基于MMA浸渍-聚合的再生粗骨料复合改性

Composite Modification Method of Recycled Coarse Aggregate Based on MMA Impregnation-Polymerization

摘要:

为了改善再生混凝土性能差、性能离散性较大的问题，采用水泥浆裹浆+甲基丙烯酸甲酯单体（MMA）浸渍-聚合的方法对再生粗骨料进行改性，研究了水灰比和MMA聚合温度、聚合时间、聚合环境等对MMA复合改性效果的影响。结果表明：当水灰比为0.5，浸渍时间为24 h，聚合温度为70 ℃，密封环境下聚合时间为24 h时，再生粗骨料的改性效果最好；MMA复合改性后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62.50 nm降到了5.93 nm，有害孔和多害孔的含量下降了74.9%；当再生粗骨料取代率为33%、66%和100%时，MMA复合改性再生粗骨料混凝土的28 d立方体抗压强度相较于普通再生粗骨料混凝土分别提高了5.9%、9.5%和12.7%，28 d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显著提高了再生混凝土的力学性能。

Abstract:

To solve the problem of the poor performance and high discreteness of recycled coarse aggregate concrete（RAC）， a composite modification method combining cement paste pretreatment with methyl methacrylate monomer（MMA） impregnation-polymerization was investigated. The effects of the water-cement ratio， along with the polymerization temperature， time， and environment of MMA， on the performance of MMA composite-modified recycled coarse aggregate（RCA） were investigated. The results demonstrate that optimal modification is achieved with a 0.5 water-cement ratio， 24 h MMA impregnation and 24 h polymerization at 70 ℃ in a sealed environment. After MMA composite modification， there are 70.3% reduction in water absorption， 41.9% decrease in crushing index， and 83.1% reduction in porosity of the RCA. The most probable pore diameter decreases from 62.50 nm to 5.93 nm， with total harmful and multi-harmful pore content reduces by 74.9%. Compared with conventional RAC， the 28 d cube compressive strength of modified recycled coarse aggregate concrete increases by 5.9%， 9.5%， and 12.7% respectively， while the axial compressive strength improves by 4.1%， 9.1%， and 14.1% respectively. The mechanical properties of RAC are significantly enhanced following MMA composite modification RCA.