Influence of Expansion Agent and Shrinkage Reducing Agent on Autogenous Shrinkage of UHPC

To solve problems of high risk of shrinkage cracking of ultra-high performance concrete (UHPC), the effects of expansion agent and shrinkage reducing agent on the autogenous shrinkage of UHPC were researched in this paper. An experimental study on the slump flow, basic mechanical properties and autogenous shrinkage of UHPC with expansion agent or shrinkage reducing agent was carried out. On the basis of the experiment, the shrinkage reduction effect of the mixture of expansion agent and shrinkage reducing agent was investigated. The test results show that the slump flow of UHPC is increased by adding expansion agent or shrinkage reducing agent. The 28 days compressive strength is reduced by adding expansion agent or shrinkage reducing agent. The development of autogenous shrinkage of UHPC in each group can be divided into three stages: rapid development stage, slow development stage and stable stage. The autogenous shrinkage of UHPC in each stage was inhibited by the addition of expansion agent or shrinkage reducing agent. Among them, when the content of HP-CSA is 6.0%, the effect of shrinkage reduction is the best, and the reduction rate is 93.6% in 28 days. When the percent of SBT^®-SRA(I) is 1.5%, the effect of shrinkage reduction is the best, and the reduction rate is 43.0% in 28 days. There is no synergistic effect when expansion agent and shrinkage reducing agent are mixed.