A B S T R A C T 随着氧化铝产量的增长,人们对赤泥这种高碱性、高危险性的工业废弃物的关注度也越来越高。本研究试图通过用赤泥和其他固体废弃物替代传统水泥,降低能源消耗和环境污染,促进废弃物的资源化利用。该研究采用单纯形向心法,利用赤泥 (RM)、钢渣 (SS)、粉煤灰 (FA) 和磷石膏 (PG),提出了一种新的固体废弃物胶凝材料设计方案,命名为 RSF +P 系列,将赤泥转化为生态友好型工程材料。该研究包括混合物设计、数据分析、TG-DTG、XRD、FTIR、SEM-EDX 等多种测试方法,以及污染物浸出对复合材料环境影响的评估。实验结果表明,RSF +P 系列具有良好的品质,包括合适的凝结时间(初凝时间:188 分钟,终凝时间:437 分钟)、较高的 28d UCS(11.89 兆帕)和较低的渗透性 。)电子平衡分析表明,与传统水泥相比,RSF +P 的制备和应用可减少 一次能源需求和 环境负荷。这项研究对于解决赤泥处置和环境污染问题至关重要,为利用类似废物提供了新的见解。
微颗粒周围的硅酸盐水合物。这些水合物吸附并凝固 Na 和 K 等可溶性碱离子 [13]。在外部压力和温度的作用下,赤泥会硬化,形成结晶网络结构,从而提供强度,并产生坚固的半刚性板,形成坚固的空间网络[9]。这一过程将有害的赤泥转化为环保、可靠的工程填料,适用于建筑工程,实现了赤泥的低成本、大规模利用,有效解决了赤泥大量堆积的问题[2]。
图 5 显示了基于 系统的全固体废弃物胶凝材料组分比设计方法。该方法结合了纯中心设计概念和胶凝材料的工作机理,适用于反应活性不同的胶凝材料。该设计方法根据胶凝材料的反应活性,分为三元(活性剂与高和低反应活性的胶凝材料)和二元(活性剂与单一胶凝材料)胶凝材料设计。配比分为 I、II 和 III 区,分别对应胶凝材料的高性能、中性能和低性能。在区域 I 中,材料的活化剂与胶凝材料充分反应。在区域 II 中,材料中活化剂的含量可能导致性能不佳。在区域 III 中,材料中的活化剂含量过多或不足,使其不适合用作胶凝材料。
当 RM 含量为 时,SS 含量从 增加到 时,初凝时间缩短到 112 分钟,终凝时间从 420 分钟缩短到 170 分钟。无论 RM 含量是 还是 ,SS 含量的增加都会缩短初凝和终凝时间。这与 SS 的高水胶反应活性有关,其玻璃相中的 Ca 和 Al 等元素在碱性环境中会迅速溶解,促进碱活化产物的形成。因此,SS 含量越高,凝结时间越短[22]。
FA 对凝固过程的影响很小,但它会大大延迟碱激活反应的进程。随着 FA 含量的增加,初凝和终凝时间都会明显延长。这是由于 FA 中的 含量高,反应活性低,几乎不参与碱活化反应,导致凝固时间延长。这一结果与 Hidayati 等人的研究结果一致[8]。
4.2.硬化状态特性
4.2.1.渗透系数
在 RSF 三元固体废物系统中,RM、SS 和 FA 混合比例的变化会影响渗透系数。RM 的粒径较大,可能会产生较大的孔隙或通道供水渗透,而其水化活性不足可能无法充分填充这些空隙,从而导致渗透系数增大。相反,SS 和 FA 的颗粒较小,有助于填充孔隙,减少水的渗透,降低渗透系数,从而提高复合材料的密实度。SS 和 FA 更有可能生成水合产物,如水合硅酸钙和水合硅酸铝,这有助于进一步降低渗透性。不过,值得注意的是,与 SS 相比,FA 的反应活性较低,可能需要更高的比例才能达到类似的效果。
4.2.2.非收缩抗压强度
如图 13 所示,RSF 胶凝材料浆体的 UCS 受 RM 和 SS 相对含量的显著影响。RM 含量的增加会降低浆体的早期强度,这是由于过量的 RM 会降低早期强度。相反,SS 含量的增加会提高浆体的强度,因为 SS 具有较高的热固性反应活性。
图 12.RSF 胶凝材料浆料的渗透系数等值线图。
在 RM 提供的碱性环境中,SS 会迅速引发碱激活反应,从而随着 SS 含量的增加而提高浆料的强度。含有 FA 的浆料的强度增长并不显著;FA 含量的增长方向几乎垂直于强度增长等值线。这可能是由于 FA 玻璃相的反应活性较低,几乎不参与早期的碱激活反应,这与凝结时间随 FA 含量增加而延长的趋势一致。
随着固化龄期增加到 28 d 和 90 d,浆料强度受到 RM、SS 和 FA 相对含量的显著影响。RM 含量的增加会逐渐降低浆料强度,最佳的 RM 含量范围在 和 之间。随着 SS 含量的增加,强度增长相对缓慢,这与 SS 的高反应活性有关,它主要参与早期碱活化反应。
(1) RSF 复合材料的固化时间受成分碱度和玻璃状矿物溶解的影响。初凝时间超过 45 分钟,终凝时间低于 600 分钟。与 FA 相比,RM 和 SS 对凝固时间的影响更大,含量越高,初凝和终凝时间都会缩短。
(2) 在三元固体废物系统中,RM、SS 和 FA 含量的变化对透水性的影响不同。RM 的颗粒较大,会产生较大的孔隙,从而增加透水性。相反,SS 和 FA 具有较高的水合潜力,可填充这些孔隙,从而降低渗透性。不过,与 SS 相比,FA 的反应活性较低,这意味着可能需要更多的 FA 才能产生类似的效果。
(3) 胶浆强度取决于组分比例。增加 RM 可提高初期强度,但超过 60-70% 的最佳范围后强度会降低。较高的 SS 可提高早期强度,而较多的 FA 会降低早期强度,但后期强度会提高。PG 可改善机械性能。最佳 RM:SS:FA:PG 比率为 5.4:0.9:2.7:1,90 d UCS 为 13.94 MPa。多项式模型 (90dUCS) 的调整 为 0.8983,具有显著的统计学意义,方差分析结果也证实了这一点。
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