了碱激活材料的困难，并支持贝利特耶利米特铁酸盐（BYF）水泥。2010 年，John 等人 [5] 提出了一个

{CO}_{2}

指数，在混凝土水平

({kgCO}_{2} / m 3

混凝土/MPa）以突出熟料和粘合剂的有效使用。
concrete level. In 2014 Scrivener [6], based on the experimental work of Antoni [7,8], showed that a promising route was ternary cements composed of clinker, calcined clay and limestone.
混凝土水平。2014 年，Scrivener [6] 基于 Antoni [7,8] 的实验工作，表明一种有前景的途径是由熟料、煅烧粘土和石灰石组成的三元水泥。

The consensus of a group of experts initiated by the United Nations Environment Program Sustainable Building and Climate Initiative lead by Scrivener [9] showed that optimizing Portland cement to make it compatible with the objectives of the Paris agreement is the main strategy for the next decade to lower concrete

{CO}_{2}

emissions. The main arguments for OPC are the availability of raw materials, the maturity of the current technologies, and the adoption by current market. Nevertheless, they mention two further levers to reduce the

{CO}_{2}

footprint of concrete: to increase the level of clinker substitution in cement and to decrease the cement content in mortar and concretes.
由联合国环境规划署可持续建筑与气候倡议发起的一组专家达成的共识显示，优化波特兰水泥以使其与《巴黎协定》的目标相兼容是未来十年降低混凝土

{CO}_{2}

排放的主要策略。支持波特兰水泥的主要论据包括原材料的可获得性、当前技术的成熟度以及市场的接受度。然而，他们还提到两个进一步的杠杆来减少混凝土的

{CO}_{2}

足迹：提高水泥中熟料替代的比例以及减少砂浆和混凝土中的水泥含量。

Since the entry into force of the Paris Agreement and Scrivener et al’s paper, public institutions, professional associations, and main industrial players have issued their own roadmaps to reduce the

{CO}_{2}

emissions of the cement industry. The International Energy Agency (IEA) in 2018 [10], the European Cement Association (Cembureau) in 2020 [3], the Global Cement and Concrete association (GCCA) (see Fig. 1) in 2022 [11], Heidelberg Materials in its 2021 sustainability report [12] and Holcim (LafargeHolcim at the time of publication) in its 2019 [13] and
自《巴黎协定》生效以来，以及 Scrivener 等人的论文发布后，公共机构、专业协会和主要行业参与者已发布各自的路线图，以减少水泥行业的

{CO}_{2}

排放。国际能源署（IEA）在 2018 年[10]，欧洲水泥协会（Cembureau）在 2020 年[3]，全球水泥和混凝土协会（GCCA）（见图 1）在 2022 年[11]，海德堡材料在其 2021 年可持续发展报告中[12]，以及 Holcim（在发布时为 LafargeHolcim）在其 2019 年[13]中。

2020 [14] integrated annual reports have issued their own roadmaps. In short, these roadmaps rely on five pillars, the so called 5 "C"s for Clinker, Cement, Concrete, Construction and Carbonation as proposed by the Cembureau:
2020 年[14]综合年度报告已发布各自的路线图。简而言之，这些路线图依赖于五个支柱，即 Cembureau 提出的五个“C”：熟料、水泥、混凝土、建筑和碳化。

Clinker: to reduce ${CO}_{2}$ emissions at the clinker level by using both alternative fuels and alternative raw materials with the emissions of ${CO}_{2}$ at the kiln per ton of clinker $({kgCO}_{2} / t_{clinker})$ as performance criterion.
熟料：通过使用替代燃料和替代原材料，在熟料水平上减少 ${CO}_{2}$ 排放，以 $({kgCO}_{2} / t_{clinker})$ 每吨熟料的窑排放 ${CO}_{2}$ 作为绩效标准。
Cement: to reduce the clinker content in cement by adding supplementary cementitious materials (SCM) with the aggregated ${CO}_{2}$ emissions of constituents per ton of cement $({kgCO}_{2} / t_{cement})$ as performance criterion.
水泥：通过添加补充水泥材料（SCM）来减少水泥中的熟料含量，以每吨水泥的成分总排放量 ${CO}_{2}$ 作为性能标准 $({kgCO}_{2} / t_{cement})$ 。
Concrete: to reduce the cement content in concrete for the same structural performance with the compressive strength by the absolute ${CO}_{2}$ content per unit volume of concrete ( $MPa / ({kgCO}_{2} /$ $m^{3}$ concrete) as a performance criterion.
混凝土：在相同的结构性能下，通过每立方米混凝土的绝对 ${CO}_{2}$ 含量（ $MPa / ({kgCO}_{2} /$ $m^{3}$ 混凝土）作为性能标准，减少混凝土中的水泥含量以达到相同的抗压强度。
Construction: to reduce the concrete content in the structure by optimizing the design and performance of concrete with ${CO}_{2}$ aggregated emissions per unit surface of building $({kgCO}_{2} / m^{2})$ during the building stage but also during the use phase of the building to lower energy demand by optimizing thermal mass and insulation.
建设：通过优化混凝土的设计和性能，在建筑阶段以及建筑使用阶段减少结构中混凝土的含量，降低每单位建筑表面的 ${CO}_{2}$ 聚合物排放 $({kgCO}_{2} / m^{2})$ ，同时通过优化热质量和绝缘来降低能耗。
Carbonation: to account for cement natural carbonation in mortar and concrete products $({kgCO}_{2})$
碳化：考虑砂浆和混凝土产品中水泥的自然碳化 $({kgCO}_{2})$

Therefore, the key elements of sustainable cement production are material efficiency and circular economy supported by technology. For the first three levers, the use of anthropogenic feedstock

[15, 16]

is seen as an interesting alternative which has a minimum impact on the economics of cement production [17] but could influence the

{CO}_{2}

footprint of the cement based products. Note that depending on the country, SCM are added either at the cement level or at the concrete level, modifying
因此，可持续水泥生产的关键要素是材料效率和技术支持的循环经济。对于前三个杠杆，使用人造原料

[15, 16]

被视为一种有趣的替代方案，对水泥生产的经济影响最小[17]，但可能会影响水泥基产品的

{CO}_{2}

足迹。请注意，根据不同国家，SCM 要么在水泥层面添加，要么在混凝土层面添加，从而进行修改。
either the second or the third pillars.
第二或第三支柱。
In recent years, studies have focused on three aspects: the cement constituents (1) and their manufacturing process (2) to meet the expected performance of cement in building products (3). This article focuses on reviewing the first two pillars (Clinker and Cement). but some aspects regarding Concrete (

3^{rd}

) and Carbonation (

5^{th}

pillar) will also be discussed. This paper reviews significant literature published mainly since 2016 on: 1) cement constituents (Section 2), on cement processes (Section 3) and on cement performance (Section 4).
近年来，研究主要集中在三个方面：水泥成分（1）及其生产过程（2），以满足建筑产品中水泥的预期性能（3）。本文重点回顾前两个支柱（熟料和水泥），但也会讨论一些关于混凝土（

3^{rd}

）和碳化（

5^{th}

支柱）的内容。本文回顾了自 2016 年以来发表的主要文献，内容包括：1）水泥成分（第 2 节）、水泥工艺（第 3 节）和水泥性能（第 4 节）。

The Concrete, Construction and Carbonation pillars will be briefly mentioned in the performance Section 5. In particular, carbonation from life cycle analysis (LCA) or durability point of views is exactly the same physical and chemical process; only the performance criterion differs: bound

{CO}_{2}

per volume of concrete or per functional unit for the LCA or carbonation depth over time for ensuring durability of reinforced concrete [18].
混凝土、施工和碳化这三个支柱将在第 5 节的性能部分中简要提及。特别是，从生命周期分析（LCA）或耐久性角度来看，碳化是完全相同的物理和化学过程；只有性能标准不同：每立方米混凝土或每个功能单位的结合

{CO}_{2}

，或者为了确保钢筋混凝土的耐久性而随时间变化的碳化深度[18]。

In terms of clinker and cement composition (Section 2), recent studies have focused on extending the range of composition of cements and extending the nature of SCMs considered in standards. This paper reviews binary and ternary blends composition based on standard constituents like Limestone filler, ground granulated blast furnace slag (GGBS), fly-ash (FA), calcined clay limestone binary and ternary blends.
在熟料和水泥成分方面（第 2 节），最近的研究集中在扩展水泥成分的范围和扩展标准中考虑的矿物掺合料的性质。本文回顾了基于标准成分的二元和三元混合物的组成，如石灰石填料、磨细的高炉矿渣（GGBS）、粉煤灰（FA）、煅烧粘土石灰石的二元和三元混合物。

Then, in terms of processing (Section 3), the clinker quality is key to keep early strength high, as substitution by SCMs may lead to low early age strength. Therefore, recent literature on optimizing fineness on clinker through grinding and grinding aids is reviewed. Also, the addition of clinker mineralizer to optimize the phase assemblage and lower the clinkering temperature is documented. Finally, the calcination of SCMs like clay is a key process to achieve late strength in limestone calcined clay cement to convert kaolin into reactive metakaolin.
然后，在加工方面（第 3 节），熟料质量是保持早期强度高的关键，因为使用矿物掺合料可能导致早期强度低。因此，最近关于通过磨细和磨助剂优化熟料细度的文献进行了回顾。此外，添加熟料矿化剂以优化相组合并降低熟化温度的做法也得到了记录。最后，像粘土这样的矿物掺合料的煅烧是实现石灰石煅烧粘土水泥晚期强度的关键过程，以将高岭土转化为反应性偏高岭土。

Finally, in terms of performance (Section 4), several key properties of cement need to be ensured such that they comply with standards or
最后，在性能方面（第 4 节），需要确保水泥的几个关键特性符合标准或

Fig. 1. GCCA roadmap to reach net zero in 2050 [11].
图 1. GCCA 到 2050 年实现净零排放的路线图 [11]。
regulations for concrete, mortar or other products valid in the place of use. For ready mix concrete applications, the early compressive and flexural strength (at 2 days), and the late strength ( 28 d ) are key properties of cement. For precast applications, specific strength threshold should be achieved even at 12 to 16 hours. To optimize the rheology and sulfate content of cement is also a key to ensure a good placement of concrete. Beyond strength testing, to characterize SCM reactivity for fast screening of SCM and use both thermodynamic calculations and measurements to confirm volume efficiency of the hydrates by measuring or estimating them through thermodynamic calculations are also important. Furthermore, there is a need for optimizing the performance of cement at the product level by modifying clinker content and performance, water to cement ratio and optimizing therefore the compressive strength over the embodied

{CO}_{2}

. Finally, it is expected from cement in product to maintain performance over time, therefore the link between low

{CO}_{2}

cement and corrosion initiated by

{CO}_{2}

or chloride ingress is reviewed.
在使用地点有效的混凝土、砂浆或其他产品的规定。对于预拌混凝土应用，早期抗压和抗弯强度（在 2 天时）以及后期强度（28 天）是水泥的关键特性。对于预制应用，特定的强度阈值应在 12 到 16 小时内达到。优化水泥的流变性和硫酸盐含量也是确保混凝土良好浇筑的关键。除了强度测试外，快速筛选矿物掺合料（SCM）以表征其反应性，并使用热力学计算和测量来确认水合物的体积效率，通过测量或估算它们也是重要的。此外，还需要通过修改熟料含量和性能、水泥与水的比例来优化水泥在产品层面的性能，从而优化抗压强度。最后，期望水泥在产品中能够保持性能，因此回顾了低

{CO}_{2}

水泥与

{CO}_{2}

引发的腐蚀或氯离子侵入之间的联系。

2. Low CO2 cement compositions
2. 低二氧化碳水泥配方

2.1. Carbonates containing cements
2.1. 含水泥的碳酸盐

Limestone is widely available and has long been used in cement. Its effects on cement hydration and mechanical properties have been extensively studied [19-24]. By substituting Portland cement with some limestone, the effective water-to-cement ratio is increased (dilution effect), allowing more space for clinker particles to hydrate.
石灰石广泛可得，长期以来一直用于水泥。它对水泥水化和机械性能的影响已被广泛研究[19-24]。通过用一些石灰石替代波特兰水泥，有效的水灰比得以提高（稀释效应），为熟料颗粒水化提供了更多空间。

Limestone can also improve cement hydration by increasing the heterogeneity of C-S-H growth. Microscopic observations by Berodier and Scrivener [25] showed that limestone increased C-S-H growth more effectively than quartz filler. Using zeta potential measurement, Ouyang et al. [26] pointed out that a strong adsorption of calcium ions from C-SH onto calcite particles is occurring, which was explained by the high affinity for

{Ca}^{2 +}

ions on limestone surface. Because of its similar isoelectric point, micronized quartz had a similar surface charge to C-S-H, which explains why

{Ca}^{+ 2}

ions are not chemically adsorbed on its surface. In addition to providing surface for C-S-H precipitation, limestone reacts with aluminate to form stable hemi- and monocarboaluminate phases [19,27,28] in cementitious systems, thus stabilizing the ettringite and resulting in a higher total volume of hydrates than in non-limestone systems.
石灰石还可以通过增加 C-S-H 生长的异质性来改善水泥水化。Berodier 和 Scrivener 的显微观察显示，石灰石比石英填料更有效地促进 C-S-H 的生长。Ouyang 等人通过ζ电位测量指出，C-S-H 上的钙离子强烈吸附到方解石颗粒上，这可以通过石灰石表面对

{Ca}^{2 +}

离子的高亲和力来解释。由于其相似的等电点，微米级石英与 C-S-H 具有相似的表面电荷，这解释了为什么

{Ca}^{+ 2}

离子不会在其表面上化学吸附。除了为 C-S-H 沉淀提供表面外，石灰石还与铝酸盐反应，在水泥体系中形成稳定的半碳铝酸盐和单碳铝酸盐相，从而稳定膨胀石，并导致比非石灰石体系更高的水合物总体积。

A better understanding of how limestone and cement hydration interact could lead to new strategies for optimizing sustainable mixture designs.
对石灰石和水泥水化相互作用的更好理解可能会导致优化可持续混合设计的新策略。

The surface/fineness of the limestone plays a major role in the acceleration effect at a given replacement level [29]. The heat data of the cement studied by Briki et al [20] when using fine and coarse limestone clearly shows a linear relationship between heat released and available surface for hydration as shown in the Fig. 2. The highest heat released after one day of hydration was attributed to fine limestone, which has the highest surface area for C-S-H nucleation. Despite having a similar available surface area, quartz used in the same study [20] is less favorable for C-S-H nucleation, as previously discussed. Furthermore, the lower the amount of fine limestone in blended cement, the less heat is released.
石灰石的表面/细度在给定替代水平下对加速效应起着重要作用[29]。Briki 等人[20]研究的水泥热量数据表明，使用细石灰石和粗石灰石时，释放的热量与水化可用表面之间存在明显的线性关系，如图 2 所示。水化一天后释放的最高热量归因于细石灰石，因为它具有最高的 C-S-H 成核表面积。尽管在同一研究中使用的石英具有相似的可用表面积，但如前所述，它对 C-S-H 成核的促进作用较差。此外，掺合水泥中细石灰石的含量越低，释放的热量就越少。

It is important to note this beneficial effect of fine limestone, when an increase in the degree of cement hydration particularly at early ages may be able to partially offset the detrimental effects of reduced cement content on hardened properties [20]. From an industrial standpoint, these results suggest that the 10-15% fine limestone could be co-ground with clinker, while the coarse fraction could simply be crushed and added later.
重要的是要注意细石灰石的这种有益效果，当水泥水化程度在早期阶段的增加能够部分抵消水泥含量减少对硬化性能的不利影响时[20]。从工业的角度来看，这些结果表明，10-15%的细石灰石可以与熟料共同研磨，而粗颗粒则可以简单地破碎后再添加。

A recent study carried out by Zajac and al [21] on OPC limestone cements using up to 50% limestone replacement and varying water/ cement and limestone/cement ratios showed that the mechanical properties of the main hydrated phase, the C-S-H, are governed by the
最近，Zajac 等人[21]对使用高达 50%石灰石替代的 OPC 石灰石水泥进行的研究显示，主要水合相 C-S-H 的机械性能受水/水泥和石灰石/水泥比的影响

Fig. 2. Linear correlation between heat evolved and surface available for hydration (L: limestone, Q: Quartz, F:fine, C: Coarse). To blend PC with 20% of limestone may either have no effect on the hydration (coarse limestone case) or increase its heat of hydration by 30% (fine enough limestone) after 24hours. Therefore, the surface rather than the mass replacement matters. N.B. by cement is meant Portland Cement,

H

denotes the heat of hydration as measured by

20^{\circ} C

isothermal calorimetry at 24 hours,

S_{Filler}

and

S_{Cement}

denote the BET surface areas of the SCMs (limestone or quartz) and Portland cement respectively.
图 2. 释放的热量与水合可用表面之间的线性相关性（L：石灰石，Q：石英，F：细，C：粗）。将普通水泥与 20%的石灰石混合可能对水合没有影响（粗石灰石情况），或者在 24 小时后增加其水合热量 30%（足够细的石灰石）。因此，表面而非质量替代更为重要。注意，水泥指的是波特兰水泥，

H

表示在 24 小时内通过

20^{\circ} C

等温量热法测量的水合热量，

S_{Filler}

和

S_{Cement}

分别表示 SCM（石灰石或石英）和波特兰水泥的 BET 表面积。
available space. It was shown that the space available modifies the C-S-H microstructure, which in turn is reflected in the pore volume and porosity distribution. In high-porosity environments, a

C - S - H

with higher amount of gel pores forms and efficiently fills the porosity. Contrarily, in low-porosity environments, a coarse microstructure is developed. Additionally, the available space has an impact on the clinker reaction and chemical composition of the C-S-H. It can alone be responsible for part of the microstructure modifications ascribed in other studies to the pozzolanic and semi-hydraulic reactions such as lower

Ca / Si

ratio of

C - S - H

and different Portlandite content at comparable clinker reaction. A higher

Ca / Si

ratio is observed at lower W/B ratios due to the increase of the supersaturation needed to precipitate Portlandite at these ratios.
可用空间。研究表明，可用空间会改变 C-S-H 微观结构，这反过来又反映在孔体积和孔隙率分布上。在高孔隙率环境中，形成了具有较多胶体孔的

C - S - H

，有效填充了孔隙率。相反，在低孔隙率环境中，发展出粗糙的微观结构。此外，可用空间对熟料反应和 C-S-H 的化学成分有影响。它可能单独负责部分微观结构的变化，而在其他研究中，这些变化被归因于火山灰和半水硬反应，例如在可比熟料反应下，较低的

Ca / Si

与

C - S - H

比率和不同的波特兰石含量。在较低的水胶比下，由于需要增加过饱和度以在这些比率下沉淀波特兰石，因此观察到较高的

Ca / Si

比率。

Using dolomite instead of limestone leads to different observations [30-34]. Mechanical performances observed between limestone and dolomite Portland blends are comparable. However, as dolomite ( CaMg

{({CO}_{3})}_{2})

dissolves in the composite systems, part of the alumina is bound with dissolving Mg to form hydrotalcite. The SEM microstructure observations show rims of hydrotalcite rich C-S-H surrounding the dolomite particles. The microstructure shows typically a two-tone appearance and the layer formed later (inner) is darker than the layer formed earlier. The difference is attributed to different hydrates (mixture of all hydrates and almost neat hydrotalcite). The relative amount of available sulfate to alumina increases, thus resulting in the stabilization of ettringite. The total volume of hydrates is increased by the ettringite stabilization besides hydrotalcite formation. Indeed, these hydrates increase the molar volume of the solids. These mechanisms improve the paste’s space filling properties while decreasing its porosity and permeability [30-32]. Ettringite is additionally thanks to the higher S/Al ratio of the pore solution more stable at higher temperatures

(40^{\circ} C

and above) in the systems containing Dolomite than in the systems containing limestone. This leads to higher strengths at higher temperatures of dolomite cement in comparison to the limestone cements

[30, 35]

.
使用白云石代替石灰石会导致不同的观察结果[30-34]。观察到的石灰石和白云石波特兰混合物的机械性能相当。然而，随着白云石（CaMg

{({CO}_{3})}_{2})

）在复合体系中的溶解，部分铝土矿与溶解的镁结合形成水滑石。扫描电子显微镜（SEM）微观结构观察显示，富含水滑石的 C-S-H 环绕在白云石颗粒周围。微观结构通常呈现出两种颜色的外观，后形成的层（内层）比早期形成的层颜色更深。这种差异归因于不同的水合物（所有水合物的混合物和几乎纯净的水滑石）。可用的硫酸盐与铝土矿的相对含量增加，从而导致铝钙石的稳定化。除了水滑石的形成外，铝钙石的稳定化还增加了水合物的总体积。实际上，这些水合物增加了固体的摩尔体积。这些机制改善了浆料的填充性能，同时降低了其孔隙率和渗透性[30-32]。艾特林石由于孔隙溶液中较高的硫/铝比，在含有白云石的系统中比在含有石灰石的系统中在较高温度下更稳定

(40^{\circ} C

。这导致白云石水泥在较高温度下的强度高于石灰石水泥

[30, 35]

。

2.2. Slag limestone cements
2.2. 硅酸盐石灰石水泥

Because of the limited availability of slags in some geographic
由于某些地区矿渣的供应有限
regions and for the purpose of its optimized use, finely ground limestone as a slag replacement component is becoming popular in cement and concrete development [36-42]. This section provides a succinct review of the recent advances in understanding the microstructural properties of slag-limestone cements. Early age hydration, hydrates assemblages and composition, and pore solution are affected by these additions.
为了优化使用，细磨石灰石作为矿渣替代成分在水泥和混凝土开发中变得越来越受欢迎[36-42]。本节简要回顾了对矿渣-石灰石水泥微观结构特性的最新研究进展。早期水化、水合物组合及成分以及孔溶液都受到这些添加剂的影响。

