Autogenous shrinkage and hydration property of cement pastes containing rice husk ash

In this paper, the rice hush ash (RHA) with different particle size were applied to explore its effect on the autogenous shrinkage and hydration property of cement pastes. The water absorption/ release behavior of RHA in cement pastes were characterized by using 1H nuclear magnetic resonance. Additionally, the microstructure and compressive strength of cement pastes containing RHA were also measured. Experimental results showed that water absorption capacity of raw RHA in cement pastes reached 0.89 g/g due to its porous structure, but reduced with the decrease of RHA particle size. The addition of RHA could mitigate the development of self-desiccation, being ascribed to the release of water from RHA after about 12 h which decreased the con-sumption of capillary water. The autogenous shrinkage of cement pastes containing RHA was reduced by about 41.6 %, 35.6 % and 23.8 %, respectively when the mean particle size of RHA decreased from 43.6 mu m to 8.5 mu m. Furthermore, the addition of RHA could shorten the dormant period and greatly enhance early-age compressive strength of cement pastes due to its water absorption effect. At later ages, the hydration degree of cement was continuously increased under the double effect of internal curing and pozzolanic reaction of RHA, resulting in the formation of the dense interfacial transition zone (ITZ) between matrix and RHA particles, ultimately improved long-term strength.