Application of silica-rich biomass ash solid waste in geopolymer preparation: A review

Abstract

Silica-rich biomass ash (BMA), such as rice husk ash (RHA), sugar cane bagasse ash (SCBA), and corn cob ash (CCA), refer to solid waste that is generated from the combustion of biomass fuels. Unreasonable disposal of the ash can cause environmental pollution and the disposal costs can be pretty high. However, given its high silica content and pozzolanic activity, silica-rich BMA can be used as a sustainable building material. Previous studies have shown that it is reasonable to produce geopolymers (a green and low-carbon cementitious material with excellent physical and mechanical properties) through the utilization of silica-rich BMA. The present study reviews the latest research on the utilization of silica-rich BMA for geopolymer preparation. In this paper, the preparation of sodium silicate solution from silica-rich BMA is described in detail, and the differences between geopolymers made from commercial alkali activator solution and silica-rich BMA-derived solution are compared in terms of setting time and compressive strength. In addition, the paper also focuses on the effects of silica-rich BMA application as precursors on the properties of geopolymers. A proper amount of RHA has a positive effect on the mechanical strength, thermal stability, and water resistance of geopolymers. Appropriate levels of SCBA facilitate the later strength development as well as prolong the setting time of geopolymers. Moreover, CCA adversely affects the mechanical strength of geopolymers. More comprehensive research is needed in the future to efficiently utilize silicon-rich BMA for the production of sustainable geopolymers.