预湿再生砂与膨胀剂协同作用对再生砂混凝土收缩性能的影响

Effects of Synergistic Action of Pre-Wetting Recycled Sand and Expansion Agents on Shrinkage Properties of Recycled Sand Concrete

为了降低再生砂混凝土的收缩变形,研究了预湿再生砂对混凝土工作性能、抗压强度、自收缩、干燥收缩及内部相对湿度的影响,并在此基础上掺入3种不同类型膨胀剂,进一步研究了预湿再生砂与膨胀剂协同作用对混凝土自收缩和干燥收缩的影响。结果表明:在附加用水量相同情况下,与采用绝干状态再生砂制备的混凝土相比,采用预湿再生砂制备的混凝土工作性能降低、强度增加,混凝土内部相对湿度更高,有效降低了其自收缩和干燥收缩;在掺入的3种膨胀剂中,钙质膨胀剂对混凝土自收缩的抑制效果最佳,钙镁复合膨胀剂对混凝土干燥收缩的抑制效果最佳;100%预湿程度下,与未掺膨胀剂混凝土相比,掺10%(质量分数)钙质膨胀剂的全再生砂混凝土的28 d自收缩降低了83.2%,掺6%钙镁复合膨胀剂的全再生砂混凝土的120 d干燥收缩则降低了36.1%。

In order to reduce the shrinkage of recycled sand concrete,the effects of pre-wetting recycled sand on working performance,compressive strength,autogenous shrinkage,dry shrinkage and internal relative humidity of concrete were studied.On this basis,three kinds of expansion agents were mixed into the concrete,and the effects of the synergistic action of pre-wetting recycled sand and expansion agents on the autogenous shrinkage and dry shrinkage of concrete were studied.The results show that under the condition of the same additional water consumption,compared with concrete prepared with recycled sand in absolute dry condition,the working performance of the concrete prepared by using prewetting recycled sand is reduced,the strength is increased,and the internal relative humidity can be maintained at a higher level,which effectively reduces its autogenous shrinkage and dry shrinkage.Among the three kinds of expansion agents mixed into the concrete,calcium expansive has the best inhibition effect on the autogenous shrinkage of concrete,and calcium magnesium complex expansion agents have the best inhibition effect on the dry shrinkage of concrete.At 100%pre-wetting degree,compared with concrete without expansion agents,the autogenous shrinkage of the 10%calcium specimen of the fully recycled sand concrete is reduced by 83.2%,and the dry shrinkage of the 6%calcium magnesium complex specimen of the fully recycled sand concrete is reduced by 36.1%.