Recent studies on limestone slag cement indicate that limestone powder reacts to a higher extent than observed limestone-Portland systems and its presence influences the overall reaction kinetics of the systems [38,40,43-47]. Higher calcite consumption occurs in slaglimestone systems, however, this is minor at early age [43,45]. This reaction is continuing steadily through the testing periods reported. When using limestone contents above 5%, the ternary slag-limestone blends often have residual calcite after 1 year. However, Amankwah et al

[45, 46]

showed recently that up to

30 %

of the added calcite was consumed after 180 d (for 10 and 20% level of additions).
最近对石灰石矿渣水泥的研究表明，石灰石粉的反应程度高于观察到的石灰石-波特兰系统，其存在影响了系统的整体反应动力学[38,40,43-47]。在矿渣-石灰石系统中，碳酸钙的消耗量较高，但在早期阶段这一现象较小[43,45]。这一反应在报告的测试期间持续稳定进行。当石灰石含量超过 5%时，三元矿渣-石灰石混合物在 1 年后通常会有残余的碳酸钙。然而，Amankwah 等人

[45, 46]

最近显示，在 180 天后，添加的碳酸钙中有多达

30 %

被消耗（对于 10%和 20%的添加水平）。

A variety of factors influence the reaction kinetics of the different components of slag-limestone ternary blends. The formation of hydrates incl. carboaluminate phases, the filler effect, the availability of space for hydrate growth, and the pore solution concentrations have their impacts on the phase assemblage and the resulting microstructure depending on each stage of hydration
多种因素影响炉渣-石灰石三元混合物中不同组分的反应动力学。水合物的形成，包括碳铝酸盐相、填充效应、水合物生长的空间可用性以及孔隙溶液浓度，都会影响相的组合和最终的微观结构，这取决于水化的每个阶段。

The limestone impact goes beyond

AFt / AFm

stability in the presence of slag. The distribution of alumina between the different hydration products is as well influenced [43-45]. The increased carbonate to aluminate ratio in the ternary blends results in higher carboaluminate contents in comparison to binary OPC-limestone blends, which leads to a stabilization of ettringite. This is as well reflected by the higher sulfate to alumina ratio that lowers alumina concentration in the pore solution [45]. As a result, less aluminum is available to incorporate into C-S-H, shown by the decrease of the

Al / Si

ratio in C-A-S-H in comparison to the systems without limestone [45,48]. The higher carboaluminate amounts and the decrease of alumina concentrations in solution, impacts other alumina-bearing phases. Hydrotalcite-like phases have a higher

Mg / Al

ratio than traditionally observed in the binary slag cements [41,45,48].
石灰石的影响超出了在炉渣存在下的稳定性。不同水合产物之间铝土矿的分布也受到影响。三元混合物中碳酸盐与铝酸盐的比率增加，导致与二元普通硅酸盐水泥-石灰石混合物相比，碳铝酸盐含量更高，从而稳定了艾特林石。这也反映在更高的硫酸盐与铝土矿比率上，降低了孔溶液中的铝土矿浓度。因此，可用于结合到 C-S-H 中的铝减少，表现为与不含石灰石的系统相比，C-A-S-H 中的比率下降。更高的碳铝酸盐含量和溶液中铝土矿浓度的降低，影响了其他含铝土矿的相。水滑石类相的比率高于传统二元炉渣水泥中观察到的比率。

The addition of limestone to slag cements accelerates the alite hydration beyond what is observed by the addition of slag only. The acceleration of the reaction of aluminates is very significant [23,48]. Whilst alite reaction is accelerated in binary slag and the one of belite is retarded, in the limestone-containing cements, the alite is accelerated and the belite hydration is comparable to the ordinary Portland cement systems [43,44,49], implying that limestone compensates for the retarded belite reaction in the presence of slag. The addition of limestone to slag cements accelerates as well the aluminate and ferrite reactions [42,50,51].
向矿渣水泥中添加石灰石加速了铝酸盐水化，超出了仅添加矿渣时的观察结果。铝酸盐反应的加速非常显著[23,48]。虽然在二元矿渣中铝酸盐反应加速，而贝利特反应减缓，但在含石灰石的水泥中，铝酸盐反应加速，贝利特水化与普通波特兰水泥系统相当[43,44,49]，这意味着石灰石弥补了矿渣存在时贝利特反应的减缓。向矿渣水泥中添加石灰石也加速了铝酸盐和铁酸盐反应[42,50,51]。

Slag in limestone composite cements reacts slowly in comparison to clinker. As a result, at early ages and at a given replacement level, this increases the effective

w / c

ratio and the space for hydrate growth. The density of limestone is slightly lower than slag. Consequently, the water available per mass for hydration (i.e., dilution effect) would be similar at the very early stages of the reaction while per volume less water is available in the systems containing limestone.
石灰石复合水泥中的矿渣与熟料相比反应较慢。因此，在早期阶段和给定的替代水平下，这增加了有效

w / c

比率和水合物生长的空间。石灰石的密度略低于矿渣。因此，在反应的最初阶段，每单位质量可用于水合的水（即稀释效应）将是相似的，而在含有石灰石的体系中，每单位体积可用的水较少。

At early age, enough space is available for hydrates growth. The rate of dissolution governs the kinetics of the early age reaction [45,49,51]. Despite the lower water volume in systems containing limestone, the effective water to slag + clinker ratio is higher thanks to limestone additions. The higher availability of water in the systems with limestone could account for the slightly higher slag reaction in the presence of limestone

[45, 49]

. Slag hydration requires the availability of water and space. However, other factors, such as pore solution chemistry, must account for some of the differences in hydration behavior. Knowing that aluminum sorption on silicate surface sites slows dissolution of slag grains, lower aluminum levels thanks to the stabilization of AFt and AFm in the pore solution can promote glass and slag dissolution. Lower aluminum concentrations in the limestone-containing blends [45] would thus promote the slag reaction in these systems in comparison to
在早期阶段，有足够的空间供水合物生长。溶解速率决定了早期反应的动力学[45,49,51]。尽管含有石灰石的系统中水的体积较低，但由于添加了石灰石，有效的水与矿渣+熟料的比率更高。含有石灰石的系统中水的更高可用性可能解释了在石灰石存在下矿渣反应略微增强的原因

[45, 49]

。矿渣水化需要水和空间的可用性。然而，其他因素，如孔隙溶液的化学成分，必须解释水化行为中的一些差异。知道铝在硅酸盐表面位点的吸附会减缓矿渣颗粒的溶解，孔隙溶液中 AFt 和 AFm 的稳定导致铝水平降低，可以促进玻璃和矿渣的溶解。因此，含有石灰石的混合物中较低的铝浓度[45]将促进这些系统中矿渣反应的发生。
systems without limestone.
没有石灰石的系统。

2.3. Pozzolan-Carbonates containing cements
2.3. 含火山灰-碳酸盐的水泥

Pozzolans used traditionally to produce composite cements are specially selected. They can be natural or artificial inorganic materials. Their use should improve the physico-chemical and mechanical properties of the cement or at least not worsen these properties. They can have slightly hydraulic(e.g. Calcareous fly ashes) or only pozzolanic properties [52-56]. Besides fly ashes, most of the pozzolans will lead to a non-appreciable increase of the water demand.
传统上用于生产复合水泥的火山灰是经过特别挑选的。它们可以是天然或人工无机材料。它们的使用应改善水泥的物理化学和机械性能，或者至少不恶化这些性能。它们可以具有轻微的水硬性（例如，石灰质粉煤灰）或仅具有火山灰特性[52-56]。除了粉煤灰，大多数火山灰将导致水需求的增加不明显。

Recently more attention was given to calcined clays [52] and natural pozzolans [54]. Pozzolans or calcined clays are alumino-silicates. Their reaction with water produces CAH besides C-S-H.
最近对煅烧粘土[52]和天然火山灰[54]给予了更多关注。火山灰或煅烧粘土是铝硅酸盐。它们与水反应产生 CAH 和 C-S-H。

This CAH is required for carbonates to react with. Indeed, when coupled to silica in the aluminosilicate (AS) glass phase of fly ash and the distorted aluminosilicate layers in calcined clays, the pozzolanic reactions is more complex and in an unbalanced manner leads to the formation of C-A-S-H, CAH and strätlingite as hydration products in the absence of carbonate source. The reaction of limestone in OPC is limited by insufficient CAH available from the clinker. The combination of limestone and an aluminate-containing pozzolans causes calcium carbonate to react more. This synergistic reaction results in more bound water, reduced porosity, and thus higher strength [52,55-60]. The synergetic effect between alumino-silicate materials and limestone powder is attributed to the impact of

{CaCO}_{3}

on the AFm phases which has been observed for pure OPC [61], OPC-fly ash [62] and calcined clays cement [7]. Because alumino-silicates provide additional aluminates to the system via pozzolanic reaction with calcium hydroxide from cement hydration, the impact of limestone powder is amplified [52,53,63-67]. The increased volume of the hydration phases in the reactions demonstrates the effect. Small amounts of limestone powder promote the formation of hemicarbonate rather than monosulphate, which stabilizes ettringite. Monocarbonate is formed with larger limestone reaction and additions. The difference in specific volume of these phases, as well as the higher amount of hydrate water in ettringite vs. AFm, results in an increase in the total volume of hydration phases. This decreases the porosity and, as a result, an increase in strength is observed. Several studies have demonstrated the validity of the synergetic effect of limestone/alumino-silicate materials for various clinker and SCM types [35,53,62,63,66,67].
这种 CAH 是碳酸盐反应所必需的。实际上，当与飞灰的铝硅酸盐（AS）玻璃相结合以及在煅烧粘土中的扭曲铝硅酸盐层时，火山灰反应变得更加复杂，并且以不平衡的方式导致在没有碳酸盐源的情况下形成 C-A-S-H、CAH 和斯特拉丁石作为水合产物。石灰石在普通硅酸盐水泥（OPC）中的反应受到来自熟料的 CAH 不足的限制。石灰石与含铝酸盐的火山灰的结合使得碳酸钙的反应更加活跃。这种协同反应导致更多的结合水、降低的孔隙率，从而提高强度。铝硅酸盐材料与石灰石粉之间的协同效应归因于对 AFm 相的影响，这在纯 OPC、OPC-飞灰和煅烧粘土水泥中都有观察到。由于铝硅酸盐通过与水泥水合反应中的氢氧化钙进行火山灰反应为系统提供额外的铝酸盐，石灰石粉的影响得到了放大。反应中水合相体积的增加证明了这一影响。少量的石灰石粉促进了半碳酸盐的形成，而不是单硫酸盐，这稳定了艾特林石。随着石灰石反应和添加量的增加，形成了单碳酸盐。这些相的比体积差异，以及艾特林石与 AFm 相比含有更高的水合水量，导致水合相的总体积增加。这降低了孔隙率，因此观察到强度的增加。多项研究已证明石灰石/铝硅酸盐材料对各种熟料和矿物掺合料类型的协同效应的有效性[35,53,62,63,66,67]。

Silicate anions have been shown to interact strongly with the precipitating portlandite. On the one hand, portlandite preferentially precipitates on the calcite surface rather than the quartz [68]. Calcite, on the other hand, was shown to dissolve rapidly until its solubility limit, supplying calcium to the pore solution [69]. As a result, it is possible to hypothesize that the presence of limestone causes fine portlandite precipitation due to portlandite nucleation on the limestone. Filler materials such as quartz do not have this effect, possibly due to the poisoning effect of silica [70]; quartz will dissolve slowly in the cement pore solution at high pH , which may result in an increase in Si concentration near the quartz grains. The delay in formation of stable CH nuclei and crystals in the short induction period between 8 and 10 h of hydration has been attributed to poisoning by the sorption of silica species. At the surface of cement grains Ca rich environment is present. This hypothesis also implies that pozzolans (alumino-silicate) do not serve as a preferential nucleation site for portlandite. The large surface area of natural pozzolana or of calcined clays in the absence of limestone increases the number of nuclei, with a slower crystal growth. the effect of adsorption on the silicate’s surfaces retards the nucleation and growth of CH , and CH nuclei can only grow spontaneously from a solution supersaturated with respect to pure CH .
硅酸盐阴离子已被证明与沉淀的水泥石强烈相互作用。一方面，水泥石更倾向于在方解石表面沉淀，而不是在石英上。另一方面，方解石被证明会迅速溶解，直到其溶解度极限，为孔隙溶液提供钙。因此，可以假设石灰石的存在导致细小水泥石的沉淀，因为水泥石在石灰石上成核。像石英这样的填料材料没有这种效果，可能是由于二氧化硅的中毒效应；石英在高 pH 的水泥孔隙溶液中会缓慢溶解，这可能导致石英颗粒附近的硅浓度增加。在水化的短诱导期（8 到 10 小时）内，稳定的氢氧化钙核和晶体的形成延迟被归因于二氧化硅物种的吸附中毒。在水泥颗粒的表面存在富钙环境。这个假设还暗示火山灰（铝硅酸盐）并不作为水泥石的优先成核位点。天然火山灰或煅烧粘土在缺乏石灰石的情况下，较大的表面积增加了晶核的数量，导致晶体生长速度减慢。硅酸盐表面的吸附效应抑制了氢氧化钙（CH）的成核和生长，而氢氧化钙晶核只能在相对于纯氢氧化钙的过饱和溶液中自发生长。

Calcite’s reactivity causes several changes in the hydration process and the resulting microstructure. This is not limited to the formation of carbonate containing AFm. Portlandite distribution differs, with finer microstructure in carbonate-containing samples. According to literature
方解石的反应性导致水合过程和最终微观结构发生多种变化。这不仅限于含碳酸盐的 AFm 的形成。波特兰石的分布有所不同，含碳酸盐样品的微观结构更细。根据文献
[68], the distribution of silicate among the different hydrates is also affected: in carbonate-containing samples, silicate precipitates primarily as low

Ca / Si

C-S-H. Instead, it is strätlingite and C-S-H with a higher

Ca /

Si ratio in the case of quartz analogue. These differences indicate a different mechanism of pozzolanic reaction and have a significant impact on the evolution of performance.
在含碳酸盐的样品中，硅酸盐主要以低

Ca / Si

C-S-H 形式沉淀。而在石英类似物的情况下，则是以斯特拉廷石和具有更高

Ca /

Si 比率的 C-S-H 形式沉淀。这些差异表明了不同的火山灰反应机制，并对性能的演变产生了显著影响。

It is not necessary to use limestone as a carbonate source because dolomite,

CaMg {({CO}_{3})}_{2}

, will work just as well and may even lead to higher strength through the formation of hydrotalcite in addition to traditional AFm phases [31,32,35,68,71]. Calcined clays appear to be the most reactive among all pozzolans and having large synergistic reaction with limestone, and as well dolomite. Carbonates also have an impact on the development of microstructures. Due to the fast reaction of metakaolin in calcined clays cement systems, dolomite effect seems to be lower than limestone one due its lower rate of dissolution, in comparison to limestone and due to its lower calcite content when used as pure materials [31,32,35]. However, in practice we face more the presence of dolomitic limestone and rarely pure dolomite pits.
不必使用石灰石作为碳酸盐来源，因为白云石

CaMg {({CO}_{3})}_{2}

同样有效，甚至可能通过形成水滑石以及传统的 AFm 相来提高强度[31,32,35,68,71]。煅烧粘土在所有火山灰中似乎是反应性最强的，与石灰石和白云石之间具有较大的协同反应。碳酸盐对微观结构的发展也有影响。由于在煅烧粘土水泥体系中偏高岭土的反应速度较快，白云石的影响似乎低于石灰石，因为其溶解速率较低，并且在作为纯材料使用时其方解石含量较低[31,32,35]。然而，在实践中，我们更常见的是白云石石灰石的存在，而纯白云石矿坑则很少。

Calcined clays have only been used recently and its high reactivity opened the eyes to new microstructural features in these systems. Traditionally, the limestone effect on composite cement performance has been linked to ettringite stabilization. The ettringite content is effectively stable in LC3 samples. However, in calcined clay systems where limestone has been replaced by quartz, only limited ettringite decomposition is observed [68]. The high ettringite content observed is reported to be a consequence of the very dense microstructure at later ages and a lack of calcium to stabilize monosulfate. Another mechanism that could account for the higher strength when using carbonate materials is the difference in microstructure caused by silicate distribution differences. The presence of two thermodynamically incompatible phases, strätlingite and portlandite, at the same time emphasizes the importance of the effect of a very dense matrix and local equilibrium that govern hydration in calcined clay systems.
煅烧粘土最近才被使用，其高反应性揭示了这些系统中新微观结构特征。传统上，石灰石对复合水泥性能的影响与艾特林石的稳定性有关。LC3 样品中的艾特林石含量有效稳定。然而，在石灰石被石英替代的煅烧粘土系统中，仅观察到有限的艾特林石分解[68]。观察到的高艾特林石含量被认为是由于后期非常致密的微观结构以及缺乏钙来稳定单硫酸盐。使用碳酸盐材料时可能导致更高强度的另一个机制是由于硅酸盐分布差异引起的微观结构差异。两种热力学不相容相（斯特拉廷石和波特兰石）同时存在，强调了非常致密的基体和局部平衡对煅烧粘土系统中水化过程的重要影响。

2.4. Particle packing 2.4. 粒子堆积

In addition to the chemical composition of clinker and SCM, particle packing is also improved by optimizing the particle size distribution of solids [72,73]. The space filling of solids in cement pastes, mortars or concrete can be maximized so that the initial porosity can be minimized. Excess water or spacing water can be defined as the difference between the real quantity of water and the minimum water needed to fill all porosity between the solids with maximum packing. This excess of water normalized by the specific area defined the water film thickness [74]. Particle packing is a key lever in addition to chemical admixtures to lower water to cement ratio or to lower cement paste content in concrete.
除了熟料和矿物掺合料的化学成分外，通过优化固体的粒径分布也可以改善颗粒堆积[72,73]。在水泥浆、砂浆或混凝土中，固体的空间填充可以最大化，从而最小化初始孔隙率。多余的水或间隙水可以定义为实际水量与填充所有孔隙所需的最小水量之间的差异，这种填充是在最大堆积情况下进行的。通过特定面积归一化的多余水定义了水膜厚度[74]。颗粒堆积是降低水胶比或降低混凝土中水泥浆含量的关键杠杆，除了化学外加剂之外。

The Compressible Packing Model (CPM), first introduced by De Larrard in 1999, accounts for any particle shapes [72]. Different methods can be used to quantify the water demand of a specific granular skeleton, and to optimize the fresh and hardened properties of cement pastes [75-78]: change of the state from pellets to paste or Vicat needle tests, the advantage of the latter being that it is standardized [79]. As early as 2003, Su et al [80] could apply the CPM model to lower paste content by

15 %

in concrete at constant water to cement ratio and constant performance. In 2008, Damtoft et al. [81] mentioned packing as one of the pillar of low

{CO}_{2}

concrete optimization. In 2010, Daminelli et al quantified how packing is affecting environmental performance of real concrete through two main indices: binder intensity or

{CO}_{2}

intensity

(kg / m^{3} / MPa

) [5]. These latter indices can also be used for embodied energy (

MJ / m^{3} / MPa

) [82]. If packing can reduce the embodied

{CO}_{2}

, this strategy can also help in reducing heat of hydration and temperature rise in concrete without compromising the strength [83]. Moreover, when the water content is low, unhydrated binders can act as reinforcements and give a contribution to strength [84].
可压缩包装模型（CPM）由德·拉拉德于 1999 年首次提出，考虑了任何颗粒形状[72]。可以使用不同的方法来量化特定颗粒骨架的水需求，并优化水泥浆的鲜性和硬化性能[75-78]：从颗粒到浆体的状态变化或维卡针测试，后者的优点在于其标准化[79]。早在 2003 年，苏等人[80]就能够应用 CPM 模型在水泥水比和性能恒定的情况下降低混凝土中的浆体含量

15 %

。在 2008 年，达姆托夫等人[81]提到包装是低

{CO}_{2}

混凝土优化的支柱之一。2010 年，达米内利等人量化了包装如何通过两个主要指标影响实际混凝土的环境性能：粘结剂强度或

{CO}_{2}

强度

(kg / m^{3} / MPa

[5]。这些后者指标也可以用于体现能量（

MJ / m^{3} / MPa

）[82]。如果包装可以减少体现

{CO}_{2}

，那么这一策略也可以帮助降低混凝土的水化热和温度升高，而不影响强度[83]。此外，当水分含量较低时，未水合的粘合剂可以作为增强材料，并对强度产生贡献 [84]。

In 2018 John et al. [85] reviewed the potential of limestone fillers for
在 2018 年，约翰等人[85]回顾了石灰石填料的潜力。
the cement industry and cement based materials, suggesting a reduction of up to

70 %

of clinker content (see Fig. 3). In their review, they show how researchers could reduce the binder intensity, highlighting the experimental results of Proske (see Fig. 3) [86,87] or Müller et al. [88], for which the

{CO}_{2}

intensity could reach

2 {kgCO}_{2} / m^{3} / MPa

for compressive strength of about 40 MPa . (See Fig. 4.)
水泥行业和基于水泥的材料，建议减少高达

70 %

的熟料含量（见图 3）。在他们的综述中，他们展示了研究人员如何减少粘合剂强度，强调了 Proske 的实验结果（见图 3）[86,87]或 Müller 等人的研究[88]，其中

{CO}_{2}

强度可达到

2 {kgCO}_{2} / m^{3} / MPa

，对应的抗压强度约为 40 MPa。（见图 4。）

In recent years, the particle packing was applied at the cement level to optimize the packing of Portland Limestone cements, CEM II/A-L or CEM II/B-L [89,90]. The concept was also applied for ternary cement blend with clinker, limestone and calcined clay [91] or metakaolin [92], i.e. with reactive SCMs. The most recent research is focusing on optimizing the entire solid skeleton of cement and concrete, including reactive SCM using natural pozzolans [93,94], fly-ash [94-97], slag [94,96] and metakaolin [97].
近年来，颗粒堆积被应用于水泥水平，以优化波特兰石灰石水泥的堆积，CEM II/A-L 或 CEM II/B-L [89,90]。该概念也被应用于含有熟料、石灰石和煅烧粘土 [91] 或高岭土 [92] 的三元水泥混合物，即与反应性矿物掺合料（SCMs）一起使用。最新的研究集中在优化水泥和混凝土的整个固体骨架，包括使用天然火山灰的反应性 SCM [93,94]、粉煤灰 [94-97]、矿渣 [94,96] 和高岭土 [97]。

