Compressive strength and degree of reaction of biomass- and fly ash-based geopolymer

Rice husk and bark ash (RHBA) was used as a rich SiO2 source to partially replace fly ash in making geopolymer. Consequently, the SiO2/Al2O3 ratio was extended to the wide range of 4.03–1035. Compressive strength, degree of reaction, and microstructure of the geopolymers were investigated to observe the effect of SiO2/Al2O3 ratio. Results revealed that the optimum SiO2/Al2O3 ratio to obtain the highest compressive strength was 15.9. Fly ash was more reactive than RHBA. It was also shown that not only the reactivity of the source materials but also the quality of the matrix contributed to the enhancement of compressive strength of the geopolymer paste.