减缩剂外涂对混凝土性能的影响及作用机理

FUNCTION AND MECHANISM OF SHRINKAGE REDUCING AGENT COATING CONCRETE

内掺减缩剂可有效降低混凝土收缩,但存在掺量大和影响混凝土强度发展等诸多问题。研究了减缩剂外涂对混凝土力学性能、收缩抗裂性能、孔结构和水化产物的影响。结果表明:减缩剂外涂混凝土的减缩效果明显;减缩剂外涂对混凝土和胶砂强度有一定的提高作用;与基准混凝土相比,减缩剂外涂可明显降低水泥石总孔隙率和孔径小于100nm毛细孔的数量;外涂减缩剂作用区域中的水泥水化产物更趋于丰富。

The shrinkage of concrete can be reduced effectively by adding shrinkage reducing agents （SRA）. However, the application of SRA requires a large dosage, leading to a high cost and some negative effects on the strength of concrete. The effects of the SRA coating on the mechanical performance, shrinkage-crack resistance, capillary structure and hydration products of concrete were investigated. The results show that the shrinkage reduction of concrete coated with the SRA is considerable. The strength of both concrete and mortar are not affected by the SRA coating, on the contrary, they are enhanced. The cumulative pore area and amount of capillary （≤100 nm） of harden cement paste are reduced after coating with the SRA compared to the standard paste. The coating with the SRA can accelerates the hydration of cement within the action range of the SRA.