2.5. Accelerators of composite cements
2.5. 复合水泥的加速剂

Minor additions are often used in composite cements to improve some of the properties required by the users; alkali additions can for instance increase early strength since decades.
小量添加剂常用于复合水泥中，以改善用户所需的一些性能；例如，碱性添加剂可以在几十年来提高早期强度。

Two hardening acceleration technologies are currently in use and are based on soluble salts and seeding technology:
目前正在使用两种硬化加速技术，基于可溶盐和播种技术：

Salts: Apart from sodium thiocyanate and nitrate, the most important accelerator salts are calcium-based ones [98-103]. They have the following major disadvantages: sensitivity to cement mineralogy, toxicity, regulatory constraints (particularly for chloride in reinforced concrete), and a negative impact on the long-term strength. The presence of the accelerator immediately after mixing changes the hydration conditions, such as the ion concentrations and pH value of the paste’s pore solution. It affects the reactions of cement clinkers as well as the formation of hydrate phases. The reactions are affected by the concentration of ${Ca}^{2 +}$ ions in the pore solution during the early stages of hydration [49].
盐：除了硫氰酸钠和硝酸盐外，最重要的加速剂盐是基于钙的盐[98-103]。它们有以下主要缺点：对水泥矿物组成的敏感性、毒性、监管限制（特别是对钢筋混凝土中的氯化物）以及对长期强度的负面影响。加速剂在混合后立即存在会改变水化条件，例如浆体孔溶液中的离子浓度和 pH 值。它影响水泥熟料的反应以及水合相的形成。这些反应受到水化早期孔溶液中 ${Ca}^{2 +}$ 离子浓度的影响[49]。

SCMs generally react slower than cement. Increased pH is known to activate them. Alkali salt dry activators, mostly carbonates, are safe to use and will establish a high pH in situ by reacting with calcium hydroxide from cement hydration while also forming calcium carbonate with a high surface area, which is probably more reactive with calcium aluminate hydrates than limestone powder[104]. The disadvantage is that, depending on the total alkali content, alkali carbonates may retard cement setting and/or provide slightly lower long-term strength.
SCM 通常比水泥反应慢。已知增加 pH 值可以激活它们。碱盐干激活剂，主要是碳酸盐，使用安全，并且通过与水泥水化产生的氢氧化钙反应，在原位建立高 pH 值，同时形成具有高表面积的碳酸钙，这可能比石灰石粉与钙铝酸盐水合物反应更活跃[104]。缺点是，根据总碱含量，碱碳酸盐可能会延缓水泥的凝结和/或提供略低的长期强度。

Sodium sulfate is also an effective accelerator for aluminatecontaining pozzolans and slag, involving the formation of NaOH in situ for further acceleration and formation of solid ettringite and/or monosulfate with increased water binding. Recently, the effects of alkali sulfate or calcium chloride separately or in combination with amines technology on the strength of OPC-fly ash and OPC-GGBFS cements were investigated [36,105-108]. The compressive strength of the mortars was clearly increased by the combinations (see Fig. 5). Chemical activation was found to be more efficient than conventional grinding [36]. Chemical activation can increase early strength by

100 %

while maintaining higher late strength [36]. At early age, the accelerators increased the amount of ettringite. They could be a viable solution for increasing the early compressive strength of concrete with high amounts of SCM replacements. Some of the chemical activation techniques requires their use at high temperatures (slow dissolution of salts, etc.), rendering them inapplicable to ready-mix concrete but still applicable to precast concrete.
硫酸钠也是一种有效的加速剂，适用于含铝酸盐的火山灰和矿渣，涉及原位生成氢氧化钠以进一步加速并形成固体水合铝酸钙和/或单硫酸盐，从而增加水结合力。最近，研究了碱性硫酸盐或氯化钙单独或与胺技术结合对普通硅酸盐水泥-粉煤灰和普通硅酸盐水泥-矿渣粉的强度的影响。组合的砂浆抗压强度明显提高（见图 5）。化学活化被发现比传统研磨更有效。化学活化可以在保持较高后期强度的同时增加早期强度。在早期阶段，加速剂增加了水合铝酸钙的数量。它们可能是提高高掺量矿物掺合料混凝土早期抗压强度的可行解决方案。一些化学活化技术需要在高温下使用（盐的缓慢溶解等），使其不适用于预拌混凝土，但仍适用于预制混凝土。

Seeding technology: Nanoparticles accelerate the reaction by providing surfaces for heterogeneous nucleation and possibly pozzolanicity. C-S-H seeds appear to be one of the most efficient candidates because they are ideal nucleation substrates for C-S-H products and have a large specific surface area. C-S-H seeds
播种技术：纳米颗粒通过提供异质成核的表面并可能具有火山灰性来加速反应。C-S-H 种子似乎是最有效的候选者之一，因为它们是 C-S-H 产品的理想成核基底，并且具有较大的比表面积。C-S-H 种子

Fig. 3. Results of performance of low

{CO}_{2}

concrete (figure taken from [85] with permission) in terms of

{CO}_{2}

intensity, binder intensity, compressive Strength and clinker to binder ratio.
图 3. 低

{CO}_{2}

混凝土的性能结果（图源自[85]，已获许可），包括

{CO}_{2}

强度、胶结材料强度、抗压强度和熟料与胶结材料比。

Fig. 4. Evolution of low

{CO}_{2}

cement design including particle packing (figure taken from [86] with permission)
图 4. 低

{CO}_{2}

水泥设计的演变，包括颗粒堆积（图源自[86]，已获许可）

Fig. 5. Amines, combined to plasticizer and small amount of sodium sulfate effect on strength development of composite cements containing C:clinker, S: GGBFS, L: limestone, AH: anhydrite, M:PCE, N$: Alkali sulphate, d: DEIPA, adapted from [36]
图 5. 胺与增塑剂和少量硫酸钠结合对含有 C:熟料，S:矿渣水泥，L:石灰石，AH:无水石膏，M:聚合物改性剂，N$: 碱性硫酸盐，d: DEIPA 的复合水泥强度发展的影响，改编自[36]
[109-111] can be obtained through a variety of methods (precipitation method, pozzolanic/hydraulic method, or sol-gel method), each with its own set of characteristics to control the

Ca / Si

ratio and the particle size of C-S-H seeds. The latter is recognized as a critical factor, whereas the former is still being debated and some clarification would be appreciated. The main disadvantage of C-S-H seeds is the lower efficiency at low temperatures and with less reactive cements, as well as an increased demand for water or superplasticizer. The use of polymers during the synthesis of C-S-H is a very promising solution for controlling particle size via inhibition of agglomeration and Ostwald ripening [112,113]. Despite a significant increase in cost and reaction time, the final C-S-H/polymer composite exhibits improved performance.
[109-111] 可以通过多种方法获得（沉淀法、火山灰/水泥法或溶胶-凝胶法），每种方法都有其特定的特征来控制

Ca / Si

比率和 C-S-H 种子的粒径。后者被认为是一个关键因素，而前者仍在争论中，希望能得到一些澄清。C-S-H 种子的主要缺点是在低温和反应性较低的水泥中效率较低，以及对水或超塑化剂的需求增加。在 C-S-H 合成过程中使用聚合物是控制粒径的一个非常有前景的解决方案，通过抑制聚集和奥斯特瓦尔德熟化 [112,113]。尽管成本和反应时间显著增加，最终的 C-S-H/聚合物复合材料表现出改善的性能。

Acceleration is not lasting over time, which means that the benefits of accelerators may be lost at later ages, even on the first day; an accelerator that could address this issue would undoubtedly be a game changer. Long term properties (e.g., strength, porosity, etc.) are sometimes affected when using salt. An important question that has yet to be answered is whether it is possible to improve early strength without having negative long-term consequences. Hypotheses of less optimal hydrate packing in the microstructure are not supported by experimental evidence. At the same degree of hydration, materials with salt accelerators have higher strengths, but a lower degree of hydration in the long term is observed [2,19-22]. Some new research ideas suggest
加速效果不会随着时间的推移而持续，这意味着加速剂的好处可能在后期失去，甚至在第一天就会出现这种情况；能够解决这个问题的加速剂无疑会改变游戏规则。使用盐时，长期特性（例如强度、孔隙率等）有时会受到影响。一个尚未回答的重要问题是，是否可以在不产生负面长期后果的情况下提高早期强度。关于微观结构中水合物堆积不够优化的假设并没有实验证据支持。在相同的水合程度下，使用盐加速剂的材料具有更高的强度，但长期观察到的水合程度较低[2,19-22]。一些新的研究思路建议
that this is due to alkalis lowering water activity [114]. Early strength requirements result sometimes in excessive performance at later ages. This “needed early but useless long-term strength” observation is becoming a rising issue as environmental concerns rise, and it should be explained and exploited as well.
这归因于碱性物质降低了水分活度[114]。早期强度要求有时会导致后期性能过高。这种“早期需要但长期无用的强度”观察随着环境问题的上升而成为一个日益严重的问题，应该加以解释和利用。

2.6. Other technologies 2.6. 其他技术

Recently, the number of publications on the use of nanomaterials in concrete

[115, 116]

has increased significantly. Graphene and its derivatives (GD) and carbon nanotubes (CNTs) are two nano materials that can sometimes improve the properties of cement and concrete [117-124]. However, results in literature vary from study to study and source to source. This makes it almost impossible to have reproducible results among different laboratories and studies. Additionally, the magnitude of effects varies widely in different studies. Indeed, If the used GD or CNTs are provided by the same supplier and the concrete design is made with the same level of dispersion, the results are repeatable. The main issue may link to the production of GD and CNTs. The characteristics of GD or CNTs from one provider may be different from another provider therefore the results in concrete level observed between the different studies are different.
最近，关于在混凝土中使用纳米材料的出版物数量显著增加。石墨烯及其衍生物（GD）和碳纳米管（CNTs）是两种有时可以改善水泥和混凝土性能的纳米材料。然而，文献中的结果因研究和来源而异。这使得在不同实验室和研究之间几乎不可能获得可重复的结果。此外，不同研究中效果的大小差异很大。实际上，如果使用的 GD 或 CNTs 来自同一供应商，并且混凝土设计采用相同的分散水平，结果是可重复的。主要问题可能与 GD 和 CNTs 的生产有关。来自一个供应商的 GD 或 CNTs 的特性可能与另一个供应商的不同，因此在不同研究中观察到的混凝土水平结果也不同。

Graphene, a 2D-atomic crystal, has a very higher surface area (

2630 m 2 / g

) with an excellent Young’s modulus (

\sim 1 TMPa

) [125-127]. Moreover, graphene derivatives, including graphene oxide (GO), reduced GO (rGO) and functionalized GO (FGO), have similar properties as graphene with additional function. GO has hydrophilic properties and is easier to disperse in an aqueous solution [128]. rGO is close to graphene but has more flaws. In order to disperse graphene and GO in solvents and form covalent bonds with various substrates, they must be functionalized by specific functional groups such as poly amine groups, sulfonate groups and amino groups [129]. These GO are known as FGO.
石墨烯是一种二维原子晶体，具有非常高的比表面积（

2630 m 2 / g

）和优异的杨氏模量（

\sim 1 TMPa

）[125-127]。此外，石墨烯衍生物，包括氧化石墨烯（GO）、还原氧化石墨烯（rGO）和功能化氧化石墨烯（FGO），具有与石墨烯相似的特性，并具备额外的功能。GO 具有亲水性，易于在水溶液中分散[128]。rGO 接近石墨烯，但缺陷更多。为了在溶剂中分散石墨烯和 GO，并与各种基材形成共价键，必须通过特定的功能基团如聚胺基团、磺酸基团和氨基团进行功能化[129]。这些 GO 被称为 FGO。

GD can be added to cement paste or concrete mix to improve the mechanical properties of the resulting material. GD can enhance the compressive and flexural strength of the material and increase its Young’s modulus.
GD 可以添加到水泥浆或混凝土混合物中，以改善所得到材料的机械性能。GD 可以增强材料的抗压强度和抗弯强度，并提高其杨氏模量。

CNTs are cylindrical structures made of carbon atoms arranged in a hexagonal pattern, similar to the way carbon atoms are arranged in graphite or graphene. CNTs have a diameter on the order of nanometers, but they can be very long, with lengths on the order of micrometers to millimeters. -GD and CNTs need to be dispersed before using them in cement and concrete.
CNT 是由碳原子以六角形模式排列而成的圆柱形结构，类似于石墨或石墨烯中碳原子的排列。CNT 的直径在纳米级别，但它们可以非常长，长度在微米到毫米级别。-GD 和 CNT 在用于水泥和混凝土之前需要进行分散。

CNTs can be used as a reinforcing agent in cement and concrete. They have high aspect ratios and exceptional mechanical properties, which make them ideal for reinforcing materials. By adding CNTs to cement and concrete, it is possible to increase their tensile strength and toughness.
CNTs 可以作为水泥和混凝土的增强剂。它们具有高的长宽比和卓越的机械性能，使其成为增强材料的理想选择。通过将 CNTs 添加到水泥和混凝土中，可以提高它们的抗拉强度和韧性。

GD and CNTs can also be used to reduce the carbon footprint of cement and concrete production. By adding these materials to the mix, it is possible to reduce the amount of cement needed, which in turn reduces the amount of

{CO}_{2}

emissions generated during production.
GD 和 CNTs 也可以用于减少水泥和混凝土生产的碳足迹。通过将这些材料添加到混合物中，可以减少所需的水泥量，从而减少生产过程中产生的

{CO}_{2}

排放量。

However, the availability and the costs of GD and CNTs associated with its production, transportation, and handling can make it far less cost-effective compared to traditional methods such as a reduction of water-to-cement ratio. In addition their benefit on properties is mainly seen at low water to cement ratio (below 0.35 ) [130,131]. Graphene and carbon nanotubes are currently considered safe for most applications, but their potential health hazards are still being investigated [132].
然而，石墨烯和碳纳米管的可用性及其生产、运输和处理的成本，使其相比于传统方法（如降低水胶比）变得远不那么具成本效益。此外，它们对性能的益处主要在低水胶比（低于 0.35）时显现[130,131]。目前，石墨烯和碳纳米管被认为在大多数应用中是安全的，但它们潜在的健康危害仍在研究中[132]。

2.7. Standards and specifications
2.7. 标准和规范

Standards in general and cement standards for the building industry in particular are one of key elements for the market deployment of cements ensuring expected technical performance and safety for the final user. With the pressure on reducing

{CO}_{2}

emissions, updates of standards since 2018 in different part of the worlds have extended the possibilities
标准一般而言，特别是建筑行业的水泥标准，是水泥市场推广的关键要素之一，确保最终用户的预期技术性能和安全性。随着减少

{CO}_{2}

排放的压力，自 2018 年以来，世界各地的标准更新扩展了可能性。
to reduce the

{CO}_{2}

footprint of industrial cements without compromising the final performance. We document here the key updates for different parts of the world. We comment here on recent updates of cement standards, but one should keep in mind that concrete products or building standards are also required for the deployment of low

{CO}_{2}

materials and solutions for buildings.
为了在不影响最终性能的情况下减少工业水泥的

{CO}_{2}

足迹。我们在这里记录了不同地区的关键更新。我们在这里评论了水泥标准的最新更新，但应该记住，混凝土产品或建筑标准对于低

{CO}_{2}

材料和建筑解决方案的部署也是必需的。

In the European Union (EU), the Cement standard (EN 197-1:2011 [133]) allows for clinker content (Ck) as low as 65% for CEM II or even lower limits for CEM III (

Ck = 5 %

), for CEM IV (

Ck = 45 %

) and for CEM V (

Ck = 20 %

) based on standards components (blast-furnace slags, silica fume, natural pozzolans, natural calcined pozzolans, fly-ash, limestone and burn shale). Recent complementary standards have been deployed to extend the cement composition and categories. In 2021, the EN 197-5 [134] introduced two extended cements: 1) CEM II/ C-M (minimum

Ck = 50 %

) and CEM VI (minimum

Ck = 35 %

). Both cement types allow for dolomitic limestone In terms of composition, CEM II/C-M allow for mixing up to 3 standard constituents including clinker. For example, the so-called LC3-50/30/15 calcined cements extensively studied in the literature can be commercialized as CEM II/CM. CEM VI cements are ternary cements for which either one of natural pozzolans, siliceous fly ash or limestone is added to clinker and blast furnace slag. In 2023, cement with recycled building materials could be specified according to EN 197-6:2023 [135]: this standard allows for the use of recycled concrete fines (RCF as F constituent) with a minimum clinker content as CEM II/B cements (minimum

Ck = 65 %

).
在欧盟（EU），水泥标准（EN 197-1:2011 [133]）允许 CEM II 的熟料含量（Ck）低至 65%，而 CEM III 的限制甚至更低（

Ck = 5 %

），CEM IV（

Ck = 45 %

）和 CEM V（

Ck = 20 %

）的标准成分（高炉矿渣、硅灰、天然火山灰、天然煅烧火山灰、粉煤灰、石灰石和烧结页岩）也有类似规定。最近，补充标准已被推出，以扩展水泥的组成和类别。2021 年，EN 197-5 [134]引入了两种扩展水泥：1）CEM II/C-M（最低

Ck = 50 %

）和 CEM VI（最低

Ck = 35 %

）。这两种水泥类型允许使用白云石石灰石。在组成方面，CEM II/C-M 允许混合最多 3 种标准成分，包括熟料。例如，文献中广泛研究的所谓 LC3-50/30/15 煅烧水泥可以商业化为 CEM II/CM。CEM VI 水泥是三元水泥，其中添加了天然火山灰、硅质粉煤灰或石灰石中的任意一种与熟料和高炉矿渣混合。在 2023 年，符合 EN 197-6:2023 标准的水泥可以根据回收建筑材料进行规定[135]：该标准允许使用回收混凝土细料（RCF 作为 F 成分），其最小熟料含量为 CEM II/B 水泥（最小

Ck = 65 %

）。

Beyond pure market demand, the adoption of low-

{CO}_{2}

cement is also pushed by local regulations and enabled by product standards. As an example, in France, the regulation RE2020 (as explained in the reference guide [136]) pushes the adoption of low

{CO}_{2}

concrete for buildings by analyzing the

{CO}_{2}

footprint of the building by two main carbon related indicators (Ic) measuring the carbon footprint of the building (with the unit

{kgCO}_{2} / m^{2}

) from energy and materials during the construction phase and the use phase. As of 2028, this index for the construction phase should range between 160 and

260 {kgCO}_{2} / m^{2}

[5]. Also in 2022 the French concrete technical guide FD P18-480:2022 [137] enables the use of low

{CO}_{2}

blended cement in concrete providing a minimum cement content is used and the mechanical and durability performance are verified.
除了纯粹的市场需求，低-

{CO}_{2}

水泥的采用还受到地方法规的推动，并通过产品标准得以实现。例如，在法国，法规 RE2020（如参考指南[136]中所解释）通过分析建筑的

{CO}_{2}

足迹，推动低

{CO}_{2}

混凝土在建筑中的采用，主要通过两个与碳相关的指标（Ic）来衡量建筑的碳足迹（单位为

{kgCO}_{2} / m^{2}

），这些指标涵盖了在建设阶段和使用阶段的能源和材料。到 2028 年，建设阶段的这一指数应在 160 到

260 {kgCO}_{2} / m^{2}

之间[5]。此外，在 2022 年，法国混凝土技术指南 FD P18-480:2022 [137]允许在混凝土中使用低

{CO}_{2}

掺合水泥，前提是使用最低水泥含量，并且机械性能和耐久性性能经过验证。

In Switzerland, the recent focus has been not only on reducing the

{CO}_{2}

footprint of cement but also on replacing cement constituents by Anthropogenic Cement Constituents (ACC) [17] which are taken from anthropogenic material stocks [15]. The Code of Practice (CP) SIA 2049 [138] was put into force in 2014 by the Swiss Society of Engineers and Architects (SIA). According to these documents, both natural and anthropogenic constituents can be added to cement (

min Ck = 20 %

) as long as mechanical and durability performance are met. The application to this guide led the Swiss cement industry gaining experience on replacing limestone filler by Concrete Demolition Waste and natural Gypsum by recycled Plaster board [17]. The Swiss experience has set the path for the adoption at the EU level of EN 197-6 [135].
在瑞士，最近的重点不仅是减少水泥的

{CO}_{2}

足迹，还包括用人造水泥成分（ACC）替代水泥成分，这些成分来自人造材料库存[15]。瑞士工程师和建筑师协会（SIA）于 2014 年实施了《实践规范》（CP）SIA 2049[138]。根据这些文件，只要满足机械和耐久性性能，可以将天然和人造成分添加到水泥中（

min Ck = 20 %

）。这一指南的应用使瑞士水泥行业获得了用混凝土拆除废料替代石灰石填料和用回收石膏板替代天然石膏的经验[17]。瑞士的经验为欧盟层面采纳 EN 197-6[135]铺平了道路。

