Microstructure of High Volume Rice Husk Ash Concrete

Abstract

Rice hush ash (RHA) is a promising supplementary cementitious material (SCM) and the application of concrete containing high volume SCMs is one of effective strategies to relieve the carbon emission from building industry. The effect of RHA contents up to 60% to replace cement on the microstructure evolution of concrete has been experimentally investigated through the compressive strength, nanoindentation and scanning electron microscope methods. The results indicate that the utilization of RHA reduces the early compressive strengths of concrete, but less than 40% RHA increases the later compressive strengths, the high volume RHA concrete showing the great development potentials of strengths. The utilization of less than 40% RHA improves the internal structures because of the active effect of RHA and the filling effect of unhydrated RHA. The utilization of RHA increases the proportions of high density calcium silicate hydrate (HD C–S–H) and ultra-high density C–S–H (UHD C–S–H) due to the fact that C–S–H produced by RHA is mainly composed of HD C–S–H and UHD C–S–H, and also improves the interfacial transition zone.