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

Abstract Rice husk and bark ash (RHBA) was used as a rich SiO 2 source to partially replace fly ash in making geopolymer. Consequently, the SiO 2 /Al 2 O 3 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 SiO 2 /Al 2 O 3 ratio. Results revealed that the optimum SiO 2 /Al 2 O 3 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.