Abstract

Crushed brick-concrete recycled aggregate (BCRA) represents a sustainable and environmentally friendly alternative to natural aggregates (NAs) in practical engineering. However, compared with NA, the high porosity and low strength of BCRA means it struggles to meet engineering requirements, which limits its large-scale application. This paper reports upon an experimental study to enhance the quality of BCRA via soaking in different types of solutions (pozzolanic materials, sodium silicate, polyvinyl alcohol, and silicon-based additive). The physical and mechanical properties of treated and untreated BCRA were evaluated by testing the apparent density, water absorption, and crushing value. Meanwhile, the optimization schemes for different treatment techniques were recommended using the multi-objective grey target decision method. In addition, the surface morphology of BCRA was characterized by X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy, to examine the microstructure of the BCRA surface before and after different treatment processes. The results show that 80% cement, 10% fly ash, and 10% silica fume slurries had notable effects on the apparent density and mechanical strength of BCRA, in which the apparent density increased by 0.6–1.8% and the crushing value decreased by 3.5–19.7%; however, the water absorption of BCRA increased by 1.7–8.5%. The physical and mechanical properties of BCRA increased under an increase of sodium silicate concentration and soaking time, though its strengthening effects were limited. Polyvinyl alcohol and silicon-based additives were best able to improve the waterproofing of BCRA, and the water absorption of the BCRA after treatment was reduced by 5.1–17.8% and 30.5–44.9%, respectively. Clear microstructural improvements can also be observed on the treated BCRA surface. To summarize, the BCRA treated by the four treatment methods exhibited surfaces that were denser, less porous, and more homogeneous and regular. These results will provide a useful reference for the future engineering applications of treated BCRA.

摘要

碎砖-混凝土再生骨料 (BCRA) 是实际工程中天然骨料 (NA) 的可持续和环保替代品。但与NA相比，BCRA孔隙率高、强度低，难以满足工程要求，限制了其大规模应用。本文报道了一项通过以下方式提高 BCRA 质量的实验研究浸泡在不同类型的溶液（火山灰材料、硅酸钠、聚乙烯醇和硅基添加剂）中。通过测试表观密度、吸水率和压碎值来评估处理和未处理的 BCRA 的物理和机械性能。同时，采用多目标灰色目标决策方法推荐不同处理技术的优化方案。此外，通过 X 射线衍射和扫描电子显微镜结合能量色散光谱对 BCRA 的表面形貌进行了表征，以检查不同处理工艺前后 BCRA 表面的微观结构。结果表明，80% 的水泥、10% 的粉煤灰和 10% 的硅灰浆料对 BCRA 的表观密度和机械强度有显着影响，其中表观密度增加0.6-1.8%，压碎值降低3.5-19.7%；然而，BCRA 的吸水率增加了 1.7-8.5%。BCRA的物理力学性能随着硅酸钠浓度和浸泡时间的增加而增加，但其强化效果有限。聚乙烯醇和硅基添加剂对 BCRA 防水性能的改善效果最好，处理后 BCRA 的吸水率分别降低了 5.1-17.8% 和 30.5-44.9%。在处理过的 BCRA 表面上也可以观察到明显的微观结构改进。综上所述，四种处理方法处理的 BCRA 表面更致密、孔隙更少、更均匀和规则。