In North America, ASTM, AASHTO and CSA standards are also being updated to allow higher clinker substitution level or extend the range of constituents. The actual ASTM C618-23 [139] specifies the requirements for fly ash and pozzolans for concrete and will allow the use of harvested and processed fly ash, bottom ash and co-mingled ash as coal ash. This has the potential of using over 1 billion tons of landfilled ash in the USA [140]. Also the requirements for blended cements in ASTM C595 [141] are harmonized with AASHTO M 240 [142]: both standards allow Type IL Portland-limestone cements (up to 15% limestone) and Type IT cements with both limestone and either slag or pozzolans as SCM. In Canada, the CSA A3000 [143] was published in 2018 and a forthcoming version shall be released this year (2023). A new SCM, ground glass, can be used with specifications on the alkali content and potential alkali silica reaction (ASR). The fly-ash specifications were revised in 2021 to include fly ash, bottom ash or co-mingled ash to be processed and used as fly ash. Finally, the same type of fly-ash can now be blended and used
在北美，ASTM、AASHTO 和 CSA 标准也在更新，以允许更高的熟料替代水平或扩展成分范围。实际的 ASTM C618-23 [139] 规定了混凝土用粉煤灰和火山灰的要求，并将允许使用收集和处理的粉煤灰、底灰和混合灰作为煤灰。这有可能在美国使用超过 10 亿吨的填埋灰 [140]。此外，ASTM C595 [141] 中对混合水泥的要求与 AASHTO M 240 [142] 协调一致：这两个标准都允许使用 IL 型波特兰石灰石水泥（最多 15%石灰石）和 IT 型水泥，后者同时含有石灰石和矿渣或火山灰作为补充水泥材料（SCM）。在加拿大，CSA A3000 [143] 于 2018 年发布，预计今年（2023 年）将发布新版本。新的补充水泥材料，磨碎的玻璃，可以根据碱含量和潜在的碱硅酸反应（ASR）进行使用。粉煤灰的规格在 2021 年进行了修订，以包括粉煤灰、底灰或混合灰的处理和使用。最后，现在可以将相同类型的粉煤灰混合使用。
as a single source. 作为单一来源。
In Africa, the substitution of cement with limestone in binary or ternary cement is also a strategy. However, over the African continent a lack of calcium carbonate has pushed the authorities to study the addition of dolomitic limestone to clinker. Early 2023, the Ivory Coast announced the possibility to replace calcareous limestone with dolomitic limestone.
在非洲，水泥中用石灰石替代水泥的二元或三元水泥也是一种策略。然而，在整个非洲大陆，碳酸钙的缺乏促使当局研究将白云石石灰石添加到熟料中。2023 年初，象牙海岸宣布有可能用白云石石灰石替代钙质石灰石。

In China, the standards HJ2519-2012 [144], which specifies the environmental requirements of cement, dates back to 2012. It is the only existing Chinese specification that directly gives the carbon footprint limits for cement in China: the

{CO}_{2}

footprint of cement ranges from 240 to

840 {kg}_{-} {CO}_{2} / t_{2}

cement depending on SCM type and strength performance.
在中国，标准 HJ2519-2012 [144]规定了水泥的环境要求，追溯到 2012 年。它是唯一一个直接给出中国水泥碳足迹限制的现有中国规范：水泥的

{CO}_{2}

碳足迹范围从 240 到

840 {kg}_{-} {CO}_{2} / t_{2}

，具体取决于 SCM 类型和强度性能。

3. Process 3. 过程

3.1. Clinker 3.1. 熟料

To address the challenge of early age strength development of blended cements, clinker doping with minor elements has been attempted. The zinc and magnesium doping experiments on alite proved initially promising. Bazzoni et al [145] showed a minor gain by magnesium doping but a major gain by zinc doping of alite on the main hydration peak: at 24 hours, the degree of hydration was increased by

40 %

. Bazzoni suggested the increased heat was related to the increase of C-S-H needle length, a hypothesis quantitatively corroborated by the needle model of Ouzia [146]. Li replicated similar experiments on mortar and showed that the strength of zinc doped alite mortars doubled at 1 and 3 days [147].
为了解决混合水泥早期强度发展的挑战，尝试对熟料进行微量元素掺杂。锌和镁掺杂的实验在铝酸盐上最初显示出良好的前景。Bazzoni 等人[145]显示，镁掺杂对铝酸盐的主要水化峰有小幅提升，而锌掺杂则有显著提升：在 24 小时内，水化程度增加了

40 %

。Bazzoni 建议，热量的增加与 C-S-H 针状晶体长度的增加有关，这一假设得到了 Ouzia 的针状模型[146]的定量证实。李在砂浆上重复了类似的实验，结果显示锌掺杂的铝酸盐砂浆在 1 天和 3 天时强度翻倍[147]。

Teixeira investigated whether these positive results on alite could pass on systems closer to PC. She synthesized

C_{3} A

and

C_{4} AF

multi-phase clinkers and doped them with zinc oxide. She observed a delay rather than an increase of hydration[148]. The retardation effect of zinc in solution can extend to several days has been known for several decades [149,150] but its mechanisms are disputed. Teixeira showed that in multi-phase clinkers an interstitial amorphous phase contained most of the zinc instead of alite. Upon the reaction with water, this phase releases the zinc in solutions thus delaying the hydration. Strategies like changing the cooling rate or turning to a

C_{4} AF

multi-phase clinker rather than a

C_{3} A

were tried to decrease the amount of the zinc containing amorphous phase[148]. Although the retardation was shortened, and the main hydration peak increased, the delay remained in the order of 6 hours.
泰谢拉研究了这些对铝酸盐的积极结果是否可以传递到更接近 PC 的系统。她合成了

C_{3} A

和

C_{4} AF

多相熟料，并用氧化锌掺杂。她观察到水合的延迟而不是增加[148]。锌在溶液中的延迟效应可以持续几天，这一现象已知数十年[149,150]，但其机制存在争议。泰谢拉显示，在多相熟料中，间隙非晶相含有大部分锌，而不是铝酸盐。在与水反应时，这一相释放锌到溶液中，从而延迟水合。尝试通过改变冷却速率或转向

C_{4} AF

多相熟料而不是

C_{3} A

来减少含锌非晶相的数量[148]。尽管延迟缩短，主要水合峰值增加，但延迟仍保持在 6 小时左右。

A recent study by Krishnan et al [151] on the kinetics of reaction of

β - C_{2} S

showed that

β - C_{2} S

reaction is similar to that of

C_{3} S

with a lower rate. The

C - S - H

formed by hydration of

β - C_{2} S

was found to be morphologically and chemically identical to the C-S-H formed by hydration of

C_{3} S

. The presence of alumino-silicate pozzolans, such as calcined clay, was found to affect the hydration kinetics of

β - C_{2} S

, which has practical implications when producing blended cements with belitic clinkers. In composite cements, clinker phases typically hydrate quickly in the early stages, especially the calcium aluminate

(C_{3} A)

and tricalcium silicate phases

(C_{3} S)

. The hydration of cement components slows down after one to three days of hydration as these most reactive phases become depleted or almost depleted. Particularly, amorphous glasses from SCMs and belite (

C_{2} S

) phases react slowly. Recent research suggests that long-term hydration of belite is slowed in blended cement systems containing reactive alumina [152-154]. Several hypotheses have been proposed to explain why aluminum appears to inhibit the silicate reaction. One theory is that the alumina becomes bound on the silicate surface, preventing further dissolution of silicate phases and mainly belite [155,156]. This has been as we reported when studying blends of calcium aluminate cement with OPC[157]. However, the fast kinetic of dissolution alite in comparison to any SCMs makes this observation inexistant for this mineral in blended cements. The pH of the system appears to be important in this regard as well. The detrimental
最近，Krishnan 等人[151]对

β - C_{2} S

反应动力学的研究表明，

β - C_{2} S

反应与

C_{3} S

的反应相似，但速率较低。通过对

β - C_{2} S

的水合形成的

C - S - H

在形态和化学上与通过水合

C_{3} S

形成的 C-S-H 相同。发现铝硅酸盐火山灰（如煅烧粘土）的存在会影响

β - C_{2} S

的水合动力学，这在生产含有贝利特熟料的混合水泥时具有实际意义。在复合水泥中，熟料相通常在早期阶段迅速水合，特别是钙铝酸盐

(C_{3} A)

和三钙硅酸相

(C_{3} S)

。水泥成分的水合在水合一到三天后减缓，因为这些反应性最强的相变得耗竭或几乎耗竭。特别是，来自 SCM 和贝利特（

C_{2} S

）相的无定形玻璃反应缓慢。最近的研究表明，在含有反应性铝土矿的混合水泥体系中，贝利特的长期水合速度减慢[152-154]。提出了几种假设来解释为什么铝似乎抑制硅酸盐反应。一种理论是铝土矿在硅酸盐表面结合，防止硅酸盐相和主要是贝利特的进一步溶解[155,156]。在我们研究钙铝酸盐水泥与普通波特兰水泥的混合物时，这一点得到了证实[157]。然而，与任何矿物掺合料相比，铝酸盐的快速溶解动力学使得在混合水泥中对这种矿物的观察不存在。系统的 pH 值在这方面似乎也很重要。有害的
effect of Al ions on silicate dissolution appears to be reduced at higher pH values [158]. It has also been proposed that the formation of aluminum hydrates reduces the space available for the growth of C-S-H, resulting in a reduction in silicate hydration overall [159]. Results from Krishnan et al [151] confirmed the inhibition of hydration of belite by alumino-silicate. While

β - C_{2} S

and

β - C_{2} S

-quartz systems showed clear exothermic reactions, when mixed with metakaolin

β - C_{2} S

showed little to no reaction. When reactive alumino-silicates are used in blends, the long-term reduction in hydration of belite in the presence of aluminum can result in lower degree of hydration and the related consequences in strength and durability) of cements with high belite contents.
铝离子对硅酸盐溶解的影响在较高的 pH 值下似乎减弱[158]。也有人提出，铝水合物的形成减少了 C-S-H 生长所需的空间，从而整体上减少了硅酸盐的水合[159]。Krishnan 等人的研究结果[151]证实了铝硅酸盐对贝利特水合的抑制。虽然

β - C_{2} S

和

β - C_{2} S

-石英系统在与高岭土混合时显示出明显的放热反应，但

β - C_{2} S

几乎没有反应。当在混合物中使用反应性铝硅酸盐时，铝的存在会导致贝利特水合的长期减少，从而导致水合程度降低及其对高贝利特含量水泥的强度和耐久性相关的后果。

3.2. Clay calcination 3.2. 粘土煅烧

Considering the shortage of classic SCMs (slag and fly ash), the materials which can radically increase the substitution level of clinker and so lead to extensive reductions in emitted

{CO}_{2}

are calcined clay and natural pozzolans.
考虑到经典 SCM（矿渣和粉煤灰）的短缺，可以显著提高熟料替代水平并导致排放

{CO}_{2}

大幅减少的材料是煅烧粘土和天然火山灰。

When raw clays are heated, three major phenomena related to the alumino-silicate material occur with rising temperature: dehydration, dehydroxylation, and recrystallization. The magnitude and temperature range of dehydration depends on many factors such as nature of the cations in the interlayer region. When kaolinite clays are calcined (heated to temperatures ranging from 650 to

850^{\circ} C

), they transform into highly reactive materials [160-163]. Calcined clays work particularly well in combination with limestone due to their high alumina content, which is the synergy behind the LC

^{3}

(limestone calcined clay cement) technology. Clays with a kaolin content of around

40 %

are sufficient [164], and such clays are abundant worldwide - frequently as waste from other mining operations. Dehydroxylation, releases structural hydroxyls into the surrounding atmosphere over a wide temperature range, with the specific temperature interval determined by the type and abundance of clay minerals present in the raw material. 1:1 clay minerals dehydroxylate at lower temperatures and over a narrower temperature range than 2:1 clay mineral[162]. Overlapping of temperature ranges frequently happen in a complex mineralogical composition. Finally, above

850^{\circ} C

, recrystallization occurs, indicating the conversion of structurally disordered, potentially reactive phases to more stable, high-temperature phases with no pozzolanic reactivity.
当原土加热时，随着温度的升高，与铝硅酸盐材料相关的三种主要现象发生：脱水、脱羟基化和重结晶。脱水的幅度和温度范围取决于许多因素，例如层间区域阳离子的性质。当高岭土粘土被煅烧（加热到 650 到

850^{\circ} C

度的温度范围内）时，它们转变为高度反应性材料[160-163]。煅烧粘土与石灰石结合效果特别好，因为它们的铝土矿含量高，这也是 LC

^{3}

（石灰石煅烧粘土水泥）技术的协同作用。含有约

40 %

的高岭土的粘土是足够的[164]，这种粘土在全球范围内丰富，通常是其他采矿作业的废料。脱羟基化在较宽的温度范围内将结构羟基释放到周围的气氛中，具体的温度区间由原材料中存在的粘土矿物的类型和丰度决定。1:1 粘土矿物在较低的温度下脱羟基化，并且温度范围比 2:1 粘土矿物更窄[162]。在复杂的矿物组成中，温度范围的重叠经常发生。最后，在

850^{\circ} C

以上，发生再结晶，表明结构无序的、潜在反应相转变为更稳定的高温相，且没有火山灰反应性。

The actual dehydroxylation temperature will be determined by several factors, including the fineness of the clay, the pressure of the surrounding atmosphere, specifically the water vapor partial pressure, as well as structural features of the clay mineral and crystallinity [165-167]. The dehydroxylation temperature of the clay rises with increasing

H_{2} O

partial pressure, which varies greatly depending on fuel, for example,

20 %

for natural gas combustion in air and

1 %

for an electric furnace (by volume) (air). Recent research has also shown that co-calcining clays with other minerals (e.g., dolomite, limestone, marl) can result in SCMs with higher pozzolanic activity [168-170]. However, the carbonate content should be considered in the

{CO}_{2}

that may be generated. An increase in

{CO}_{2}

fugacity raises the temperature of carbonate decomposition, which can be useful in some cases to avoid the reaction of subsequent CaO with the alumino-silicate material. Because of clays low thermal conductivity and varying particle size distribution, calcination may be uneven, and some unconverted material may remain if the temperature is not controlled. It is also known that sintering and recrystallization of clay take place at higher temperatures, reducing their reactivity [162]. Although clay calcination can be carried out using many techniques, static, rotary, and flash calcination are the most common.
实际的脱羟温度将由多个因素决定，包括粘土的细度、周围气氛的压力，特别是水蒸气的分压，以及粘土矿物的结构特征和结晶度[165-167]。随着

H_{2} O

分压的增加，粘土的脱羟温度上升，这在很大程度上取决于燃料，例如，

20 %

用于空气中的天然气燃烧，

1 %

用于电炉（按体积）（空气）。最近的研究还表明，与其他矿物（例如白云石、石灰石、泥灰岩）共同煅烧粘土可以产生具有更高火山灰活性的 SCM[168-170]。然而，碳酸盐含量应考虑在可能生成的

{CO}_{2}

中。

{CO}_{2}

逸度的增加提高了碳酸盐分解的温度，这在某些情况下可以避免后续 CaO 与铝硅酸盐材料的反应。由于粘土的低热导率和不同的颗粒大小分布，煅烧可能不均匀，如果温度未得到控制，可能会残留一些未转化的材料。众所周知，粘土的烧结和再结晶在较高温度下发生，从而降低其反应性[162]。虽然粘土的煅烧可以采用多种技术，但静态、旋转和闪蒸煅烧是最常见的。

3.3. Grinding of cement 3.3. 水泥磨粉

Given that the most effective route to reducing

{CO}_{2}

emissions for cement is to maximize the addition of SCMs, several technologies are proposed to enhance the OPC early age reactivity to facilitate the
考虑到减少水泥

{CO}_{2}

排放的最有效途径是最大化添加 SCMs，提出了几种技术来增强 OPC 早期反应性以促进
formulation of cements with desired strength. Possible routes are better grinding strategies to increase clinker reactivity. The simplest way to increase the surface area for C-S-H growth is to grind the cements finer. However, this has the disadvantage of increasing water demand (the amount of water required for a given consistency) as well as the energy required for grinding. However, in multi-component blends, clinker is only one constituent, and water demand can be kept reasonable by grinding and blending strategies that maximize the clinker component in the fine fraction while maintaining a similar overall particle size distribution [171,172]. Separate grinding followed by blending is often the preferable technology for optimizing the relative particle sizes of the various components. Another important factor in achieving good particle size distributions with the least amount of energy is the use of grinding aids [173].
水泥的配方需要达到所需的强度。可能的途径是改善磨矿策略以提高熟料的反应性。增加 C-S-H 生长的表面积最简单的方法是将水泥磨得更细。然而，这会带来增加水需求（为了达到一定稠度所需的水量）以及磨矿所需能量的缺点。然而，在多组分混合物中，熟料只是一个成分，通过磨矿和混合策略可以合理控制水需求，最大化细颗粒中的熟料成分，同时保持相似的整体粒度分布[171,172]。分开磨矿后再混合通常是优化各种成分相对粒度的更可取的技术。实现良好的粒度分布并尽量减少能量消耗的另一个重要因素是使用助磨剂[173]。

There is currently no equipment designed specifically for grinding multi-component cements, other than that those used for actual cement plant. Depending on the process and intended application, the used SCMs may already have a very fine particle size (e.g., calcined clays). However, grinding may be required to de-agglomerate clusters, decreasing the average diameter.
目前没有专门用于研磨多组分水泥的设备，除了实际水泥厂使用的设备。根据工艺和预期应用，所使用的矿物掺合料可能已经具有非常细的颗粒尺寸（例如，煅烧粘土）。然而，研磨可能是必要的，以去除团聚体，降低平均直径。

Since cement in separate grinding process is made by combining components that have been ground separately and because one of the primary goals of using an SCM is to reduce the carbon footprint of cement production, it is critical not to overlook the other process-based emissions. Comminution and grinding consume a significant amount of electricity in cement production. The lower electricity demand from grinding by optimized grinding process

[173, 174]

is a potential ancillary benefit of multi-component cements.
由于在分开研磨过程中，水泥是通过将单独研磨的成分结合而成的，并且使用矿物掺合料的主要目标之一是减少水泥生产的碳足迹，因此，不能忽视其他基于过程的排放。破碎和研磨在水泥生产中消耗了大量电力。通过优化研磨过程降低的研磨电力需求

[173, 174]

是多组分水泥的一个潜在附加好处。

The different constituents are normally ground separately in most research studies in academic laboratories involving blended cements. On the contrary, the most common grinding process in cement plants is based on co-grinding of cement constituents in closed circuit units. The main distinction between separate grinding and co-grinding is that different minerals interact inside the mill during co-grinding. These interactions between the different minerals in co-grinding process are primarily caused by their differences in grindability. These interactions prevent harder materials from further reducing particle size. Calcined clay and limestone have higher grindability (softer particles) than clinker that is softer than slag in blended cements. Knowing that clinker is the component providing performance at early age, certain attention to its PSD should be given to extract the most benefit out of it. If the SCMs are of a softer nature (e.g., limestone, calcined clays), clinker tends to remain concentrated in the coarse fraction after co-grinding, which may compromise the early age strength. Softer materials become much finer potentially reducing workability. So far, the highest reactivity of blended cement has been obtained when clinker is ground separately from SCMs.
在涉及混合水泥的学术实验室的大多数研究中，不同的成分通常是单独研磨的。相反，水泥厂中最常见的研磨过程是基于在闭路系统中共同研磨水泥成分。单独研磨和共同研磨之间的主要区别在于，在共同研磨过程中，不同的矿物在磨机内相互作用。这些矿物在共同研磨过程中的相互作用主要是由于它们在可磨性上的差异。这些相互作用阻止了更硬材料进一步减小颗粒尺寸。煅烧粘土和石灰石的可磨性（较软颗粒）高于熟料，而熟料又比混合水泥中的矿渣软。知道熟料是提供早期性能的成分后，应特别关注其粒度分布，以便最大限度地发挥其效益。如果矿物掺合料的性质较软（例如，石灰石、煅烧粘土），则在共同研磨后，熟料往往会集中在粗颗粒中，这可能会影响早期强度。较软的材料变得更加细小，可能会降低可加工性。到目前为止，当熟料与矿物掺合料分开研磨时，混合水泥的最高反应性已被获得。

Grinding aids are incorporated during clinker comminution to increase the fineness of the materials for a given specific energy consumption of the grinding mill [36]. Alkanolamine-based grinding aids promote the hydration of clinker aluminate phases (

C_{3} A

and ferrite) in composite cements, resulting in an increased carboaluminate precipitation as discussed in minor’s paragraph.
在熟料粉碎过程中加入助磨剂，以提高在给定特定能耗下磨机材料的细度[36]。基于醇胺的助磨剂促进复合水泥中熟料铝酸盐相（

C_{3} A

和铁酸盐）的水化，导致碳铝酸盐沉淀增加，如小节中所述。

Recent studies by Bolte et al

[47, 171]

showed that the increase of the clinker fineness has a pronounced impact on the strength. The maximal calculated compressive strength increases from 29 MPa to more than 48 MPa. Their results showed that grinding cement clinker increases strength for compositions rich in clinker by 20 MPa at 2 days of hydration, or similarly to the slag scenario. Still, the clinker’s Blaine grows by just

1500 {cm}^{2} / g

whereas the slag’s increases from 3000 to

5000 {cm}^{2}

/ g. As a result, while aiming to boost the early compressive strength, cement clinker grinding is more effective. Additionally increasing the clinker fineness in slag cement, allows increasing the content of limestone up to

15 - 20 %

without the significant reduction of the compressive strength. Optimizing component fineness in terms of hydration, microstructure, and performance is critical for maximizing the efficiency of
最近，Bolte 等人的研究显示，熟料细度的增加对强度有显著影响。计算得出的最大抗压强度从 29 MPa 增加到超过 48 MPa。他们的结果表明，磨细水泥熟料可以使富含熟料的配方在 2 天水化时强度增加 20 MPa，类似于矿渣的情况。然而，熟料的布莱恩值仅增长了，而矿渣的则从 3000 增加到/克。因此，在提高早期抗压强度的同时，水泥熟料的磨细更为有效。此外，在矿渣水泥中增加熟料细度，可以在不显著降低抗压强度的情况下，将石灰石的含量提高到。优化成分细度在水化、微观结构和性能方面对于最大化效率至关重要。
component materials in cement blends [43,46,171]. These findings allowed an optimal synergy between specific clinker, slag and limestone. The optimized fineness maximizes the reactivity of blended cements. Finer particles do not necessarily lead to a greater degree of ternary cement reaction. Optimized cement PSD as a function of the component’s chemistry can open new routes for reducing the Portland cement fraction in composite cements for equivalent reaction kinetics and/or strength.
水泥混合物中的组分材料[43,46,171]。这些发现使特定的熟料、矿渣和石灰石之间实现了最佳协同。优化的细度最大化了混合水泥的反应性。更细的颗粒不一定会导致三元水泥反应的更大程度。根据组分化学的优化水泥粒度分布可以为减少复合水泥中波特兰水泥的比例开辟新的途径，以实现等效的反应动力学和/或强度。

