Effect of rice husk ash addition on the compressive strength and thermal stability of metakaolin based geopolymer

The influences of rice husk ash incorporated as partial replacement (by up to 40%) of metakaolin on the thermal stability and microstructures of metakaolin based geopolymer were investigated in this paper. The results indicate that the aluminosilicate fractions of RHA were associated with the acid-base reaction of geopolymerization, promoting the more formation of gels. The pores of geopolymer were refined by the filling effects of rice husk ash and enrichment of gel phases, which were primary reason for the optimization of geopolymer thermal stability. The geopolymer added with RHA maintained excellent comprehensive performance in comparison to OPC paste after high temperature exposure. This is attributed to the different microstructure between geopolymer and OPC. Addition of 30% RHA would make the best contribution to the strength of geopolymer before or after temperature exposure significantly. (C) 2019 Elsevier Ltd. All rights reserved.