Effects of Rice Husk Ash on the Shrinkage and Cracking Behavior of Geopolymer Concrete
Geopolymer concretes usually exhibit severe volume shrinkage behavior,which restricts the applications in construction engineering.To enhance the volume stability of fly ash-slag based geopolymer concretes,rice husk ash was incorporated into the concretes.The strength development and shrinkage behavior of concretes were investigated,and BET nitrogen adsorption technique and scanning electron microscope(SEM)were used to characterize the microstructure.The results showed that the rice husk ash exhibited a relatively high reactivity in the geopolymer binder.The rice husk ash addition could accelerate the kinetics of alkali-activation,and thus enhance the compressive strengths of concretes.The autogenous shrinkage and drying shrinkage were both mitigated.The autogenous shrinkage and drying shrinkage of concretes with 20%rice husk ash addition were 56.2 μm/m and 447.9 μm/m,respectively.Comparing with the pure geopolymer concrete,the autogenous and drying shrinkage reducing rates of rice husk ash-modified concretes were 62.4%and 48.0%,respectively.The rice husk ash particles adsorbed water from the aqueous alkaline activators.This was helpful in maintaining the relative humidity within the geopolymer binder.In addition,the rice husk ash addition also reduced proportion of capillary pores in geopolymer to compact the pore structure.The cracking development in microstructure was also restricted.
国家科技期刊平台
NSTL
万方数据
维普
