Effect of rice husk ash on properties of slag based geopolymer pastes

Abstract

With the increasing commercialization of fly ash and slag, the price of slag is gradually increasing and there is a need to reduce slag consumption and utilize China's large rice husk production to introduce rice husk ash (RHA) as the raw material. In this experiment, the amount of RHA accounted for a high proportion (50%–80%), and the influence of the amount of RHA on compressive strength, flexural strength, water absorption and moisture absorption coefficient was studied. It is proposed that the degree of efflorescence can be judged according to the water evaporation rate, and the efflorescence degree can be quantitatively characterized by Image-Pro Plus® 6.0, mass weighing of efflorescence substance and pH measurement. In addition, microstructural experiments (SEM, XRD and MIP analysis) were also conducted to confirm the macroscopic experimental phenomena. The test results show that considering the compressive strength and flexural strength, 60% RHA and 40% slag (R6S4) are used together as the precursors to obtain the best mechanical properties. Increasing RHA can raises the water absorption performance, which can play the role of internal curing; meanwhile, it reduces the water evaporation rate by changing pore structure, and fewer free water as carriers inside the sample migrates to the outer surface, inhibiting efflorescence.