Use of rice husk ash for mitigating the autogenous shrinkage of cement pastes at low water cement ratio
It is well recognized that the high risk of early age micro crack of HPC/UHPC is attributed to the large magnitude of early age autogenous shrinkage caused by self desiccation in binder hydration. Over the years, several methods have been proposed to mitigate autogenous shrinkage based on internal curing theory, and a better internal curing agent is always being sought. Rice husk ash (RHA) was recognized having potencial to be an internal curing agent. In this paper, the effect of RHA on mitigating the autogenous shrinkage has been evaluated by different mean particle sizes of RHA, and the internal RH change was measured at the same situation. The results show a high efficiency of RHA for internal curing purpose, to drastically reduce the autogenous shrinkage of cement pastes. Comparing to the cement paste without RHA, the internal RH results show that the internal RH in pastes with RHA is evidently higher at either early or later ages. These were addressed in order to explain the mechanism RHA mitigates the autogenous shrinkage of pastes.