The Influence of Ground and Unground Rice Husk Ash on The Physico-mechanical and Microstructural Properties of Cement Mortars

Abstract

Superseding a portion of cement with agricultural wastes like rice husk ash (RHA) is an excellent solution to alleviate the ecological issues and resource depletion induced by cement production. In this paper, cement-based mortars were produced where Portland cement was replaced with ground or unground RHA (GRHA or URHA) from 0 to 12.5 wt% with an increment of 2.5% to investigate their effect on the fresh, physical, mechanical, and microstructural properties of mortars. GRHA inclusion up to 10% was advantageous due to the ameliorated physico-mechanical properties compared to other mixtures. In contrast, the introduction of URHA negatively affected the physical properties of mortars; however, the compressive strength values of URHA-containing mixtures were comparable to those of reference and GRHA mixes up to 7.5% replacement ratio. The macro-pores of mortars reduced with the incorporation of 10% GRHA or URHA, whereas the total porosity value increased with 10% URHA inclusion. The microstructural analysis suggested that the utilization of both GRHA and URHA decreased the portlandite content due to pozzolanic reactions. Hence, a relatively low amount of URHA compared to GRHA can also be efficiently used to produce mortar mixes without additional energy consumption and expense resulting from grinding.