硫酸盐侵蚀溶液pH值对硅酸盐水泥浆体C-(A)-S-H凝胶结构的影响

摘要

C-(A)-S-H凝胶的结构不仅受水泥基材料自身组成的影响,更受其所处环境的影响.本文利用固体核磁共振(NMR)并结合去卷积技术,探究硫酸盐侵蚀溶液pH值对硅酸盐水泥浆体中C-(A)-S-H凝胶结构的影响.结果表明:硫酸盐侵蚀过程中,前期进入凝胶中的Al 3+后期又会脱出,使凝胶中四配位铝(Al[4])/Si比值降低.侵蚀溶液pH值的降低促进了凝胶中Al[4]的脱出,使Al[4]的峰位向负值移动;同时也促进了[SiO4]([AlO4])四面体间的聚合,使C-(A)-S-H凝胶平均分子链长(MCL)增加.此外,侵蚀溶液pH值的降低,促进了浆体的水化,但抑制了浆体中钙矾石(AFt)的生成.%C- (A) -S-H gels are not only affected by the composition of cement-based materials, but also affected by the environment.The effect of pH-values of Na2 SO4 solution on the structure of C- (A) -S-H gels was studied by solid-state nuclear magnetic resonance (NMR) with deconvolution technique.The results show that the Al[4]/Si value of C- (A) -S-H gels decreases in sulfate attack process, due to Al 3+entering into gel early and coming out later.The decrease of the erosion solution pH value promotes the migration of Al[4]from C-S-H gels, which leads to the peak position of Al[4]shifting to a negative value.It is found that the average molecular chain length (MCL) of C-S-H gel increases due to the polymerization among[SiO4] ([AlO4]) tetrahedra.In addition, the degree of hydration of the pastes is improved with the decrease of the pH-value, which is not favorable to formation of AFt.