基于MMA浸渍-聚合的再生粗骨料复合改性研究

Research on composite modification method of recycled coarse aggregate based on MMA monomer impregnation polymerization

摘要:

再生粗骨料较差的物理力学性能是造成再生混凝土（RAC）性能差，性能离散性较大的主要原因。为改善再生混凝土的性能，加速再生混凝土在工程中的推广应用，本文采用水泥浆预处理+甲基丙烯酸甲酯（MMA）单体浸渍-聚合的复合方法对再生粗骨料的改性进行了探究。研究了水泥浆水灰比，以及聚合温度、聚合时间和聚合环境等因素对MMA复合改性再生粗骨料性能的影响。研究结果表明，水泥浆水灰比为0.5，MMA单体浸渍24h后在70℃密闭环境下聚合24h的再生粗骨料改性效果最好，再生粗骨料的吸水率下降了70.3%，压碎指标下降了41.9%，孔隙率下降了83.1%，最可几孔径由625?降到了59.3?，有害孔和多害孔总孔隙含量下降了74.9%，由0.0331ml/g降到了0.0083ml/g，MMA复合改性后再生粗骨料的物理性能和孔隙结构均得到了显著改善。基于以上研究结果，以再生粗骨料取代率为参数（0%，33%、66%、100%），对MMA复合改性再生粗骨料混凝土的力学性能进行了研究。研究结果表明，相较于普通再生混凝土，再生粗骨料取代率为33%，66%和100%时，MMA复合改性后再生混凝土28d立方体抗压强度分别提高了5.9%、9.5%和12.7%，28d轴心抗压强度分别提高了4.1%、9.1%和14.1%。MMA复合改性再生粗骨料后显著提高了再生混凝土的力学性能。

Abstract:

The inferior physical and mechanical properties of recycled coarse aggregates (RCA) are the main reasons for the poor performance and high discreteness of recycled aggregate concrete (RAC). To improve the performance of recycled concrete and accelerate its engineering application, this study investigated a composite modification method combining cement slurry pretreatment with methyl methacrylate (MMA) monomer impregnation-polymerization. The effects of water-cement ratio of cement slurry, as well as polymerization temperature, duration, and environment on the performance of MMA-modified RCA were systematically examined. Results demonstrate that optimal modification was achieved with a 0.5 water-cement ratio cement slurry pretreatment, followed by 24-hour MMA impregnation and 24-hour polymerization at 70°C in a sealed environment. The modified RCA showed remarkable improvements: 70.3% reduction in water absorption, 41.9% decrease in crushing index, and 83.1% reduction in porosity. The most probable pore diameter decreased from 625? to 59.3?, with total harmful and multi-harmful pore content reduced by 74.9% (from 0.0331 mL/g to 0.0083 mL/g), indicating significant enhancement in both physical properties and pore structure. Based on these findings, mechanical properties of MMA-modified RAC with different replacement rates (0%, 33%, 66%, 100%) were investigated. Compared with conventional RAC, the 28-day cube compressive strength of modified RAC increased by 5.9%, 9.5%, and 12.7% respectively at corresponding replacement rates, while the axial compressive strength improved by 4.1%, 9.1%, and 14.1%. These results The mechanical properties of RAC were significantly enhanced following MMA composite modification RCA.