In composite cements, the clinker fineness has the greatest impact on hydration, setting time, phase assemblage evolution, and strength development

[46, 47]

. The fineness of the limestone has a minor impact on the heat of hydration and the setting time in ternary systems in the early hours of hydration. However, it improves the compressive strength at early age and maintains it over the entire duration given enough reactive components in the blends. In contrast, it is inefficient to mix slag with coarser clinker and limestone. The benefits of finer constituents in terms of hydration and compressive strength are realized at early age but reduce over longer hydration times. Increasing the fineness of the constituent materials necessitates careful consideration of the interdependencies between the various components.
在复合水泥中，熟料的细度对水化、凝结时间、相组分演变和强度发展影响最大。石灰石的细度对三元体系在水化初期的水化热和凝结时间影响较小。然而，它在早期提高了抗压强度，并在整个过程中保持这一强度，只要混合物中有足够的反应成分。相比之下，将粗颗粒熟料和石灰石与矿渣混合效率较低。细颗粒成分在水化和抗压强度方面的好处在早期显现，但在较长的水化时间内会减少。提高成分材料的细度需要仔细考虑各个成分之间的相互依赖关系。

4. Performance 4. 性能

4.1. Rheology 4.1. 流变学

Almost all concretes must meet workability as well as strength criteria (and maybe also durability). These requirements are somewhat antagonistic, because simply adding more water improves workability while decreasing strength. This interaction, however, has become more complex in recent decades as admixture technology has advanced. Unfortunately, some new SCMs (e.g., natural pozzolans) require a low water to cement ratio to achieve the required strength and durability, with minimum cement content. However, it is almost impossible to ensure good workability without admixtures. As a result, a large proportion of concrete containing high SCMs proportions and less clinker (and thus emitting less

{CO}_{2}

) can most likely not be made without admixtures.
几乎所有混凝土都必须满足可加工性和强度标准（可能还有耐久性）。这些要求在某种程度上是对立的，因为简单地增加水分可以改善可加工性，但会降低强度。然而，随着近年来外加剂技术的发展，这种相互作用变得更加复杂。不幸的是，一些新的矿物掺合料（例如天然火山灰）需要低水泥比以达到所需的强度和耐久性，同时水泥含量最小。然而，几乎不可能在没有外加剂的情况下确保良好的可加工性。因此，含有高比例矿物掺合料和较少熟料（因此排放更少

{CO}_{2}

）的混凝土很可能无法在没有外加剂的情况下制造。

To reduce water leads to a reduction of the paste volume at an equal cement dosage. As the volume of paste decreases, rheological difficulties become more pronounced. All of this makes rheology an important research area, particularly for low paste volume concretes, where they tend to be stickier, flow more slowly (higher viscosity), and may segregate if not properly admixed [175-178]. An optimized particle size distribution of the cement in addition to a proper aggregate grading allow lower water demand and a good workability without relying too much on admixtures for flow correction and limit the robustness issues caused by material fluctuations.
减少水分会导致在相同水泥用量下浆体体积的减少。随着浆体体积的减少，流变学问题变得更加明显。这使得流变学成为一个重要的研究领域，特别是对于低浆体体积的混凝土，这些混凝土往往更粘稠，流动速度较慢（粘度较高），如果没有适当混合可能会发生分离。优化水泥的颗粒大小分布以及适当的骨料级配可以降低水的需求，并在不过度依赖外加剂进行流动修正的情况下，保持良好的可加工性，同时限制由材料波动引起的稳健性问题。

The rheological behavior of concrete is a multiscale and multitimescale problem. The discussion here focuses rather on the microscale (paste level), where flocculation or dispersion of particles suspended in the pore solution for a given volume fraction will affect the rheological properties at the concrete level. Flocculation and dispersion processes dominate at short timescales, whereas the overall hydration process leads to the irreversible transition of a granular fluid to a fully percolated solid over a longer time frame [178-183]. Composite cements with significantly SCMs contents having a higher specific surface than cement, and especially irregular particle shapes with voids, result in inferior rheology when compared to ordinary cements.
混凝土的流变行为是一个多尺度和多时间尺度的问题。这里的讨论主要集中在微观尺度（浆体水平），在给定体积分数下，悬浮在孔隙溶液中的颗粒的絮凝或分散将影响混凝土水平的流变特性。絮凝和分散过程在短时间尺度上占主导地位，而整体水化过程则在更长的时间范围内导致颗粒流体向完全渗透固体的不可逆转变[178-183]。与普通水泥相比，含有显著矿物掺合料（SCMs）成分的复合水泥具有更高的比表面积，尤其是具有空隙的不规则颗粒形状，导致其流变性较差。

The impact of all concrete matrix components (i.e. cement type, SCMs and mineral fillers) on the rheology was published by several researchers[184,185]. When using limestone as filler, the addition of limestone filler induces a greater hydration stimulation of the

C_{3} A

/ aluminate fraction, which results in a higher yield stress overall. The viscosity and yield stress of Portland cement fresh paste are determined by its qualitative and its quantitative mineralogical and chemical composition, especially the cement’s

{Na}_{2} Oeq

. (%) content [186], i.e., the
所有混凝土基体成分（即水泥类型、矿物掺合料和矿物填料）对流变学的影响已被多位研究者发表。当使用石灰石作为填料时，添加石灰石填料会引起更强的水化刺激，导致铝酸盐部分的水化，从而整体上产生更高的屈服应力。波特兰水泥新鲜浆体的粘度和屈服应力由其定性和定量的矿物学及化学成分决定，特别是水泥的含量。
alkaline element content in the liquid phase of their fresh paste, as well as the amount and types of hydrated compounds generated during the hydration latency period, when the fresh paste is fluid. This stimulating effect prevailed over the physical dilution of the PC by the limestone filler, as well as the associated effect of the chemical dilution of the paste’s liquid phase and its main constituents, portlandite and

{Na}_{2} O_{eq}

[186].
新鲜浆体液相中的碱性元素含量，以及在新鲜浆体流动时水合潜伏期内生成的水合化合物的数量和类型。这种刺激效应超过了石灰石填料对水泥浆的物理稀释效应，以及水泥浆液相及其主要成分（氢氧化钙和

{Na}_{2} O_{eq}

）的化学稀释效应[186]。

Siliceous fly ash (FA) is a special SCM with respect to rheology. Despite a lower density than OPC and increased volume of the solid with replacing OPC by mass, the flow resistance data in literature shows a steady decrease with increasing replacement of OPC by FA. The decrease in flow resistance is caused by the spherical nature of FA as well as its low reactivity[184,187-189]. Additionally, if low carbon content is present in the FA, there is much lower interaction of the plasticizers, so the effective plasticizer-to-cement ratio is increasing and thereby also the retardation of the cement can be observed[190]. The situation with slag is a bit more complex than FA. The surface of slag has calcium-sites capable of coordinating with plasticizers, unlike the siliceous fly ash, but to a lesser extent than OPC. However, little interaction is observed and the behaviors of slag blended cement and OPC neat cement with comparable PSD are similar.
硅酸盐粉煤灰（FA）是一种特殊的矿物掺合料，具有独特的流变特性。尽管其密度低于普通波特兰水泥（OPC），并且用 FA 按质量替代 OPC 会增加固体体积，但文献中的流动阻力数据表明，随着 FA 替代 OPC 的比例增加，流动阻力稳步下降。流动阻力的降低是由于 FA 的球形特性以及其低反应性[184,187-189]。此外，如果 FA 中含有低碳含量，塑化剂的相互作用会大大降低，因此有效的塑化剂与水泥的比例增加，从而也可以观察到水泥的延缓现象[190]。与 FA 相比，矿渣的情况要复杂一些。矿渣的表面具有能够与塑化剂配位的钙位点，这与硅酸盐粉煤灰不同，但程度低于 OPC。然而，观察到的相互作用很少，矿渣掺合水泥和具有可比粒度分布的 OPC 净水泥的行为相似。

The most complicated situation concerns the use of calcined clays [191-195] and natural pozzolans[196-199]. The surface available is increased dramatically and the water demand of the mixes is high especially that no clear strategy of composite cement manufacturing is present. The interaction between the sulfate-silicate-aluminate-alkalis balance to understand the hydration-rheology link with high SCMs content binders is missing. Additionally, many chemical bonds are broken during the clay calcination. Calcined clays, as a result, have irregular atomic arrangements and a thermodynamically stable state with a high surface energy. At the same time, its internal structure contains many pores, for which some nano calcined clays exhibit strong pozzolanic activity during the concrete stirring process.
最复杂的情况涉及到煅烧粘土[191-195]和天然火山灰[196-199]的使用。可用表面积显著增加，混合物的水需求量很高，尤其是目前没有明确的复合水泥制造策略。缺乏对硫酸盐-硅酸盐-铝酸盐-碱平衡的相互作用的理解，以便理解高掺量矿物掺合料与水化-流变学之间的联系。此外，在粘土煅烧过程中，许多化学键被打破。因此，煅烧粘土具有不规则的原子排列和热力学稳定状态，具有高表面能。同时，其内部结构包含许多孔隙，因此一些纳米煅烧粘土在混凝土搅拌过程中表现出强的火山灰活性。

4.2. Optimum sulfate 4.2. 最优硫酸盐

It is well known that the calcium sulfate is added into cement to avoid flash setting and extend the period of workability that needed to place the concrete, by controlling the hydration of

C_{3} A

[200,201]. Two main hypotheses have been proposed to explain why the calcium sulfate slows down the hydration of

C_{3} A

. On one hand, it has been attributed to the barrier effect that arises from the formation of ettringite or AFm phases around the

C_{3} A

surfaces [202-204]. Nevertheless, Scrivener and Pratt [205] reported that the morphology of ettringite is unlikely to act as a substantial barrier to ion transport. Also, Minard et al [204] showed that the early hydration of

C_{3} A

with gypsum results in the formation of AFm phases, which is also formed without gypsum and shows no retardation effect on

C_{3} A

hydration. On the other hand, some authors believe that the adsorption of calcium and sulfate ions on the active dissolution sites of

C_{3} A

is the main cause for retardation of

C_{3} A

hydration [204,206]. Although there is still no consensus on these mechanisms, the amount of optimum calcium sulfate required to be added into cement for delaying the

C_{3} A

hydration needs to be properly studied as it can influence the mechanical properties of cement at early stages [159,207,208]. The optimum sulfate content in cement can be determined using isothermal calorimetry and compressive strength tests by varying calcium sulfate content, as described in ASTM C 563 standard.
众所周知，硫酸钙被添加到水泥中以避免快速凝结，并延长浇筑混凝土所需的可操作时间，通过控制

C_{3} A

的水化[200,201]。提出了两个主要假设来解释为什么硫酸钙会减缓

C_{3} A

的水化。一方面，这被归因于在

C_{3} A

表面周围形成的艾特林石或 AFm 相所产生的屏障效应[202-204]。然而，Scrivener 和 Pratt[205]报告称，艾特林石的形态不太可能对离子运输形成实质性屏障。此外，Minard 等[204]显示，石膏与

C_{3} A

的早期水化会导致 AFm 相的形成，而在没有石膏的情况下也会形成，并且对

C_{3} A

的水化没有延缓作用。另一方面，一些作者认为，钙和硫酸根离子在

C_{3} A

的活性溶解位点上的吸附是导致

C_{3} A

水化延缓的主要原因[204,206]。尽管对这些机制仍未达成共识，但需要对延迟水合所需添加到水泥中的最佳硫酸钙量进行适当研究，因为这会影响水泥在早期阶段的机械性能[159,207,208]。可以通过等温量热法和抗压强度测试来确定水泥中的最佳硫酸盐含量，方法是改变硫酸钙含量，如 ASTM C 563 标准所述。

The optimum sulfate content in cement is mainly influenced by factors that affect the formation of ettringite and C-S-H, as these are the two main hydration products that consume sulfates in cement [208]. The main factors that increase the ettringite and C-S-H formation at early ages and thus optimum sulfate content are 1) physical and chemical composition of the clinker, 2) type of sulfate sources used in cement and 3) SCMs.
水泥中最佳硫酸盐含量主要受影响水合产物等钙铝石和 C-S-H 形成的因素影响，因为这两种是消耗水泥中硫酸盐的主要水合产物[208]。在早期增加等钙铝石和 C-S-H 形成的主要因素，从而达到最佳硫酸盐含量包括：1）熟料的物理和化学成分，2）水泥中使用的硫酸盐来源类型，以及 3）矿物掺合料。

The increase in clinker fineness accelerates the precipitation of both ettringite and C-S-H. As a result, increase in clinker fineness accelerates
熟料细度的增加加速了艾特林石和 C-S-H 的沉淀。因此，熟料细度的增加加速了。
the sulfate depletion and demands more optimum sulfate content [208]. Similarly, the increase in

C_{3} A

and

C_{3} S

leads to higher optimum sulfate content, as both enhance the formation of ettringite and C-S-H respectively

[208, 209]

. Although the increase in

C_{4} AF

may require more sulfate, its influence is lower due to its low reactivity. Alkali-content is another factor that influences the sulfate demand in cement. An increase in alkali-content has been reported to result in a higher sulfate demand due to precipitation of more C-S-H and accelerating the

C_{3} S

and increased in orth

- C_{3} A /

cub-

C_{3} A

ratio [208,210].
硫酸盐的耗竭需要更优的硫酸盐含量[208]。类似地，

C_{3} A

和

C_{3} S

的增加导致更高的最佳硫酸盐含量，因为两者分别增强了水硬石和 C-S-H 的形成

[208, 209]

。尽管

C_{4} AF

的增加可能需要更多的硫酸盐，但由于其反应性较低，其影响较小。碱含量是影响水泥硫酸盐需求的另一个因素。已报道碱含量的增加会导致更高的硫酸盐需求，因为这会导致更多 C-S-H 的沉淀，并加速

C_{3} S

以及正交

- C_{3} A /

立方

C_{3} A

比的增加[208,210]。

Generally, both the

{SO}_{3}

content and sulfates solubility influences the sulfate optimization in cement. A sulfate source with higher amounts of

{SO}_{3}

might lower the solid sulfate content required to have proper sulfated cement [210]. On the other hand, an increase in sulfate solubility increases the required optimum sulfate content in cement. The solubility of sulfates mainly depends on the chemical/mineralogy composition of sulfate source used. Gypsum

({Ca}_{2} {SO}_{4} 2 H_{2} O)

, hemihydrate

({Ca}_{2} {SO}_{4} 1 / 2 H_{2} O)

and anhydrite

({Ca}_{2} {SO}_{4})

are the three most used calcium sulfate sources in cement. Their solubility is in order of hemihydrate

>

gypsum

>

anhydrite. Also, the fineness of the sulfate source plays a role in sulfate solubility. A recent study [211] reported that cement with fine gypsum reaches sulfate depletion sooner and demands more sulfates.
一般来说，

{SO}_{3}

的含量和硫酸盐的溶解度影响水泥中的硫酸盐优化。含有较高量的

{SO}_{3}

的硫酸盐源可能会降低所需的固体硫酸盐含量，以获得适当的硫酸盐水泥 [210]。另一方面，硫酸盐溶解度的增加会提高水泥中所需的最佳硫酸盐含量。硫酸盐的溶解度主要取决于所用硫酸盐源的化学/矿物组成。石膏

({Ca}_{2} {SO}_{4} 2 H_{2} O)

、半水石膏

({Ca}_{2} {SO}_{4} 1 / 2 H_{2} O)

和无水石膏

({Ca}_{2} {SO}_{4})

是水泥中使用的三种最常见的硫酸钙源。它们的溶解度顺序为半水石膏

>

、石膏

>

、无水石膏。此外，硫酸盐源的细度也会影响硫酸盐的溶解度。最近的一项研究 [211] 报告称，细石膏的水泥更快达到硫酸盐耗竭，并且需要更多的硫酸盐。

In addition to the sulfate ions, the cations (

Ca, Na, K, Mg

) of the solid sulfate source used also have shown influence on

C_{3} A

hydration and consequently on optimum sulfate content [212]. Recent researchers [212] has shown that compared to Ca-sulfate, the use of Mg-sulfate lowers the time to sulfate depletion due to retardation of

C_{3} A

hydration and demands lower optimum sulfate content. Na-sulfate accelerates the

C_{3} A

and

C_{3} S

hydration and therefore increases the sulfate demand compared to Ca-sulfate.
除了硫酸根离子，所用固体硫酸盐源的阳离子（

Ca, Na, K, Mg

）也对

C_{3} A

水合产生了影响，从而影响了最佳硫酸盐含量[212]。最近的研究者[212]表明，与钙硫酸盐相比，使用镁硫酸盐降低了由于

C_{3} A

水合延迟而导致的硫酸盐耗竭时间，并且需要更低的最佳硫酸盐含量。钠硫酸盐加速了

C_{3} A

和

C_{3} S

水合，因此与钙硫酸盐相比，增加了硫酸盐需求。

Many researchers have reported that replacing cement (clinker + calcium sulfate) with different SCMs requires additional calcium sulfate on top of that contained in cement [210]. This increase in sulfate demand with SCM’s substitution is mainly attributed to two factors. It’s well known that the physical presence of the SCMs will enhance the reaction of clinker phases at early ages by providing the additional nucleation sites for hydration and increases the effective W/C ratio. As a result, a higher amount of hydrated C-S-H is precipitated and advances sulfate depletion by absorbing sulfates on its surface. Both the surface area and the amount of SCM substituted might influence the sulfate demand in blended cements, as they increases the hydration of

C_{3} S

and forms more C-S-H, which adsorb sulfate on it and advance sulfate depletion [213]. The formation of additional ettringite using dissolved alumina ions from SCMs in the first hours of hydration enhances the sulfate consumption and results in earlier sulfate depletion [210].
许多研究人员报告称，用不同的矿物掺合料（SCMs）替代水泥（熟料 + 硫酸钙）需要额外的硫酸钙，超出水泥中所含的量[210]。这种在 SCMs 替代过程中硫酸盐需求增加主要归因于两个因素。众所周知，SCMs 的物理存在会通过提供额外的水化成核位点来增强熟料相在早期的反应，并增加有效的水胶比。因此，沉淀出更多的水合 C-S-H，并通过在其表面吸收硫酸盐来加速硫酸盐的消耗。替代的 SCMs 的表面积和数量可能会影响混合水泥中的硫酸盐需求，因为它们增加了水化并形成更多的 C-S-H，从而在其上吸附硫酸盐并加速硫酸盐的消耗[213]。在水化的头几个小时内，利用 SCMs 中溶解的铝离子形成额外的钙铝石，增强了硫酸盐的消耗，并导致更早的硫酸盐消耗[210]。

A study using slags of the same fineness but with different alumina content showed that sulfate depletion occurs sooner with increasing alumina content [214]. Similarly, another study on the LC

^{3}

system with calcined clays containing different metakaolin content (reactive Al) showed that sulfate depletion occurs earlier for systems containing calcined clay with high metakaolin content, although it has lower fineness compared to others [66]. On the contrary Zunino and Scrivener [213] reported that only the fineness of calcined clays impacts the sulfate optimization rather than the alumina content of calcined clays in

{LC}^{3}

cements.
一项研究表明，使用相同细度但铝土矿含量不同的矿渣时，随着铝土矿含量的增加，硫酸盐耗竭发生得更早 [214]。类似地，另一项关于含有不同活性铝的煅烧粘土的 LC

^{3}

系统的研究显示，尽管其细度低于其他系统，但高活性铝含量的煅烧粘土系统的硫酸盐耗竭发生得更早 [66]。相反，Zunino 和 Scrivener [213] 报告称，只有煅烧粘土的细度影响硫酸盐的优化，而不是煅烧粘土的铝土矿含量在

{LC}^{3}

水泥中的影响。

The optimum sulfate content in blended cements increases with increasing limestone content due to its high filler effect compared to other SCMs. Nevertheless, some authors [28,215] reported that an increase in limestone content decreases the sulfate demand and attributes this to changes in phase assemblage. With limestone addition, both hemi-carboaluminate and mono-carboaluminate are favored instead of monosulfate and stabilizes the ettringite, thus decreasing the sulfate demand.
在混合水泥中，最佳硫酸盐含量随着石灰石含量的增加而增加，因为与其他矿物掺合料相比，石灰石具有较高的填充效果。然而，一些作者[28,215]报告称，石灰石含量的增加会降低硫酸盐需求，并将其归因于相组分的变化。随着石灰石的添加，半碳铝酸盐和单碳铝酸盐受到青睐，而不是单硫酸盐，并稳定了艾特林石，从而降低了硫酸盐需求。

Also, the sulfates present in SCMs might have an impact on the required solid sulfate source to have proper sulfate blended cement [210]. In addition to the above three factors, the chemical admixture,
此外，SCMs 中存在的硫酸盐可能会影响所需的固体硫酸盐来源，以获得适当的硫酸盐混合水泥[210]。除了上述三个因素，化学外加剂，
curing temperature and W/C ratio used might also have an impact on sulfate optimization, as they influence the cement hydration during early hours of the hydration.
固化温度和水胶比可能也会对硫酸盐优化产生影响，因为它们在水化的早期阶段影响水泥的水化。

4.3. Early age reactivity
4.3. 早期反应性

The early age strength of concrete determines how fast a structure can be built. Early age strength is particularly relevant for construction that are constrained by tight schedules (like bridges), or precast concretes as it influences the production rate. The early age strength of concrete can also affect its long-term durability. A concrete structure that achieves strength early will be less likely to suffer from poor curing condition, drying shrinkage and cracking over time, which can reduce its overall lifespan.
混凝土的早期强度决定了结构建造的速度。早期强度对于受紧迫时间限制的施工（如桥梁）或预制混凝土尤为重要，因为它影响生产速度。混凝土的早期强度还会影响其长期耐久性。早期达到强度的混凝土结构不太可能因养护条件差、干缩和开裂而受到影响，从而减少其整体使用寿命。

