Effect of silane coupling agent on the rheological and mechanical properties of alkali-activated ultrafine metakaolin based geopolymers

Abstract

Fluidity modification on geopolymer without changing its compositions is necessary. This study, firstly, investigated the optimal oxides molar ratios of geopolymers, then rheology, rheokinetics, fluidity and mechanical properties tests were conducted to study the influence of silane coupling agent (SCA) on geopolymers. Finally, characterization techniques of SEM, pore size distribution, FTIR and DSC were used to reveal the mechanisms. The results show when SiO2/Al2O3 = 3.4, M2O/Al2O3 = 1, and H2O/M2O = 11, geopolymer’s fluidity reaches 144 mm with the best compressive strength. The addition of 2 wt% SCA can reduce viscosity, increasing the fluidity to 167 mm, while excessive SCA can’t. SCA can also increase the viscosity growth rate and influence the microstructure of geopolymers.