再生砖粉UHPC收缩性能试验研究

Experimental study on shrinkage of recycled brick powder UHPC

利用再生砖粉部分取代水泥制备混凝土是实现建筑垃圾再生利用的途径之一。采用活性激发后的砖粉作为辅助胶凝材料取代部分水泥制备UHPC,研究分析了不同取代率下再生砖粉UHPC的自收缩和干燥收缩规律与机理,基于试验建立了再生UHPC自收缩率和干燥收缩率预测模型。研究结果表明:再生砖粉取代水泥能够降低UHPC的自收缩,且UHPC的自收缩率随着砖粉取代率的增加而下降;再生砖粉取代水泥后能够减小UHPC的干燥收缩,且UHPC的干燥收缩随着砖粉取代率的增加呈先减小后增大的趋势。砖粉取代率为30%时,UHPC的干燥收缩最小,较之基准组降低了49.7%。自收缩率与干燥收缩率预测模型与试验结果吻合良好,能够用于预测再生砖粉UHPC的收缩发展。

Using recycled brick powder to partially replace cement to prepare concrete is one of the ways to realize the recycling of construction waste.The activated brick powder was used as an auxiliary cementing material to replace part of the cement to prepare UHPC.The law and mechanism of autogenous shrinkage and drying shrinkage of recycled brick powder UHPC under different substitution rates were studied and analyzed.Based on the experiments,a prediction model for the autogenous shrinkage and drying shrinkage of recycled UHPC was established.The results show that replacing cement with recycled brick powder can reduce the autogenous shrinkage of UHPC,and the autogenous shrinkage rate of UHPC decreases with the increase of the replacement rate of brick powder.The drying shrinkage of UHPC can be reduced by replacing cement with recycled brick powder,and the drying shrinkage of UHPC decreases first and then increases with the increase of the replacement rate of brick powder.When the brick powder replacement rate is 30%,the drying shrinkage of UHPC is the smallest,which is 49.7%lower than that of the baseline group.The autogenous shrinkage rate and drying shrinkage rate prediction models are in good agreement with the test results,and can be used to predict the shrinkage development of recycled brick powder UHPC.