The strength of concrete, is dependent on a variety of factors, including the strength of the cement paste but also the amount and type of aggregates, the water-cement ratio, and the curing conditions. Because concrete is a composite material, its strength development is influenced by the interaction between the cement paste and the aggregates. Consequently, the levers that most improve the early age strength of concrete are not necessarily the same as the levers that improve the early age strength of cement.
混凝土的强度取决于多种因素，包括水泥浆的强度、骨料的种类和数量、水泥与水的比例以及养护条件。由于混凝土是一种复合材料，其强度的发展受到水泥浆与骨料之间相互作用的影响。因此，最能提高混凝土早期强度的因素不一定与提高水泥早期强度的因素相同。

The standard tests for mortar are the tests that control the performance of cement at a given temperature, sand grade/quantity, cement and water quantity though there are some differences in detail from one to another standard.
砂浆的标准测试是控制在特定温度下水泥性能的测试，包括砂的等级/数量、水泥和水的数量，尽管不同标准之间在细节上存在一些差异。

At the early age up to

\sim 2

days, it is the reaction of the clinker and not those of SCM that give the major contribution on the early age strength therefore, the low clinker cement often has low early age strength.
在早期阶段（最多

\sim 2

天），水泥熟料的反应而不是矿物掺合料的反应对早期强度的主要贡献，因此，低熟料水泥通常具有较低的早期强度。

As a consequence, the early strength improvement of low clinker cement is often done through an improvement of clinker reaction such as an increase of fineness of clinker, clinker composition, a sulfate requirement

[208, 216, 217]

and accelerators [111,218-221]. In very low clinker cement, the improvement based on clinker reaction becomes less effective simply because there is not enough clinker.
因此，低熟料水泥的早期强度提高通常是通过改善熟料反应来实现的，例如增加熟料的细度、熟料成分、硫酸盐需求

[208, 216, 217]

和加速剂[111,218-221]。在非常低熟料水泥中，基于熟料反应的改善效果变得不那么明显，因为熟料的数量不足。

The reaction of pozzolanic SCMs at an early age can be improved by soluble alkali [222-224], however, it has been known for long that this lever often decreases 28 days of strength of Portland cement [225]. Moreover, the durability of the concrete activated by such a solution might be questionable especially regarding alkali aggregate reaction because of the resulting high soluble alkali content in pore solution.
火山灰矿物的早期反应可以通过可溶性碱来改善[222-224]，然而，早已知道这种添加剂往往会降低波特兰水泥的 28 天强度[225]。此外，由这种溶液激活的混凝土的耐久性可能值得怀疑，特别是在碱-骨料反应方面，因为孔隙溶液中会产生高可溶性碱含量。

The early age strength of low clinker concrete still depends very much on the early age strength of low clinker cement. Nevertheless, other additional levers or parameters must be considered. Key parameters such as porosity, particle packing, and temperature are discussed below.
低熟料混凝土的早期强度仍然在很大程度上依赖于低熟料水泥的早期强度。然而，还必须考虑其他额外的杠杆或参数。以下讨论了孔隙率、颗粒堆积和温度等关键参数。

The first lever is the decrease of the initial porosity which is defined by the water to binder ratio To decrease the water to binder ratio an optimum packing of solid particles [226] and superplasticizers are essential. The optimum packing density decreases the volume of water trapped between particles therefore, so that more water is available for the rheology. The superplasticizer decreases the yield stress and in some cases viscosity of fresh concrete especially the concrete with low initial water content; therefore, the fresh concrete can have a better flow even with low water content. A low initial porosity can compensate for a low cement reaction of cement as illustrated by ultra-high performance concrete (UHPC) where 90 MPa compressive strength can be achieved at 1 day.
第一个杠杆是初始孔隙率的降低，这由水与胶结材料的比例定义。为了降低水与胶结材料的比例，固体颗粒的最佳堆积和超塑化剂是必不可少的。最佳堆积密度减少了颗粒之间被困水的体积，因此更多的水可用于流变学。超塑化剂降低了新混凝土的屈服应力，在某些情况下还降低了粘度，特别是对于初始水含量较低的混凝土；因此，即使水含量较低，新混凝土也能具有更好的流动性。低初始孔隙率可以弥补水泥的低反应性，如超高性能混凝土（UHPC）所示，在 1 天内可以达到 90 MPa 的抗压强度。

The second lever consists in increasing the curing temperature. Both cement hydration and SCM pozzolanic reactions benefit from temperature. The apparent activation energy of SCM pozzolanic reaction is larger than the one of clinker hydration reaction [227,228]. This lever is often used in precast concrete.
第二个杠杆是提高固化温度。水泥水化和矿物掺合料的火山灰反应都受益于温度。矿物掺合料火山灰反应的表观活化能大于熟料水化反应的表观活化能[227,228]。这个杠杆通常用于预制混凝土。

Finally, the volume efficiency of reactions (ratio of volume of hydrates to the volume of reacted binder) also contributes. The volume efficiency of hydrates to clinker is about 1.5 to 2 . Nevertheless, the
最后，反应的体积效率（水合物体积与反应结合料体积的比率）也起到了一定的作用。水合物与熟料的体积效率约为 1.5 到 2。然而，
addition of small amounts of other binders with a higher volume efficiency than the one of clinker can also improve early strength development

[229, 230]

. Therefore, at a given degree of reaction, there is higher volume of hydrates and a lower porosity.
添加少量体积效率高于熟料的其他粘合剂也可以改善早期强度发展

[229, 230]

。因此，在给定的反应程度下，水合物的体积更大，孔隙率更低。

4.4. Late age reactivity 4.4. 晚期反应性

The performance of composite cement at late ages is mainly governed by the extent of the reaction of the added SCMs. Clinker phases at low clinker level

(< 0.6)

reacts almost fully (except belite and Ferrite) within the first week of hydration. Scrivener and co-workers studied the hydration of cements at later hydration times [49,66,231-233]. They demonstrated that hydrates gradually fill the pore space of ordinary Portland cements and composite cements during hydration, resulting in porosity reduction and refinement. Muller et al. [234,235] used

^{1} H

NMR to demonstrate that the volume of water-filled capillary pores decreases rapidly after the first day of hydration. In parallel, the volume of gel pores increases. As a result, the hydrates precipitate in small pores (tens of nanometers in size), especially at lower water-to-cement ratios. The hydrates formed must be smaller to precipitate or grow into the small water-filled pores. According to mercury intrusion porosimetry, after about 28 days of hydration, the porosity of composite cements containing slag or fly ash hydrated at a water to binder (w/b) ratio of approximately 0.4 is no longer refined, as described by the constant critical pore entry radius [231,236]. This critical pore radius of approximately 3 to 5 nm can be reached as early as 3 days in the system containing reactive metakaolin [66]. It has been proposed that this phenomenon is related to a slowing of hydration. However, at w/b of 0.5 or higher no such stopping of hydration is observed despite the critical size reached [49,63,154,237].
复合水泥在后期的性能主要受添加的矿物掺合料（SCMs）反应程度的影响。在低熟料水平下（

(< 0.6)

），熟料相在水化的第一周几乎完全反应（除了贝利特和铁铝矿）。Scrivener 及其同事研究了水泥在后期水化时间的水化过程[49,66,231-233]。他们证明，在水化过程中，水合物逐渐填充普通波特兰水泥和复合水泥的孔隙空间，从而导致孔隙率降低和细化。Muller 等人[234,235]使用

^{1} H

NMR 证明，水化第一天后，充满水的毛细孔体积迅速减少。与此同时，胶体孔的体积增加。因此，水合物在小孔（尺寸在几十纳米）中沉淀，特别是在较低的水胶比下。形成的水合物必须更小，以便在小的充水孔中沉淀或生长。根据汞压入法测定，经过大约 28 天的水化，含有矿渣或粉煤灰的复合水泥在水与胶结材料（w/b）比约为 0 时的孔隙率。4 不再精炼，如常数临界孔入口半径所描述的[231,236]。在含有反应性高岭土的系统中，这一约为 3 到 5 纳米的临界孔半径可以在 3 天内达到[66]。有人提出这一现象与水化速率减缓有关。然而，在水胶比为 0.5 或更高时，尽管达到了临界尺寸，却没有观察到水化停止的现象[49,63,154,237]。

Because the microstructure is constantly refined during hydration, the C-S-H precipitates in increasingly confined spaces. This necessitates an increase in supersaturation for the C-S-H phase to account for the decrease in pore size, assuming that hydration is limited by hydrate growth. However, the supersaturation of the C-S-H phase appears to be a function of the alkali concentration in the solution rather than pore space refinement [154]. The limited changes in C-S-H phase saturation indexes between about 0.5 and 1 year of hydration suggest that the mechanism of C-S-H phase growth does not change during this period, even though the available space for growth decreases and refines significantly. Because it is unlikely that the space available limits hydration at the early stages of hydration, i.e., at times 0.1 to 0.5 days, and the saturation indexes do not change, it is reasonable to conclude that the space available does not limit the precipitation of C-S-H and thus the hydration at later stages. The concentration of alkalis in the pore solution affects the tension in the pore solution and thus the growth of the C -S-H phase. Thermodynamically incompatible phases (e.g. portlandite and strätlingite) coexist in systems such as composite cements with highly reactive calcined clays [68]. This implies that the compositions of the local pore solutions must differ. More progress in characterization techniques and modeling tools is required to advance our understanding of such heterogeneous cement pastes.
由于在水化过程中微观结构不断被精炼，C-S-H 在越来越狭窄的空间中沉淀。这需要增加 C-S-H 相的过饱和度，以适应孔隙尺寸的减小，假设水化是由水合物的生长所限制。然而，C-S-H 相的过饱和度似乎是溶液中碱浓度的函数，而不是孔隙空间的精炼[154]。在大约 0.5 到 1 年的水化过程中，C-S-H 相饱和指数的有限变化表明，尽管可用的生长空间显著减少和精炼，但 C-S-H 相生长的机制在此期间并没有改变。因为在水化的早期阶段，即 0.1 到 0.5 天时，可用空间不太可能限制水化，并且饱和指数没有变化，因此可以合理地得出结论：可用空间并不限制 C-S-H 的沉淀，因此也不限制后期的水化。孔隙溶液中碱的浓度影响孔隙溶液中的张力，从而影响 C-S-H 相的生长。热力学上不相容的相（例如。波特兰石和斯特拉廷石在复合水泥与高反应性煅烧粘土的系统中共存[68]。这意味着局部孔隙溶液的成分必须不同。需要在表征技术和建模工具方面取得更多进展，以加深我们对这种异质水泥浆的理解。

Briki et al. [49] demonstrated that after about 7 days of hydration of slag cement, RH drops below

90 %

w / c = 0.4

. Similar results have been reported for metakaolin-containing composite cements [63]. At RH less than

100 %

, water begins to evaporate in the porous body of the cement paste, and menisci form in the pore space [238,239]. This causes the capillary pressure to form because of the interaction between the solution and the walls of the pores, as well as the emptying of the larger pores. The decrease in relative humidity is caused by cement paste selfdesiccation and a decrease in water activity in the pore solution caused by rising alkali concentrations in the pore solution. It is important to note that only the first contribution increases the pore solution tension [240] and modifies the pressure in the crystal.
Briki 等人 [49] 证明，在约 7 天的矿渣水泥水化后，相对湿度降至

90 %

在

w / c = 0.4

。对于含有高岭土的复合水泥也有类似的结果 [63]。在相对湿度低于

100 %

时，水开始在水泥浆的多孔体内蒸发，并在孔隙空间中形成弯月面 [238,239]。这导致毛细压力的形成，因为溶液与孔壁之间的相互作用，以及较大孔隙的排空。相对湿度的降低是由于水泥浆的自干燥和孔隙溶液中水活性的降低，这种降低是由于孔隙溶液中碱浓度的上升。值得注意的是，只有第一个因素会增加孔隙溶液的张力 [240] 并改变晶体内的压力。

However, the macroscopic formation (precipitation) of C-S-H phase is caused by nanoparticle aggregation[241]. This is because the growth
然而，C-S-H 相的宏观形成（沉淀）是由纳米颗粒聚集引起的[241]。这是因为生长
rate of highly charged C-S-H particles is significantly slower than the rate of heterogeneous nucleation[241,242]. Knowing that the surface properties of the C-S-H phase are very similar to those of

C_{3} S

, i.e., the hydroxylated calcium silicate surface, one can argue that secondary nucleation of C-S-H (that is, nucleation of new C-S-H particles close to an existing C-S-H particle) is dominant. The conditions in the pore solution favors heterogeneous nucleation of new C-S-H particles over the growth of already existing C-S-H particles. The alkalis partially replace calcium at the surface of the C-S-H phase under higher alkali concentrations and lower calcium concentration. This influences the interaction free energy at contact between C-S-H particles [243] and, as a result, the heterogeneous nucleation rate of C-S-H. A higher supersaturation is required at higher alkali concentrations to achieve the same rate of C-S-H precipitation.
高电荷 C-S-H 颗粒的形成速率显著低于异质成核的速率[241,242]。考虑到 C-S-H 相的表面特性与

C_{3} S

（即羟基化钙硅酸盐表面）非常相似，可以认为 C-S-H 的二次成核（即在现有 C-S-H 颗粒附近形成新的 C-S-H 颗粒）是主导的。孔溶液中的条件更有利于新 C-S-H 颗粒的异质成核，而不是已有 C-S-H 颗粒的生长。在较高的碱浓度和较低的钙浓度下，碱部分取代 C-S-H 相表面的钙。这影响了 C-S-H 颗粒接触时的相互作用自由能[243]，从而影响 C-S-H 的异质成核速率。在较高的碱浓度下，需要更高的过饱和度才能达到相同的 C-S-H 沉淀速率。

The slowing of dissolution, precipitation and species transport from the dissolution surface to the precipitation surface, controls the overall rate of the hydration reaction. Until now, the effect of transportation has been overlooked. During the hydration of calcium silicates, a shell of hydration products forms around the anhydrous grains [201]. As a result, the elements must dissolve and diffuse across the hydration products (the so-called inner product) to the space where the hydrates precipitate (the so-called outer product).
溶解、沉淀和物种从溶解表面到沉淀表面的运输速度减缓，控制了水合反应的整体速率。到目前为止，运输的影响一直被忽视。在钙硅酸盐的水合过程中，水合产物的壳层在无水颗粒周围形成[201]。因此，元素必须在水合产物（所谓的内产物）中溶解并扩散到水合物沉淀的空间（所谓的外产物）。

If the ion transport is slower than the dissolution and precipitation processes, the concentrations in the space near the dissolving anhydrous particles would be higher than in the space near the outer product. This process results in higher supersaturation of hydrates (C-S-H) and lower undersaturation against anhydrous phases. The presence of higher supersaturation in the space close to the anhydrous material is supported by the fact that the inner C-S-H phase has a finer microstructure, i.e., it has a smaller crystal size, than the outer product. Metakaolin-containing cements are another illustration of the effect of the slow transport on the evolution of the microstructure. The presence of thermodynamically incompatible phases, namely portlandite and strätlingite in these systems

[35, 68]

, or the limited reaction of dolomite in the presence of portlandite [32] is another illustration of the differences in local concentration in the cementitious systems. However, the total porosity decreases steadily even in samples with fine microstructure [32,63]. when the pore threshold diameter does not decrease further or when incompatible phase assemblage is present. This demonstrates that the hydration is still taking place, but its rate is limited by most probably the transport phenomenon from dissolving sites to precipitation sites.
如果离子运输速度慢于溶解和沉淀过程，那么在溶解的无水颗粒附近的空间中的浓度将高于外部产物附近的空间。这一过程导致水合物（C-S-H）的过饱和度更高，而无水相的不足饱和度更低。在靠近无水材料的空间中存在更高的过饱和度，这一事实得到了内层 C-S-H 相具有更细微观结构的支持，即其晶体尺寸小于外部产物。含有高岭土的水泥是慢运输对微观结构演变影响的另一个例证。这些系统中存在热力学不相容相，即波特兰石和斯特拉丁石，或者在波特兰石存在下白云石的反应有限[32]，是水泥系统中局部浓度差异的另一个例证。然而，即使在具有细微观结构的样品中，总孔隙率也在稳步下降[32,63]，当孔径阈值直径不再进一步降低或存在不相容相组合时。这表明水合仍在进行，但其速率很可能受到从溶解点到沉淀点的传输现象的限制。

4.5. SCM reactivity 4.5. SCM 反应性

Incorporating SCMs in cement affects the hydration kinetics and phase assemblage in various ways. Firstly, the physical presence of SCM in cement provides more surface area for precipitation of hydrates, commonly known as filler effect. Secondly, the SCM can chemically react and form cementitious compounds, which affect the microstructure and strength. Therefore, the development of low-clinker cements with increasing SCM content is closely linked to the reactivity of SCMs and their effect on microstructure development. In this context, different testing methods (both direct and indirect) to quantify the SCM reactivity in cement have been reviewed by many authors [244-246].
在水泥中加入矿物掺合料（SCMs）以多种方式影响水化动力学和相组成。首先，SCM 在水泥中的物理存在提供了更多的表面积用于水合物的沉淀，通常称为填充效应。其次，SCM 可以发生化学反应，形成水泥化合物，从而影响微观结构和强度。因此，随着 SCM 含量的增加，低熟料水泥的发展与 SCM 的反应性及其对微观结构发展的影响密切相关。在这种背景下，许多作者对定量评估水泥中 SCM 反应性的不同测试方法（包括直接和间接方法）进行了综述[244-246]。

Selective dissolution methods are the most commonly used method to directly estimate the SCM reactivity by dissolving cement and hydrates while keeping unreacted SCM particles intact [247]. However, the accuracy of this method is limited due to uncertainties in complete dissolution of cement and hydrates or partial dissolution of the SCMs [244,245]. X-ray diffraction and SEM image analysis combined with EDX element mapping are also used to directly measure the SCM reactivity in cement [248-250]. As most of the SCMs are highly amorphous, the quantification of SCMs reactivity from XRD patterns is complicated. Also, the accuracy to quantify the unreacted SCM in cement using SEM image analysis is low. Recently, Nuclear Magnetic Resonance

(^{27} Al

and

^{29} Si

) spectroscopy was shown to directly measure the SCM reactivity in
选择性溶解方法是直接估计 SCM 反应性的最常用方法，通过溶解水泥和水合物，同时保持未反应的 SCM 颗粒完整。然而，由于水泥和水合物的完全溶解或 SCM 的部分溶解存在不确定性，这种方法的准确性受到限制。X 射线衍射和扫描电子显微镜图像分析结合 EDX 元素映射也用于直接测量水泥中的 SCM 反应性。由于大多数 SCM 高度无定形，从 XRD 图谱中量化 SCM 反应性是复杂的。此外，使用 SEM 图像分析量化水泥中未反应 SCM 的准确性较低。最近，核磁共振光谱被证明可以直接测量 SCM 反应性。
cement with good accuracy [251]. These direct testing methods, however, are restricted by time consumption, complexity, and cost.
水泥的准确性良好[251]。然而，这些直接测试方法受到时间消耗、复杂性和成本的限制。

Different testing methods have been employed to assess the SCM reactivity indirectly. Strength activity index is the most commonly used indicator to evaluate the pozzolanic activity of SCMs in blended cements [166,252]. This performance-based test, however, is not considered as an absolute measurement of SCM reactivity due to different effects of physical packing or filling of testing mold. Also, this test method often requires 28 days to evaluate the SCM reactivity. Consumption of Ca

(OH)_{2}

is another commonly used parameter to evaluate the SCM reactivity in cement. Recently, RILEM Technical Committee “Tests on Reactivity of SCMs” proposed a new test method to follow the SCMs reaction process either by isothermal calorimetry heat release and bound water measurements, named as

R^{3}

test [164]. It is currently a standardized test, ASTM C 1897-20. In this test method, a model pastes which includes

{CaCO}_{3}, KOH

and

K_{2} {SO}_{4}

in addition to

Ca (OH)_{2}

is prepared and cured at

40^{\circ} C

to accelerate its reactivity. The SCM reaction progress is followed either by monitoring the heat release by isothermal calorimetry or by measuring the bound water content up to 3-7 days on this prepared

R^{3}

model paste. Both Chapelle/modified Chapelle and Frattini tests that use the

Ca (OH)_{2}

consumption as a proxy for SCM reactivity cannot cover both pozzolanic and latten hydraulic materials [253]. The modified Chapelle test is also standardized in France, NF P18-513:2012.
不同的测试方法已被采用以间接评估 SCM 的反应性。强度活性指数是评估混合水泥中 SCM 火山灰活性的最常用指标[166,252]。然而，由于物理填充或测试模具填充的不同影响，这种基于性能的测试并不被视为 SCM 反应性的绝对测量。此外，这种测试方法通常需要 28 天来评估 SCM 的反应性。Ca

(OH)_{2}

的消耗是评估水泥中 SCM 反应性的另一个常用参数。最近，RILEM 技术委员会“SCM 反应性测试”提出了一种新的测试方法，通过等温量热法的热释放和结合水测量来跟踪 SCM 的反应过程，称为

R^{3}

测试[164]。这目前是一个标准化测试，ASTM C 1897-20。在此测试方法中，准备了一种模型浆料，其中包括

{CaCO}_{3}, KOH

和

K_{2} {SO}_{4}

，以及

Ca (OH)_{2}

，并在

40^{\circ} C

下固化以加速其反应性。 SCM 反应进程可以通过等温热量计监测热释放或通过测量在准备好的

R^{3}

模型浆料中绑定水含量，持续 3-7 天来跟踪。使用

Ca (OH)_{2}

消耗作为 SCM 反应性的代理的 Chapelle/改良 Chapelle 测试和 Frattini 测试无法涵盖火山灰和水硬性材料[253]。改良 Chapelle 测试在法国也已标准化，标准号为 NF P18-513:2012。

In a modification of the

R^{3}

test, the reactivity of different SCMs types were estimated by measuring heat release from isothermal calorimetry and consumption of

