Tea stain-inspired treatment for fine recycled concrete aggregates
Tea stain-inspired treatment for fine recycled concrete aggregates
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DOI：
10.1016/j.conbuildmat.2020.120027
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发表时间：
2020-11
影响因子：
7.4
通讯作者：
Liang Wang;Jialai Wang;Xin Qian;Yi Fang;Peiyuan Chen;Atolo Tuinukuafe
中科院分区：
文献类型：
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作者：
Liang Wang;Jialai Wang;Xin Qian;Yi Fang;Peiyuan Chen;Atolo Tuinukuafe
再生混凝土骨料中有很大一部分是细骨料。一旦在新混凝土中回收，细RCA可显著降低混凝土的机械强度和耐久性，因为细RCA具有高吸水性和高孔隙率。为了解决这个问题，本研究提出了使用茶染色启发的化合物，单宁酸（TA）来处理细RCA。为此，首先将细RCA浸入TA的稀溶液中。在该过程中，TA可以与RCA的氢氧化钙（CH）和方解石反应，以在RCA颗粒的表面上产生纳米颗粒。这些纳米颗粒可以填充砂浆中的毛细纳米孔，显著降低所制砂浆的孔隙率。这可以通过扫描电子显微镜（SEM）和压汞孔隙率（MIP）分析来证实。实验研究了这种处理对用处理过的细RCA制成的砂浆的水化和力学行为的影响。试验结果表明，该方法可以显着提高砂浆的强度和耐久性，这可以主要归因于两个原因。首先，纳米压痕测试表明，在细RCA表面包覆TA可以捕获钙离子，诱导局部矿化，促进界面过渡区（ITZ）的水泥水化，使ITZ致密化。第二，硬化胶凝材料的内聚力可以通过TA的独特结合能力通过共价和非共价相互作用来增强。
A massive fraction of recycled concrete aggregates (RCAs) is fine RCA. Once recycled in new concrete, fine RCA can significantly reduce the mechanical strength and durability of the concrete since fine RCA has high water absorption and high porosity. To address this issue, this study proposes to treat the fine RCA using a tea-stain inspired compound, tannic acid (TA). To this end, fine RCA is first immersed in dilute solution of TA. In this process, TA can react with calcium hydroxide (CH) and calcite of RCA to produce nanoparticles on the surface of the RCA particles. These nanoparticles can fill the capillary nanopores in the mortar, significantly reduce the porosity of the produced mortar. This can be confirmed by the scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analysis. Experimental studies have been carried out to examine the effect of this treatment on the hydration and mechanical behavior of the mortars made with the treated fine RCA. Testing results confirm that the strength and durability of the mortar can be significant enhanced by the proposed method, which can be mainly attributed to two reasons. First, TA coated on the surface of the fine RCA can capture calcium ions to induce local mineralization and facilitate the hydration of cement in the interface transition zone (ITZ), densifying the ITZ according to nanoindentation test. Second, the cohesion of hardened cementitious material can be enhanced by the unique binding capacity of TA through covalent and non-covalent interactions.