再生粗骨料硅烷浸渍处理对混凝土介质传输性能的影响

Effect of recycled coarse aggregate after strengthening by silane impregnation on mass transport of concrete

由于残余砂浆的存在,再生粗骨料的物理力学指标远不及天然骨料,致使再生混凝土力学和耐久性能较差;此外,水分及有害离子侵入混凝土内部是引起混凝土材料性能劣化的主要原因。本试验用质量分数为8wt%的硅烷乳液浸渍强化再生粗骨料,通过抗压强度、毛细吸水和抗氯离子侵蚀试验对硅烷浸渍前后不同骨料质量取代率(0%、30%、50%)的再生混凝土介质传输性能进行了研究,最后利用SEM对再生混凝土内部的微观结构进行分析。试验结果表明,硅烷浸渍处理再生粗骨料的吸水率显著降低,由其制备的混凝土强度稍有所下降;再生混凝土毛细累积吸水量明显减少,且抗氯盐侵蚀性能显著提高,其中骨料质量取代率为50%的再生混凝土浸渍处理后氯离子扩散系数降低了37.5%。研究表明,硅烷浸渍处理再生粗骨料是提高再生混凝土耐久性的有效途径。

The physical index of recycled coarse aggregate is far lower than that of natural coarse aggregate due to the existence of residual mortar, which leads to the poor mechanical properties and durability of recycled aggregate concrete(RAC). Furthermore, the ingress of water and aggressive ion is the main cause of the degradation of concrete properties. The durabilities of concrete with various replacement ratios by mass of recycled concrete aggregate(0%, 30%, 50%), which has been impregnated by 8 wt% silane, were studied through a series of tests, including the compressive strength, capillary water absorption and chloride penetration depth. Finally, the microstructure of the recycled concrete was analyzed by SEM. The experimental results show that the water absorption rate of the recycled coarse aggregate treated by silane impregnationis decreases significantly, and the compressive strength of the recycled concrete prepared by silane decreases slightly. Moreover, the capillary water absorption of the modified recycled concrete is obviously reduced while the chloride penetration resistance is significantly increased.The chloride diffusion coefficient of the treated recycled concrete with the aggregate replacement ratio by mass of 50% is reduced by 37.5%. This research indicates that the recycled coarse aggregate impregnated by silane is an effective way to improve the durability of the recycled aggregate concrete.