Ca (OH)_{2}

on paste, with

3 : 1

mass ratio of

Ca (OH)_{2}

and SCM with solution of potassium hydroxide

(0.5 M)

by maintaining Liquid/Solid ratio of 0.9 [254]. The results show that the reactivity of SCMs mainly depends on its fineness, amorphous content and chemical composition including calcium, alumina and silica content, which is in agreement with previous studies [254]. In addition to the physical and chemical properties of SCMs , the availability of

Ca (OH)_{2}

, water and space controls the SCMs reactivity in cement-SCM paste over time. These mechanisms affecting the SCMs reactivity are well reported in [166].
在对

R^{3}

测试的修改中，通过测量等温热量计的热释放和

Ca (OH)_{2}

在浆料中的消耗，估计了不同 SCM 类型的反应性，

3 : 1

的质量比为

Ca (OH)_{2}

，SCM 与氢氧化钾溶液

(0.5 M)

的液固比保持在 0.9 [254]。结果表明，SCM 的反应性主要取决于其细度、非晶含量和化学成分，包括钙、铝土矿和二氧化硅含量，这与之前的研究一致[254]。除了 SCM 的物理和化学性质外，

Ca (OH)_{2}

、水和空间的可用性在水泥-SCM 浆料中控制了 SCM 的反应性。这些影响 SCM 反应性的机制在[166]中有详细报道。

Ternary cements with two different SCMs have received considerable interest in recent years as it can reduce the clinker by more than

50 %

. However, the order of SCMs reactivity and factors controlling it in ternary cement has not been well-reported. Changing SCM parameters, such as surface area by grinding or better combinations, can help to increase SCM inherent reactivity (e.g., limestone calcined clays). The most suitable strategy can be the activation by counter-anion additions such as carbonates and sulfates to generate reduced solubility hydrates with the goal of enhancing driving power and decreasing the activity of inhibitors such as aluminate species. However, some combination can be counterproductive and the reactivity of some SCMs can retard others. Our understanding of how SCM characteristics affect reactivity in both model systems and real blended cements is important to optimize their use.
近年来，含有两种不同矿物掺合料的三元水泥受到了相当大的关注，因为它可以将熟料减少超过

50 %

。然而，三元水泥中矿物掺合料的反应性顺序及其控制因素尚未得到充分报道。通过研磨改变矿物掺合料的参数，如表面积，或更好的组合，可以帮助提高矿物掺合料的固有反应性（例如，石灰石煅烧粘土）。最合适的策略可能是通过添加反离子，如碳酸盐和硫酸盐，来激活，以生成溶解度降低的水合物，旨在增强驱动力并降低抑制剂（如铝酸盐物种）的活性。然而，一些组合可能适得其反，某些矿物掺合料的反应性可能会抑制其他掺合料。我们对矿物掺合料特性如何影响模型系统和实际混合水泥中反应性的理解，对于优化其使用至关重要。

4.6. Strength vs. ${CO}_{2}$ footprint
4.6. 强度与 ${CO}_{2}$ 足迹

Like the eco-efficiency concept, some attempts have proposed to combine mechanical and environmental performance indicators to assess sustainable solutions using SCMs [47,171]. Material efficiency relies mostly on strength development but recent tools and studies integrate one or more of the following effects: resource depletion and its long-term socio-economic impacts; raw material extraction and its impact on the environment, landscape impact and future recreational purposes; the use of energy in material production processes and the depletion of non-renewable energy sources; harmful emissions from materials manufacturing processes and their local and/or global environmental impacts. Additionally, in most of the cases, material cost due to the limited availability of raw materials or a higher need for energy and/or labor, in the different phases of production processes is not included as this information are not available. The tendency to develop
像生态效率概念一样，一些尝试提出将机械和环境性能指标结合起来，以评估使用 SCM 的可持续解决方案 [47,171]。材料效率主要依赖于强度发展，但最近的工具和研究整合了以下一种或多种影响：资源枯竭及其长期社会经济影响；原材料开采及其对环境的影响、景观影响和未来休闲用途；材料生产过程中的能源使用和不可再生能源的枯竭；材料制造过程中的有害排放及其对当地和/或全球环境的影响。此外，在大多数情况下，由于原材料的有限供应或在不同生产阶段对能源和/或劳动力的更高需求，材料成本并未被纳入，因为这些信息不可用。发展趋势是
more and more composite cements based on calcined clays, limestone and natural pozzolans and since the overall availability of key SCMs is so good, material depletion could be in some calculation ignored in the environmental or sustainability assessment. However, while availability is good, impacts related to land use, energy consumption and/or some emissions are significant [255].
越来越多的复合水泥基于煅烧粘土、石灰石和天然火山灰，并且由于关键的补充材料的整体可用性非常好，材料枯竭在某些计算中可能在环境或可持续性评估中被忽略。然而，尽管可用性良好，但与土地使用、能源消耗和/或某些排放相关的影响是显著的[255]。

There is generally not a scarce resource to produce blended cements. However, some SCMs can be regionally not available or limited in supply. Additionally, due to the amounts used for the production and the transport costs related, even the highly available materials must be localized near the production sites. Viable sources may be limited at the regional and local levels [9,52,256-259]. The precise selection and assessment of factors that make raw materials important or rare are still open research questions. For example, raw materials can be considered essential if they are of national importance to economies and their current or future supply is threatened [260-264]. Other important sources may arise from specific ecological, social or political considerations.
通常没有稀缺资源用于生产混合水泥。然而，一些矿物掺合料在某些地区可能不可用或供应有限。此外，由于生产所需的数量和相关的运输成本，即使是高度可用的材料也必须靠近生产地点进行本地化。可行的资源在区域和地方层面可能有限[9,52,256-259]。确定和评估使原材料重要或稀缺的因素的精确选择仍然是开放的研究问题。例如，如果原材料对经济具有国家重要性，并且其当前或未来的供应受到威胁，则可以认为它们是必不可少的[260-264]。其他重要来源可能源于特定的生态、社会或政治考虑。

The optimized use of the materials has a significant effect on construction profitability. The positive effects on cost and productivity can be seen as a natural driver towards material efficiency in the construction industry. Minimizing material losses (reactive material used as filler, like in the case of several OPC slag cements) directly impacts the costs. On the other hand, it offers greater flexibility and better use of future scarce SCMs in some area (e.g., slag in Europe) and would have a significant impact on lifecycle costs. From technical point of view, the number of useful by-products SCMs is limited and unlikely to increase. However, recent studies have shown that combination with limestone can further increase the rate of clinker replacement while allowing for a relatively low content of by product SCMs in the cement. There is a need for the development of multicomponent cement formulation optimization tool that reduces Portland cement clinker and by-products content while maintaining cement performance.
材料的优化使用对建筑盈利能力有显著影响。成本和生产率的积极影响可以被视为建筑行业材料效率的自然驱动因素。最小化材料损失（如在几种普通波特兰水泥矿渣水泥中使用的反应性材料作为填料）直接影响成本。另一方面，它在某些领域（例如，欧洲的矿渣）提供了更大的灵活性和更好地利用未来稀缺的矿物掺合料，并将对生命周期成本产生重大影响。从技术角度来看，有用的副产品矿物掺合料的数量有限，并且不太可能增加。然而，最近的研究表明，与石灰石的结合可以进一步提高熟料替代率，同时允许水泥中副产品矿物掺合料的相对低含量。需要开发多组分水泥配方优化工具，以减少波特兰水泥熟料和副产品含量，同时保持水泥性能。

Tools should consider the specific interaction between clinker, SCMs and limestone. By understanding the microstructural properties of the system under study, the compressive strength at different hydration times can be predicted and correlated to the

{CO}_{2}

emissions of the binder. Therefore, the effective environmental impact of composite cement can be calculated. Optimized composite cements with

50 wt

cement clinker and below, and

%

limestone besides other SCMs have, on the one hand, significant performance and, on the other hand, the lowest effective

{CO}_{2}

potential.
工具应考虑熟料、矿物掺合料和石灰石之间的具体相互作用。通过了解所研究系统的微观结构特性，可以预测不同水化时间下的抗压强度，并将其与粘合剂的

{CO}_{2}

排放相关联。因此，可以计算复合水泥的有效环境影响。优化的复合水泥具有

50 wt

。

水泥熟料及以下，以及

%

石灰石和其他矿物掺合料，既具有显著的性能，又具有最低的有效

{CO}_{2}

潜力。

4.7. Durability 4.7. 耐久性

In recent years, the research on durability of low

{CO}_{2}

cement system has focused on calcined clay cement [265] though other systems have been investigated such as ternary Portland/slag/limestone system [41,266-268] and binary Portland/limestone systems [41,269-273], standardized in Europe as CEM VI and CEM II C/M respectively for high substitution level [134]. In this section, we focus on calcined clay systems.
近年来，低

{CO}_{2}

水泥系统的耐久性研究主要集中在煅烧粘土水泥[265]，尽管也有研究其他系统，如三元波特兰/矿渣/石灰石系统[41,266-268]和二元波特兰/石灰石系统[41,269-273]，在欧洲分别标准化为 CEM VI 和 CEM II C/M，以实现高替代水平[134]。在本节中，我们重点讨论煅烧粘土系统。

The durability of calcined clay cement has been recently reviewed [265] in terms of chloride ingress, carbonation rate, external sulfate attack (ESA), freeze thaw resistance (FT) and alkali silica reaction (ASR). In the case of external sulfate attack, no thaumasite attack was observed [274,275]. Concerning, freeze thaw, limited studies have been published (see in [265]) but the refinement of porosity along with air entrainment indicate that performance is ensured based on previous experience. Concerning ASR, calcined clay cement can even reduce expansion with respect to a reference concrete [276]. We focus below on the two main deterioration mechanisms of importance to reinforced concrete; chloride and carbon dioxide initiated corrosion of rebars.
最近对煅烧粘土水泥的耐久性进行了评估[265]，涉及氯离子侵入、碳化速率、外部硫酸盐侵袭（ESA）、冻融抗力（FT）和碱-硅反应（ASR）。在外部硫酸盐侵袭的情况下，没有观察到硅铝石侵袭[274,275]。关于冻融，已发表的研究有限（见[265]），但孔隙率的改善以及气泡掺入表明，基于以往经验，性能是有保障的。关于 ASR，煅烧粘土水泥甚至可以减少与参考混凝土相比的膨胀[276]。我们下面重点关注对钢筋混凝土重要的两种主要劣化机制：氯离子和二氧化碳引发的钢筋腐蚀。

The rate of chloride ingress in concrete is governed by two main properties: 1) the chemical (precipitation) or physical (adsorption) binding of chloride in the matrix

[277, 278]

and 2) the effective
混凝土中氯离子渗入的速率受两个主要特性的影响：1）氯离子在基体中的化学（沉淀）或物理（吸附）结合

[277, 278]

，以及 2）有效性
diffusivity of chloride in the concrete matrix [279,280]. On top of concrete recipes and chloride concentration thresholds for corrosion initiation, these former two properties are included in model to assess duration of rebar corrosion initiation [281]. Recent studies have shown that the addition of different pozzolanic additions such as calcined clays or ground glass clays in particular can both increase the chloride binding capacity [282] and lower effective diffusivity [283-285]. Even calcined clays with low metakaolin content below

50 %

seems to be sufficient to achieve good performance at 50% replacement level [286,287]. If there seems to be an optimum chloride binding for

Ca / Al

molar ratio of binder of about 4-6 [282,288] with small variation of binding outside this range, the apparent diffusivity is more influenced by the effective diffusivity that decreases up to two orders of magnitude with respect to reference cements [286]. In addition, nano silica added to improve early strength of calcined clay cement blend (1-2 wt.%) can further refine porosity; increase resistivity and lower effective diffusivity [289]. Finally, the excellent correlation between effective diffusivity and conductivity helps the performance assessment [285]. Traditional pozzolans like fly ash, silica fume, natural pozzolans like pumice, perlite, and lassenite, as well as innovative pozzolans such ground glasses and calcined clays were all the subject of experimental studies. Many of the studied materials show promise as alternatives to fly ash. A trustworthy test to ascertain a pozzolan’s level of reactivity is obviously needed given the considerable range in performance of these materials. According to the findings of Kasaniya et al [290], the material’s pozzolanic reactivity can affect the strength and permeability of concrete. It is also addressed how electrical resistivity can be used to gauge how well pozzolans function when used to partially replace Portland cement in concrete in terms of strength development and resistance to chloride penetration. This suggests that non-calcined natural pozzolans (pumices in this study) can generally be beneficiated by simply grinding the materials finer. The pozzolanic reaction results in a refinement of the concrete pore structure, which includes a reduction in the size and connectivity of the pores and an increase in tortuosity. This is largely responsible for the increased electrical resistance and resistance to chlorides produced by pozzolans. The addition of pozzolans change the chemical composition of the pore solution of the concrete and, consequently, its electrical resistivity, which in turn would affect the concrete’s bulk resistivity. Most of the time, pozzolans will enhance the electrical resistance of the concrete by increasing the cementitious products’ higher alkali binding, which in turn reduces the concentration of ions in the concrete pore solution.
氯离子在混凝土基体中的扩散性[279,280]。除了混凝土配方和腐蚀起始的氯离子浓度阈值，这两个属性也被纳入模型中，以评估钢筋腐蚀起始的持续时间[281]。最近的研究表明，添加不同的火山灰材料，如煅烧粘土或磨碎的玻璃粘土，特别是可以同时增加氯离子的结合能力[282]，并降低有效扩散性[283-285]。即使是低含量的煅烧粘土，低于

50 %

，在 50%的替代水平下似乎也足以实现良好的性能[286,287]。如果在约 4-6 的结合剂摩尔比下，氯离子的结合似乎存在一个最佳值[282,288]，在这个范围之外的结合变化较小，那么表观扩散性更受有效扩散性的影响，后者相对于参考水泥可降低两个数量级[286]。此外，添加纳米二氧化硅以提高煅烧粘土水泥混合物的早期强度（1-2 wt.%）可以进一步细化孔隙率；增加电阻率并降低有效扩散性[289]。最后，有效扩散率与导电性之间的优良相关性有助于性能评估[285]。传统的火山灰如粉煤灰、硅灰、天然火山灰如浮石、珍珠岩和拉森石，以及创新的火山灰如磨碎的玻璃和煅烧粘土，都是实验研究的对象。许多研究材料显示出作为粉煤灰替代品的潜力。鉴于这些材料性能的显著差异，显然需要一个可靠的测试来确定火山灰的反应性水平。根据 Kasaniya 等人的研究结果[290]，材料的火山灰反应性可以影响混凝土的强度和渗透性。还讨论了如何利用电阻率来评估火山灰在混凝土中部分替代波特兰水泥时在强度发展和抗氯离子渗透方面的表现。这表明，非煅烧的天然火山灰（本研究中的浮石）通常可以通过简单地将材料磨得更细来提高其性能。火山灰反应导致混凝土孔隙结构的精细化，包括孔隙大小和连通性的减少以及曲折度的增加。这在很大程度上是火山灰所产生的电阻和抗氯离子的增加的主要原因。火山灰的添加改变了混凝土孔隙溶液的化学成分，因此也改变了其电阻率，这反过来会影响混凝土的体积电阻率。大多数情况下，火山灰通过增加水泥产品的高碱结合来增强混凝土的电阻，从而减少混凝土孔隙溶液中离子的浓度。

The carbonation process is governed by the calcium buffering capacity of cement and

{CO}_{2}

diffusivity of concrete [291]. In 2015, Leemann et al. [292] showed 1) the correlation between carbonation rate and the initial water to reactive CaO ratio and 2) a good correlation between accelerated and natural carbonation rate at constant RH. In addition, both climate and concrete curing influence carbonation rate by modifying the

{CO}_{2}

diffusivity. The effect of curing on carbonation rate is significant: up to factor 2 to 3 increase of rate with a reduction of curing from 28 d to 1 d in natural conditions. The data on curing are rather scattered: some authors suggests that this curing factor could be binder specific [293] while other do not [294] (Fig. 7a). Calcined clay cement concrete [295] or other SCM [293] show similar behavior: they follow the same trend as the one highlighted by Leemann [292]. Reacted CaO , reactive CaO (defined in [292]) or maximum

{CO}_{2}

binding capacity (MBC, defined in [296]) can be used as used as indicator with the same quality of correlation [295] (Fig. 7b). One could have imagined much better performance of pozzolanic cement such as calcined clay or slag cement because of the porosity refinement with respect to pure Portland cement. However, upon carbonation, a change of microstructure occurs without loss of compressive strength: while the total water or MIP porosity is often decreasing, the pore entry radius of carbonated matrices is increasing [296,297] leading to a lower sorption capacity and an increase of

{CO}_{2}

diffusivity [296] or an increase of gas permeability and water sorptivity [298]. From the engineering point of view,
碳化过程受水泥的钙缓冲能力和混凝土的扩散性控制[291]。2015 年，Leemann 等人[292]显示了 1) 碳化速率与初始水与反应性 CaO 比率之间的相关性，以及 2) 在恒定相对湿度下加速碳化速率与自然碳化速率之间的良好相关性。此外，气候和混凝土养护通过改变扩散性影响碳化速率。养护对碳化速率的影响显著：在自然条件下，养护时间从 28 天减少到 1 天，碳化速率可增加 2 到 3 倍。关于养护的数据相当分散：一些作者建议这个养护因素可能是特定于粘合剂的[293]，而其他作者则不同意[294]（图 7a）。煅烧粘土水泥混凝土[295]或其他矿物掺合料[293]表现出类似的行为：它们遵循与 Leemann[292]强调的相同趋势。反应性 CaO、反应性 CaO（在[292]中定义）或最大结合能力（MBC，在[296]中定义）可以作为具有相同相关性质量的指标[295]（图 7b）。人们本可以想象，火山灰水泥如煅烧粘土或矿渣水泥的性能会比纯波特兰水泥更好，因为其孔隙率得到了改善。然而，在碳化过程中，微观结构发生变化，但压缩强度并未降低：虽然总水分或 MIP 孔隙率通常在下降，但碳化基体的孔入口半径却在增加[296,297]，这导致吸附能力降低以及扩散性增加[296]，或气体渗透性和水分吸附性增加[298]。从工程的角度来看，
low

{CO}_{2}

cement and concrete can be designed to meet service life in carbonation exposure class [299].
低

{CO}_{2}

水泥和混凝土可以设计以满足碳化暴露等级 [299] 的使用寿命。

For both Cl - and

{CO}_{2}

exposure classes, despite the performance of low

{CO}_{2}

cement, some studies highlighted the corrosion rate of rebars after initiation, i.e., during the corrosion propagation phase. For example Nguyen [300] showed the similar behavior of calcined clay cement vs. OPC in presence of wetting drying cycles. The decrease of pH upon carbonation at the steel concrete interface is a necessary but not sufficient condition for rebar corrosion; moisture activity at the steel, carbonated concrete interface is also key [301]. Recent results on carbonated cement mortar shows that rebar corrosion rates are under anodic control and are a monotonic function of relative humidity [302], confirming past experience [303]. Thus similarly to the corrosion weathering of steel, the time of wetness at the steel concrete interface should be a critical factor [304]. Early results on rebar corrosion in calcined clay systems have been published [305]. However, the corrosion rate of rebar in low

{CO}_{2}

cement and concrete should be further assessed as a function of environment and time of wetness.
对于 Cl -和

{CO}_{2}

暴露类别，尽管低

{CO}_{2}

水泥的性能，一些研究强调了钢筋在腐蚀启动后，即在腐蚀扩展阶段的腐蚀速率。例如，Nguyen [300]展示了在湿干循环存在下，煅烧粘土水泥与普通波特兰水泥的类似行为。钢筋混凝土界面在碳化过程中 pH 值的降低是钢筋腐蚀的必要但不充分条件；钢筋与碳化混凝土界面的湿度活动也是关键因素[301]。关于碳化水泥砂浆的最新结果表明，钢筋腐蚀速率受阳极控制，并且是相对湿度的单调函数[302]，确认了过去的经验[303]。因此，与钢材的腐蚀风化类似，钢筋混凝土界面的湿润时间应是一个关键因素[304]。关于煅烧粘土体系中钢筋腐蚀的早期结果已被发布[305]。然而，低

{CO}_{2}

水泥和混凝土中钢筋的腐蚀速率应进一步评估，作为环境和湿润时间的函数。

4.8. Calculation of optimum composition
4.8. 最优成分的计算

The problem of rational material selection is a classic materials Science problem [306] which can be mathematically reformulated as a problem of optimization under constraints. The quantities to optimize are strength, rheology, durability, and most importantly for cement manufacturers, cost (which, in Europe, includes the

{CO}_{2}

price through carbon certificates). The constraints vary with the geographical area, raw materials and technologies availability vary from place to place, as well as standards.
合理材料选择的问题是一个经典的材料科学问题[306]，可以数学上重新表述为一个约束下的优化问题。需要优化的量包括强度、流变性、耐久性，以及对水泥制造商来说最重要的成本（在欧洲，这包括通过碳证书的

{CO}_{2}

价格）。约束条件因地理区域而异，原材料和技术的可用性因地而异，标准也各不相同。

The optimization of cement and concrete properties depends on many variables. Cement strength depends on the cement mineralogy

(C_{3} S, C_{2} S, C_{3} A

and alkali content), cement fineness, water amount and SCM reactivity. SCM reactivity depends at least on fineness, and reactivity of the constituents, as minerals and glasses. The rheology of fresh concrete depends on many interacting variables as Fig. 6 shows. The addition of any usual SCM does not lead to any systematic gain or loss of yield stress or viscosity because of the variabilities of the properties of SCM and their interactions with the cement particle packing behavior and mineralogy (with the sulphate and alkali contents).
水泥和混凝土性能的优化依赖于许多变量。水泥强度取决于水泥矿物组成（如矿物学和碱含量）、水泥细度、水的用量和矿物掺合料（SCM）的反应性。矿物掺合料的反应性至少取决于细度以及成分的反应性，如矿物和玻璃。新鲜混凝土的流变性依赖于许多相互作用的变量，如图 6 所示。任何常见的矿物掺合料的添加并不会导致屈服应力或粘度的系统性增益或损失，因为矿物掺合料的性质及其与水泥颗粒堆积行为和矿物组成（包括硫酸盐和碱含量）的相互作用存在变异性。

