纳米SiO2改性聚合物水泥基复合材料早期微观结构及性能

Microstructure and properties of polymer cement-based composites modified by nano SiO2 in early age

利用纳米SiO2(nano SiO2)早期可促进聚合物水泥基复合材料水化速率、提升其力学性能、改善其界面过渡区(ITZ)性能及优化其孔隙结构等特点,借助XRD、SEM、EDS、显微硬度(MH)及压汞(MIP)等试验,揭示了nano SiO2对聚合物水泥基复合材料早期性能影响的微观机制。结果表明:当nano SiO2掺量为2wt%时,聚合物水泥基复合材料的力学性能最优,3 d和7 d龄期抗压强度分别为57.5 MPa和67.3 MPa,较仅仅掺加聚合物的水泥基复合材料分别提高了12.7%和13.9%;nano SiO2的掺入改变了聚合物水泥基复合材料水化产物数量及微观形貌。对于ITZ性能,nano SiO2掺入后,聚合物水泥硬化浆体-骨料的ITZ厚度减小,形貌变得更加致密;ITZ的钙硅比因nano SiO2的加入变小而其显微硬度变大;此外,nano SiO2加入后可以进一步填充聚合物水泥基复合材料更加细小的孔隙,使其凝胶孔比例变高,最可几孔径变小,大大优化了聚合物水泥基复合材料的孔隙结构。

Owing to the addition of nano SiO2 can promote the hydration rate, improve the mechanical properties and interfacial transition zone(ITZ) and refine the pore structure of polymer cement-based composites, the microscopic mechanism of influence of nano SiO2 on the early properties of polymer cement-based composites was revealed by means of XRD, SEM, EDS, microhardness(MH) and mercury intrusion porosimetry(MIP) experiments.The results show that when nano SiO2 content is 2 wt%, the mechanical properties of the polymer cement-based composites are the best. The compressive strength is 57.5 MPa and 67.3 MPa in 3 d and 7 d age, respectively, which is 12.7% and 13.9% higher than that of the polymer cement-based composites with polymer simply. The addition of nano SiO2 changes the hydration products and microstructure of the polymer cement-based composites. As for ITZ,the thickness of ITZ between polymer cement hardened paste and aggregate decreases, its morphology becomes denser, the calcium-silicate ratio in ITZ declines and the microhardness in ITZ increases by nano SiO2 incorporation. Since nano SiO2 can further fill finer pores of the polymer cement-based composites, there is higher proportion of gel pores and the mean pore diameter tends to be smaller so that the pore structure of the polymer cementbased composites is greatly optimized by nano SiO2 addition.