Mechanical properties, microstructure and drying shrinkage of hybrid fly ash-basalt fiber geopolymer paste

This paper evaluates the mechanical properties, microstructure and drying shrinkage of hybrid fly ash-basalt fiber geopolymer paste. Fly ash was replaced with basalt fiber at the replacement levels of 0, 10, 20, 30, 40 and 100%. Na2SiO3/NaOH ratio of 1.0 and liquid to binder (L/B) ratio of 0.60 were used for making geopolymer pastes. Setting time, strength and drying shrinkage of geopolymer pastes were tested. The results showed that the replacement of fly ash with basalt fibers in geopolymer pastes resulted in increased setting times and strength and reduced drying shrinkage of paste. The basalt fiber acted as small reinforcing fibers and enhanced the development of CSH, CASH and NASH which further enhanced the properties of paste. In addition, the total porosity and critical pore size of fly ash geopolymer paste reduce with increasing replacement content in fly ash which makes the paste more homogeneous and dense compared to fly ash geopolymer.