Consequently, the strength and workability of a ternary Portland systems depends on no less than 12 possibly interacting variables. Common optimization approaches fail to meet the complexity of the situation. Parametric studies require too expensive a budget: with only two levels per variable,

2^{12} = 4096

experiments would be required. Mathematical techniques, like fractional design of experiment, are therefore required to bring the experimental budget down to an affordable cost and time.
因此，三元波特兰水泥系统的强度和可加工性依赖于不少于 12 个可能相互作用的变量。常见的优化方法无法满足这种复杂性。参数研究需要的预算过于昂贵：每个变量只有两个水平时，需要进行

2^{12} = 4096

次实验。因此，需要数学技术，如分数实验设计，以将实验预算降低到可承受的成本和时间。

Models are often categorized as empirical, or mechanistic (alternatively ,pphysics-based"). Empirical models are black boxes that directly predict the performance from the mix design variables whereas mechanistic models predict and explain the performance by relating it to key microstructural features. An empirical model for low clinker mortar strength may directly regress the strength from the mass of each mix constituents, whereas a mechanistic model (like micro mechanical models) may predict the strength as a function of the phase assemblage, phases shapes and pore size distribution, all microstructural features.
模型通常被分类为经验模型或机械模型（也称为“基于物理的”）。经验模型是黑箱，直接根据混合设计变量预测性能，而机械模型则通过将性能与关键微观结构特征相关联来预测和解释性能。低熟料砂浆强度的经验模型可能直接根据每种混合成分的质量回归强度，而机械模型（如微观机械模型）则可能将强度预测为相组装、相形状和孔径分布等微观结构特征的函数。

Whether it be for strength, rheology, or durability performance, most of the existing empirical models have targeted concrete rather than
无论是针对强度、流变性还是耐久性性能，大多数现有的经验模型都针对混凝土，而不是

Fig. 6. Effect of limestone, silica fume, slag and fly ashes on the rheological properties of fresh concrete (figure reproduced from [184] with permission). Because of the variability of the SCM properties and/or interactions of the SCM with the cements (through the overall powder packing density for instance), no systematic trend on the rheological properties is found.
图 6. 石灰石、硅灰、矿渣和粉煤灰对新鲜混凝土流变性质的影响（图源自[184]，已获许可）。由于 SCM 性质的变异性和/或 SCM 与水泥的相互作用（例如通过整体粉末堆积密度），未发现流变性质的系统趋势。

Fig. 7. a) Natural carbonation depth data for different concrete 28 curing vs. 1 day curing [294], b) correlation between accelerated carbonation rate and W/MBC ratio including calcined clay cement (OPC+Q) [295]. (“Figures reproduced from [294 and 295] with permission”).
图 7. a) 不同混凝土 28 天养护与 1 天养护的自然碳化深度数据[294]，b) 加速碳化速率与 W/MBC 比率的相关性，包括煅烧粘土水泥（OPC+Q）[295]。（“图表经[294 和 295]许可转载”）。
cement properties [307], and they have mostly targeted mixes currently allowed on the market, that are by definition high-clinker systems.
水泥性质[307]，他们主要针对目前市场上允许的混合物，这些混合物按定义是高熟料系统。

The predictors for the SCMs reactivity to use as input variables in the models are still a matter of research. Skibsted and Snellings have reviewed in [166] the variables that affect SCMs reactivity. Rather than using the exhaustive mineralogy analysis of the SCM, which would increase dramatically the number of input variables and therefore required dataset size, a pragmatic approach could be to consider a set of predictors derived from accelerated tests like the

R^{3}

test [308].
SCM 反应性的预测因子作为模型中的输入变量仍然是研究的课题。Skibsted 和 Snellings 在[166]中回顾了影响 SCM 反应性的变量。与其使用详尽的 SCM 矿物学分析，这将大幅增加输入变量的数量，从而需要更大的数据集，务实的方法可以考虑从加速测试中得出的预测因子，例如

R^{3}

测试[308]。

The modeling of the durability properties of concrete is an area with many challenging problems. Alexander [309] has emphasized the critical need to consider adequate input variables. The exposure classes, coupling of environmental attacks, effect of loading and crack opening have been barely studied and are not considered by durability and transport models though their critical influence is known.
混凝土耐久性特性的建模是一个面临许多挑战性问题的领域。亚历山大[309]强调了考虑足够输入变量的关键需求。暴露类别、环境侵蚀的耦合、荷载的影响和裂缝开启几乎没有被研究，并且耐久性和传输模型并未考虑这些因素，尽管它们的关键影响是众所周知的。

Micromechanical models have been successfully applied to the prediction of pastes and mortars strength [84]. However, micromechanical models need as input a hydration kinetics model, where progress is in our opinion needed. Much effort has been made on modeling alite hydration [310-319], but less on Portland cement [320-323]. Regarding blended cements, there is yet no existing model that incorporates measured SCM reactivities.
微观机械模型已成功应用于预测浆料和砂浆的强度[84]。然而，微观机械模型需要一个水化动力学模型作为输入，我们认为在这方面仍需进展。虽然在建模铝酸盐水化方面已做了大量工作[310-319]，但在波特兰水泥方面的研究较少[320-323]。关于混合水泥，目前尚无现有模型能够结合测量的矿物掺合料反应性。

Pure PC hydration models, without any SCM, still need progress. Most existing models suffer from shortcomings addressed in details in [232]. Famous models like the Parrott and Killoh model, Hymostruc or mic rely on outdated hypotheses and inadequate geometrical description of the microstructure. In these models, the main hydration peak and later age are assumed to be caused either by a C-S-H diffusion barrier or by C-S-H impingement. Both of these hypotheses are now known to be incorrect [232].
纯粹的 PC 水合模型，没有任何 SCM，仍然需要改进。大多数现有模型存在缺陷，已在[232]中详细讨论。著名的模型如 Parrott 和 Killoh 模型、Hymostruc 或 mic 依赖于过时的假设和不充分的微观结构几何描述。在这些模型中，主要的水合峰和后期年龄被假定是由 C-S-H 扩散屏障或 C-S-H 冲击引起的。这两种假设现在已知是错误的[232]。

Models for blended cements, whether with high or low clinker ratio are missing, but particularly challenging. As reviewed in [166] regarding hydration, the variables that affect SCMs reactivity include the evolution of the pore solution chemistry. The interplay between dissolution and precipitation through the pore solution therefore needs to be modeled. Both the dissolution and precipitation of minerals are unfortunately complicated phenomena. The dissolution of minerals involve surface phenomena such as leaching, (de)protonation, step retreat, etch pits openings as reviewed in [324]. The precipitation mechanism of C-S-H does not occur in one single step but at least two, and only one attempt has been made in the context of synthetic C-S-H
混合水泥的模型，无论是高熟料比还是低熟料比，都缺失，但特别具有挑战性。如[166]中所述，影响矿物掺合料（SCMs）反应性的变量包括孔隙溶液化学成分的演变。因此，必须对通过孔隙溶液的溶解和沉淀之间的相互作用进行建模。不幸的是，矿物的溶解和沉淀是复杂的现象。矿物的溶解涉及表面现象，如浸出、（去）质子化、台阶退缩、蚀刻坑的形成，如[324]中所述。C-S-H 的沉淀机制并不是在一个单一步骤中发生，而是至少需要两个步骤，并且在合成 C-S-H 的背景下仅进行过一次尝试。
precipitation [325]. The effort could therefore be more pragmatic in a first step and consider a set of predictors derived from accelerated tests like the

R^{3}

test [308]. Regarding, rheology, the prediction is no easier as Fig. 6 shows. Since the end of the 2000s, a class of empirical models, socalled machine learning (ML) models and in particular artificial neural networks (ANN) have resurfaced thanks to major breakthroughs on ,niche applications like image and video classification, speech and text recognition" [326]. In the field of concrete science, no less than 389 ML applications have been published as reviewed by Li et al [327]. The enthusiasm in ML learning is certainly understandable given its success in other fields, but the emphasis should not only lie on using the latest ML technique nor simply building large datasets by merging different sources. Rather, the emphasis should also lie on building quality datasets targeted at low clinker systems.
降水[325]。因此，第一步的努力可以更务实，考虑一组来自加速测试的预测因子，如

R^{3}

测试[308]。关于流变学，预测并不容易，如图 6 所示。自 2000 年代末以来，一类经验模型，即所谓的机器学习（ML）模型，特别是人工神经网络（ANN），由于在图像和视频分类、语音和文本识别等小众应用上的重大突破而重新出现[326]。在混凝土科学领域，已有不少于 389 个机器学习应用被发表，正如 Li 等人所回顾的[327]。考虑到机器学习在其他领域的成功，机器学习的热情无疑是可以理解的，但重点不应仅仅放在使用最新的机器学习技术或通过合并不同来源构建大型数据集上。相反，重点还应放在构建针对低熟料系统的高质量数据集上。

5. Knowledge gaps 5. 知识差距

Future optimized clinker studies should aim to gather information about the best firing process and simulate it as closely as possible on a laboratory scale to understand the interconnection between clinker production conditions and compositions and composite cement performance like rheology, interaction with performance enhancers and reactivity to maximize substitution. Future research on clinker quality should potentially rely on machine learning (ML) tools, which are an intriguing avenue of research that may help to understand how reactivity is related to the process, with the goal of controlling it through data modeling [328]. Although the last technology is rather broad, we believe it is a discipline that could use data from industrial processes to improve this over time. In general, ML may help predict the impact of clinkering and cooling conditions on clinker reactivity and to improve the clinker consistency.
未来优化熟料的研究应旨在收集有关最佳烧成工艺的信息，并尽可能在实验室规模上进行模拟，以理解熟料生产条件与成分以及复合水泥性能（如流变性、与性能增强剂的相互作用和反应性）之间的相互关系，以最大化替代。未来对熟料质量的研究可能依赖于机器学习（ML）工具，这是一条引人入胜的研究途径，可能有助于理解反应性与工艺之间的关系，目标是通过数据建模进行控制。尽管这一技术相对广泛，但我们相信这是一个可以利用工业过程数据来逐步改进的学科。一般来说，机器学习可能有助于预测熟料化和冷却条件对熟料反应性的影响，并改善熟料的一致性。

In OPC and Portland Limestone Cement (PLC), the exact relationship between the clinker reactivity and the strength of cement is understood. When using other SCMs, this relationship is different. This needs to be investigated further. The transformation of the tricalcium silicate lattice, the introduction and role of foreign ions in the lattice, and the rate of cooling all require further investigation. Firing cement clinker produces a melt that contains almost all the alumina and iron oxide present in the original crude flour, in addition to CaO . The CaO content of the melt is insufficient to allow complete crystallization of tricalcium aluminate and aluminate ferrite. The thermodynamic relationship between slow
在 OPC 和波特兰石灰石水泥（PLC）中，熟料反应性与水泥强度之间的确切关系是明确的。当使用其他矿物掺合料时，这种关系则有所不同。这需要进一步研究。三钙硅酸晶格的转变、外来离子在晶格中的引入和作用以及冷却速率都需要进一步调查。烧制水泥熟料会产生一种熔体，除了 CaO 外，还含有几乎所有原料粉中存在的铝土矿和铁氧化物。熔体中的 CaO 含量不足以允许三钙铝酸盐和铝酸铁的完全结晶。慢速的热力学关系
cooling and the removal of CaO from

C_{3} S

to form

C_{2} S

is not well understood. More work could be done using pure phases and/or MD simulations. Lowering the formation of

C_{2} S

in the case of pozzolanic cement is crucial to obtain the best performances. A better understanding of the previous relationship is mandatory for future advances.
冷却和从

C_{3} S

中去除 CaO 以形成

C_{2} S

的过程尚不清楚。可以通过使用纯相和/或分子动力学模拟进行更多研究。在火山灰水泥的情况下，降低

C_{2} S

的形成对于获得最佳性能至关重要。对前述关系的更好理解是未来进展的必要条件。

In addition to the advances on clinker optimized reactivity, focus should be given as to develop faster characterization techniques to assess the reactivity of SCMs, particularly in the context of controlling the quality of SCM during production (e.g., calcined clays) or extraction (e.g., pozzolans, fly ashes, etc.). Additionally, a better understanding of the effect of sulfate alumino-silicate alkali balance in the context of hydration of composite cement can help to better optimize the chemistry of the clinker with respect to the SCMs that will be used (avoid high belite content in combination with SCMs used is known for example to suppress its reaction). Increasing the early strength by understanding the limitations of C-S-H growth and the impact of alkalis on early and late limits and performance will help to engineer the right performance enhancer depending on the clinker and SCM in use. Additionally, comparable to the research done on slag cements, blending techniques to optimize the particle size distributions of various other types of SCMs, especially calcined clays and natural pozzolans should be developed. This would help to extend the range of materials and increase the level of substitution by maintaining or improving early age strengths of these blended binders. This can potentially help in the development of more robust mix-design methodologies for concrete with low cement or paste content.
除了对熟料优化反应性的进展外，还应关注开发更快速的表征技术，以评估矿物掺合料（SCMs）的反应性，特别是在控制生产（例如，煅烧粘土）或提取（例如，火山灰、粉煤灰等）过程中 SCM 的质量方面。此外，更好地理解硫酸铝硅酸盐碱平衡在复合水泥水化过程中的影响，可以帮助更好地优化熟料的化学成分，以适应将要使用的 SCM（例如，避免与已知会抑制其反应的 SCM 组合时高贝利特含量）。通过理解 C-S-H 生长的限制以及碱对早期和晚期极限及性能的影响来提高早期强度，将有助于根据所使用的熟料和 SCM 设计合适的性能增强剂。此外，类似于对矿渣水泥的研究，应开发混合技术，以优化各种其他类型 SCM 的颗粒大小分布，特别是煅烧粘土和天然火山灰。这将有助于扩展材料的范围，并通过保持或提高这些混合粘合剂的早期强度来增加替代水平。这可能有助于开发更强健的混合设计方法，适用于低水泥或浆料含量的混凝土。

More broadly, it is critical to further characterize the hydration process and the potential interactions that additives, performance enhancers and minors’ additions may have on various processes such as dissolution, nucleation, and growth. This is an important area of research that needs to be pursued, not only because new blends of SCMs with possibly higher substitution levels will be introduced in the coming years but also because this would help to find ways to increase the early age strength of low

{CO}_{2}

cements without affecting workability or late strength evolution.
更广泛地说，进一步表征水合过程以及添加剂、性能增强剂和微量添加物可能对溶解、成核和生长等各种过程的潜在影响是至关重要的。这是一个需要深入研究的重要领域，不仅因为在未来几年将引入可能具有更高替代水平的新型 SCM 混合物，还因为这将有助于寻找在不影响可加工性或后期强度演变的情况下提高低

{CO}_{2}

水泥早期强度的方法。

Concerning durability, we need to understand the link between clinker content of cement and concrete and the good service life of structure. We need to know how to quickly measure carbonation rates in ways that simulates the real conditions. The only test currently accepted throughout Europe is to measure the carbonation rate for concrete stored at 60% RH with atmospheric carbonation levels, which takes at least a year. Other measurements, ideally non-destructive, and ageing methods are needed. Additionally, we need to understand the role of curing and water-to-cement ratio on the capacity of low carbon concrete to absorb

{CO}_{2}

. There is a need to better understand how the carbonation resistance in low carbon concrete evolves over the lifetime of structures in real climatic conditions, and how it is affected by process parameters such as w/c, curing, and surface treatments. Another, perhaps more important question that has received much less attention up to now is whether steel in carbonated concrete will corrode in real-world situations knowing that recent advances insights have shown that the internal relative humidity of concrete is the most critical parameter. High RH coupled to carbonation is uncommon in concrete with a reasonable cover depth. More research is needed to accurately identify the situations in which active corrosion due to carbonation is likely to occur and those in which it is extremely unlikely, and to define corrosion indicator such as time of wetness based on climate and material properties.
关于耐久性，我们需要理解水泥和混凝土的熟料含量与结构良好使用寿命之间的联系。我们需要知道如何快速测量碳化速率，以模拟真实条件。目前在欧洲唯一被接受的测试是测量在 60%相对湿度和大气碳化水平下储存的混凝土的碳化速率，这需要至少一年。还需要其他测量，理想情况下是无损的，以及老化方法。此外，我们需要理解养护和水灰比对低碳混凝土吸收

{CO}_{2}

能力的影响。还需要更好地理解低碳混凝土在真实气候条件下结构使用寿命中碳化抗力的演变，以及它如何受到如水灰比、养护和表面处理等工艺参数的影响。另一个或许更重要的问题是，碳化混凝土中的钢材在现实情况下是否会腐蚀，考虑到最近的研究进展表明混凝土内部相对湿度是最关键的参数。高相对湿度与碳化结合在具有合理保护层深度的混凝土中并不常见。需要更多研究来准确识别由于碳化而导致主动腐蚀可能发生的情况以及极不可能发生的情况，并根据气候和材料特性定义腐蚀指标，如湿润时间。

While blended cements as described previously can contain more calcium aluminate and AFm phases (monosulfate, mono or hemi carbonate), which can immobilize chloride by forming Friedel’s salt, they also contain less C-S-H due to the lower amount of clinker. Additionally, a decrease in pore solution pH is observed in most of the blended cements, which is understandable given that there are fewer alkalis (

Na +

K +

) to counterbalance the incoming negative chloride ions. Nevertheless, the performance of blended systems with respect to chloride surpasses the OPC one. Other additional factors related to ion movement
混合水泥如前所述可以含有更多的铝酸钙和 AFm 相（单硫酸盐、单碳酸盐或半碳酸盐），这些相可以通过形成弗里德尔盐来固定氯离子，但由于熟料含量较低，它们也含有较少的 C-S-H。此外，在大多数混合水泥中观察到孔溶液 pH 值的降低，这是可以理解的，因为可用的碱性物质较少（

Na +

，

K +

），无法抵消进入的负氯离子。然而，混合体系在氯离子方面的表现超过了普通波特兰水泥。与离子运动相关的其他附加因素。
near charged surfaces could be the trigger for it. The pore structure of concrete is dominated by interhydrate pores, which are narrow channels around 10 nm in size between the C-S-H hydrates. It is obvious that better understanding ion transport in small pores is critical to better understand chloride ingress.
靠近带电表面的区域可能是其触发因素。混凝土的孔隙结构主要由水合物孔隙主导，这些孔隙是 C-S-H 水合物之间约 10 纳米大小的狭窄通道。显然，更好地理解小孔隙中的离子传输对于更好地理解氯离子的渗入至关重要。

All SCMs unless they contain free alkali (fly ash, slag, calcined clay, silica fume, etc.) are effective at reducing the risk of deleterious expansion due to alkali silica reaction, just as they are with chloride ingress. The primary issue and research need here is to have a reliable test method to determine the amount of a specific SCM in the blend required to suppress alkali silica reaction (ASR) for a specific aggregate.
所有的 SCM，除非它们含有游离碱（如粉煤灰、矿渣、煅烧粘土、硅灰等），否则在减少由于碱-硅反应引起的有害膨胀风险方面是有效的，就像它们对氯离子侵入的作用一样。这里的主要问题和研究需求是拥有一种可靠的测试方法，以确定在特定骨料中抑制碱-硅反应（ASR）所需的特定 SCM 的混合量。

Two main levers would contribute to accelerating the deployment of new standards and in reducing the time to market for new products. First, despite many scientific studies, the transfer of knowledge into published standards is sometimes limited. This aspect could be significantly improved by conducting the research works in a more adapted way corresponding to expectations from standardization bodies. This implies for instance the use of standardized testing methods or compliance with guidelines (CEN/TR 16912:2016 for instance [329]) to prepare technical dossiers in order to facilitate the submission of a request. A second improvement lies in the implementation of new cement standards into application standards such as concretes and mortars standards. Procedures are often very long, and this can be explained by different local practices in design rules, concrete or mortar mix design and execution. More harmonization would facilitate the deployment of new products.
两个主要杠杆将有助于加速新标准的实施，并缩短新产品的上市时间。首先，尽管有许多科学研究，但知识转化为已发布标准的过程有时是有限的。通过以更符合标准化机构期望的方式进行研究工作，这一方面可以显著改善。例如，这意味着使用标准化的测试方法或遵循指南（例如 CEN/TR 16912:2016）来准备技术文件，以便于提交请求。第二个改进在于将新的水泥标准实施到应用标准中，例如混凝土和砂浆标准。程序通常非常漫长，这可以通过设计规则、混凝土或砂浆配合设计和执行中的不同地方实践来解释。更多的协调将有助于新产品的推广。

Declaration of competing interest
竞争利益声明

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
作者声明，他们没有已知的竞争性财务利益或个人关系，这些关系可能会影响本文所报告的工作。

Data availability 数据可用性

No data was used for the research described in the article.
文章中描述的研究没有使用任何数据。

Acknowledgements 致谢

We would like to thank everyone who shared valuable information regarding the content of this article: Rémi Barbarulo, Xavier Guillot, Doug Hooton, Peter Kruspan, Christophe Levy, Bian Wang, Maciej Zajac, Gerd Bolte, Yosra Briki and Arnaud Muller.
我们要感谢所有分享有关本文内容的宝贵信息的人：Rémi Barbarulo、Xavier Guillot、Doug Hooton、Peter Kruspan、Christophe Levy、Bian Wang、Maciej Zajac、Gerd Bolte、Yosra Briki 和 Arnaud Muller。

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- Corresponding author. 通讯作者。
E-mail address: mohsen.ben.haha@heidelbergmaterials.com (M. Ben Haha).
电子邮件地址：mohsen.ben.haha@heidelbergmaterials.com (M. Ben Haha)。

Low clinker systems - Towards a rational use of SCMs for optimal performance 低熟料系统 - 朝着合理使用矿物掺合料以实现最佳性能的方向

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