珊瑚砂负载减缩剂对超高性能混凝土基体性能的影响

Effect of coral sand loaded with shrinkage reducing agent on the properties of ultra-high performance concrete

超高性能混凝土(UHPC)在水化过程中伴随着较大的收缩,不利于其早期裂缝控制。针对此问题,以珊瑚砂负载减缩剂按照一定体积取代率取代石英砂配制UHPC,并根据相关标准对UHPC基体的工作性能、力学性能和体积稳定性进行了测试。结果表明:珊瑚砂负载减缩剂可以减弱减缩剂延缓水化的作用,增大UHPC基体的流动度,降低强度的发展;由于珊瑚砂内养护机制和减缩剂的协同作用,珊瑚砂负载减缩剂大幅减小了UHPC基体的自收缩和干燥收缩。最佳取代方式为以负载浓度30.8%减缩剂的珊瑚砂等体积取代45%的石英砂,UHPC基体的28 d抗压强度减小了14.9%,7 d自收缩减小了82.9%,28 d干燥收缩减小了54.1%,强度虽略有降低,但体积稳定性得到了良好的改善。

Large shrinkage usually occurs in the hydration process of ultra-high performance concrete(UHPC),which is not conducive to its early crack control.In order to solve this problem,UHPC was prepared by replacing quartz sand with coral sand loaded with shrinkage reducing agent according to a certain volume substitution rate,and the workability performance,mechanical properties and volume stability of UHPC were tested according to relevant standards.The results show that the coral sand loaded with shrinkage reducing agent can weaken the effect of shrinkage reducing agent on retarding hydration,increase the fluidity and reduce the development of compressive strength of UHPC.Due to the synergistic effect of the internal curing mechanism and shrinkage reducing agent in coral sand,the coral sand loaded with shrinkage reducing agent significantly reduced the autogenous shrinkage and drying shrinkage of UHPC.The optimum mixing is to replace 45%quartz sand with coral sand loaded with 30.8%shrinkage reducing agent.The 28 d compressive strength of UHPC decreases by 14.9%,the 7 d autogenous shrinkage decreases by 82.9%and the 28 d drying shrinkage decreases by 54.1%.Although the compressive strength reduces slightly,the volume stability of UHPC has been well improved.