高强复合骨料混凝土早期收缩研究

摘要

目的 研究高强混凝土的早期收缩性能,探讨饱水陶粒对混凝土早期收缩的影响,修正参数得到适宜高强混凝土收缩的数学模型,并对复合骨料高强混凝土收缩模型进行定义.方法 采用非接触式试验,将混凝土成型面暴露于室内空气中,带模测试了混凝土的早期收缩.结果 高强混凝土的收缩主要发生在14 h之内.14 h收缩值是3 d收缩值的92%,3 d收缩值为3 060μm·m-1;饱和吸水陶粒可改善高强混凝土早期收缩性能,陶粒的最佳体积替代量为41%,14 h、72 h收缩值降幅分别可达48%和43%.随着陶粒的增加,混凝土强度逐渐降低.结论 采用饱水陶粒替代混凝土中粗骨料,发挥其内养护作用,可以达到降低高强混凝土早期收缩的目的.修改后的超高强复合骨料混凝土收缩模型与试验结果吻合较好.%The purpose of this study is to research the shrinkage property of high strength concrete, and discuss the effect of saturated ceramsite on the shrinkage of high strength concrete at early age. To obtain suitable shrinkage model of high strength concrete, parameters are modified. And this paper presents a shrinkage model of high strength concrete with composite aggregate. The non-contact test method was applied to measure the early shrinkage. During test, the casting surface of the specimens in mould was exposed to air. The result shows that shrinkage mainly takes place within 14 h. The shrinkage at 14 h and 72 h are 2 815 μm·m-1 and 3 060 μm·m -1 respectively. Using saturated ceramsite can reduce the shrinkage of high strength concrete. The best volume substitution rate of ceramsite to coarse aggregate is 41％. shrikkage at 72 h could decline to 43％. With the increase of ceramsite, the compressive strength of concrete reduces gradually. Summing up the internal curing action of saturated ceramsite could reduce the early shrinkage of high strength concrete. The comparison result of test values and calculated values is acceptable.