蒸养混凝土的表层伤损效应

Surface Layer Degradation Effect of Steam-Cured Concrete

通过试验研究蒸养混凝土的毛细吸水性和氯离子扩散性能,分析蒸养混凝土表层与内部微观结构特征的差异,探讨了蒸养混凝土的表层伤损效应及其机理.结果表明:相对于标养混凝土,蒸养混凝土表层位置处(由表及里约10mm范围)的毛细吸水性及氯离子扩散速率均基本较大;蒸养过程会对混凝土表层微观结构造成显著的伤损,且这种伤损主要集中在混凝土由表及里约10mm范围;蒸养混凝土表层区较大的温度梯度及肿胀变形是蒸养混凝土产生表层伤损效应的根本原因;粉煤灰和矿渣掺入可在一定程度上降低蒸养作用对混凝土表层造成的伤损程度,有效提高蒸养混凝土抵抗水及氯离子迁移的能力.

Based on the experimental investigations of the capillary absorption of water and chloride diffu- sion of steam-cured concrete, the microstructure difference between surface layer and inner concrete was analyzed. The surface layer degradation effect and its mechanism of steam-cured concrete were also dis- cussed. The test results show that, compared with the standard cured concrete, both the capillary absorp- tion of water and chloride diffusion rate of steam-cured concrete are much higher at the surface layer（about 10 mm deep from the surface）. It can be found that the microstructure of surface layer is significantly dam- aged during steam curing, and the degradation effect mainly concentrates on the range of 10 mm deep from the surface. The main reasons for surface layer degradation effect of steam-cured concrete are the larger temperature gradient and the expansive deformation in concrete surface layer. The incorporation of fly ash and slag into concrete can alleviate the degradation of surface layer during steam curing, and effectively in- crease the resistance to ingress of water and chloride ion.