Eco-friendly treatment of recycled concrete fines as supplementary cementitious materials
Eco-friendly treatment of recycled concrete fines as supplementary cementitious materials
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作为辅助胶凝材料的再生混凝土细粉的环保处理
DOI：
10.1016/j.conbuildmat.2022.126491
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发表时间：
2022
影响因子：
7.4
通讯作者：
Xu, Ying
中科院分区：
文献类型：
--
作者：
Wang, Liang;Wang, Jialai;Wang, Hao;Fang, Yi;Shen, Wenfeng;Chen, Peiyuan;Xu, Ying
拆除或废弃的混凝土可粉碎成适当尺寸的颗粒，用作新混凝土中的粗骨料或细骨料。该回收过程还产生5%至20%的尺寸小于0.15 mm的小颗粒。其可以作为再生混凝土细粉（RCF）回收。除了低端应用和垃圾填埋外，很少发现区域合作框架的适当应用。本研究开发了一种生态友好的处理方法，将这些未充分利用的RCF转化为新混凝土的补充胶凝材料（SEM）。在不进行任何处理的情况下，RCFs由于其低火山灰活性和高孔隙率而可以显著降低所生产的混凝土的强度和耐久性。本研究利用一种植物基化合物单宁酸（TA）来处理RCF，使它们可以用于新的混凝土中，以部分取代波特兰水泥，而不降低混凝土的性能。这是通过简单的两步混合过程完成的。在第一步中，将RCF颗粒与低浓度TA溶液混合约1小时，以允许TA和RCF颗粒之间的潜在反应。在步骤II中，将由步骤I产生的浆料与水泥和骨料混合以制造混凝土。TA和RCF颗粒之间的反应可以产生沉积在RCF颗粒表面上的亚微米颗粒。这些颗粒不仅填充RCF颗粒的孔隙，而且还为水泥的水化提供成核位点。这促进了水泥的水合作用，并使硬化浆体的微观结构致密化。因此，所提出的TA处理可以产生多种益处。实验结果表明，高达26%的砂浆的抗压强度的增量已实现拟议的处理。更重要的是，降低了砂浆早期开裂的风险，大大提高了钢筋的腐蚀寿命。
Demolished or waste concretes can be crushed into particles with appropriate sizes to be used as coarse or fine aggregates in new concretes. This recycling process also produces 5% to 20% small particles with size less than 0.15 mm. which can be recycled as the recycled concrete fines (RCFs). Besides low-end applications and landfilling, few appropriate applications have been found for RCF. This study develops an eco-friendly treatment to turn these underutilized RCFs into supplementary cementitious materials (SEM) for new concretes. Without any treatment, RCFs can significantly reduce the strength and durability of the produced concrete due to their low pozzolanic activity and high porosity. This study exploits a plant-based compound, tannic acid (TA) to treat RCFs so they can be used in new concrete to partially replace Portland cement without reducing the performance of the concrete. This is done by a simple two-step mixing process. In the first step, RCF particles are mixed with a low-concentrated TA solution for about one hour to allow for potential reaction between the TA and the RCF particles. In step II, the slurry produced by step I is mixed with cement and aggregate to make concrete. Reaction between the TA and the RCF particles can produce submicron particles deposited on the surface of the RCF particles. Those particles not only fill the pores of the RCF particles, but also provide the nucleation sites for the hydration of the cement. This promotes the hydration of the cement and densifies the microstructure of the hardened paste. As a result, multiple benefits can be induced by the proposed TA treatment. Experimental results show that up to 26% increment in compressive strength of the mortar has been achieved by the proposed treatment. More importantly, the risk of cracking in the early age of the mortar is reduced and the corrosion life of the reinforcing bar is greatly enhanced.