Effect of napier grass ash on the autogenous shrinkage of low water binder ratio cement based materials

This work presents an experimental investigation on the effect of Napier grass ash (NGA) on the early age autogenous shrinkage of NGA blended cement paste with low water/binder ratio. Further burnt process was conducted on the as received raw NGA to decrease the carbon content, and comparison study was performed. Comprehensive tests were performed on the sealed samples to evaluate the behavior of autogenous shrinkage and self-desiccation in NGA blended cement pastes with low water/binder ratio 0.25. The autogenous shrinkage was conducted according to the standard method ASTM C1698. Setting time was determined by the Vicat needle apparatus according to the standard method ASTM C191. Internal RH measurement was performed to reveal the self-desiccation process of the sealed cement pastes at very early age. Considering the relationship between the self-desiccation and autogenous shrinkage of cementitious materials, a new ‘time zero’ was proposed. The effect of replacement of cement by NGA on the autogenous shrinkage of low water/binder ratio cement pastes was revealed by comparison study between the autogenous shrinkage measured from final setting time as defined in standard method ASTM C1698 and the new ‘time zero’.