膨胀剂对约束条件下UHPC早期抗裂性能影响的试验研究

超高性能混凝土(UHPC)在钢桥面铺装结构中由于铺装材料受到钢板、栓钉等的约束,加上材料本身水胶比小,更易收缩,早期容易承受拉应力导致开裂。通过在拌和过程中添加膨胀剂可以起到减小收缩的作用,但该方法对于约束条件下的UHPC铺装的早期抗裂性能提升是否有促进作用,仍需通过更多试验进行合理评估和深入研究。通过圆环法对3组不同配方的UHPC在均匀约束条件下的早期抗裂性能进行定量测试,并将试验数据进行回归分析和计算,得到了各组的平均应力发展速率,进而评估了各组的开裂风险等级。试验结果表明,通过在UHPC中加入适量膨胀剂,可使其最终收缩应力减小,并可降低其收缩应力发展速率,进一步降低其在约束条件下的开裂风险。

Experimental Study on the Effect of Expansion Agent on Early Crack Resistance Ability of UHPC under Restraint

Ultra high performance concrete(UHPC)is susceptible to have tensile stress cracking in the early stage in steel bridge pavement structuredue to the restraint of steel plate and stud on pavement and the low water-binder ratio of material that makes pavement easy to shrink.Adding the expansion agent during the mixing process can reduce the shrinkage of material.However,reasonable assessment and intensive study with more experiments should be done to decide whether the expansion agent has a good effect on the early crack resistance ability of UHPC under restraint.In this paper,the early crack resistance abilities under uniform restraint of three different groups of UHPC are quantitatively tested by ring test,and regression analysis and calculation are done with experiment data to get the average stress rate of each group,and then the potential for cracking of each group is evaluated.Test results show that adding the expansion agent moderately in UHPC will reduce the final shrinkage stress,lower the shrinkage stress rate,and bring down the potential for cracking under restraint.