粉煤灰对水泥浆体自收缩和抗压强度的影响

Effect of Pulverized Fuel Ashes on Autogenous Shrinkage and Compressive Strength of Cement Pastes

设计组装了水泥浆体自收缩测量装置,进行了不同粉煤灰掺量和水胶比的水泥浆体自收缩和抗压强度测试,采用压汞测孔仪(MIP)、扫描电镜(SEM)等测试技术研究了粉煤灰对水泥浆体孔结构、产物形貌等微观结构的影响,并对其影响机理进行了分析.结果表明:粉煤灰能够有效抑制水泥浆体的早期自收缩,在7 d前,其自收缩随着粉煤灰掺量的增加而减小;与纯硅酸盐水泥浆体相比,粉煤灰水泥浆体7 d后的抗压强度增幅较大,但自收缩增长速率也趋于增大;火山灰反应引起的孔径细化、水化产物结构致密是粉煤灰影响水泥浆体自收缩和抗压强度的根本原因.

Autogenous shrinkage of cement pastes with different contents of pulverized fuel ashes(PFA) and different water-to-binder ratio were measured by a shrinkage test device.Compressive strength of sealed cement paste were also measured.The influence of PFA on the pore structures and micrograph of hydration products were investigated through mercury intrusion porosimetry(MIP) and scanning electron microscopy(SEM),on which the influence mechanism was analyzed.Experimental results demonstrated that autogenous shrinkage of cement pastes decreased with the increased contents of PFA at early age(before 7 d),this may be ascribed to inhibition of PFA on the shrinkage.After 7 d,however,both autogenous shrinkage,and compressive strength of cement pastes increased.This may be attributed to decrease of pore radius and densification of cement hydration products due to the pozzolanic reaction of fly ash.