膨胀剂、减缩剂对超高性能混凝土自收缩性能的影响

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

    • 摘要: 为了解决超高性能混凝土(ultra-high performance concrete,UHPC)存在的收缩开裂风险高等问题,研究膨胀剂、减缩剂对UHPC自收缩性能的影响,开展单掺膨胀剂或减缩剂UHPC的扩展度、基本力学性能及自收缩规律的试验研究,并在此基础上对膨胀剂与减缩剂双掺后的减缩效果进行研究.试验结果表明,膨胀剂或减缩剂单掺均提高UHPC扩展度;膨胀剂或减缩剂单掺均降低28 d抗压强度;掺膨胀剂、减缩剂UHPC的28 d自收缩发展可分为3个阶段:快速发展期、缓慢发展期、平稳期;单掺膨胀剂或减缩剂均有效抑制UHPC各阶段的自收缩,其中,膨胀剂HP-CSA质量分数为6.0%时减缩效果最佳,28 d减缩率达93.6%,减缩剂SBT®-SRA(I)质量分数为1.5%时减缩效果最佳,28 d减缩率为43.0%;膨胀剂与减缩剂双掺时未产生协同效应.

       

      Abstract: 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.

       

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