The use of rice husk ash as reactive filler in ultra-high performance concrete

In this study, rice husk ash (RHA)-based reactive filler was used in ultra-high performance concrete (UHPC) to improve mechanical properties without heat-treatment. This strategy replaces inert quartz filler with the reactive RHA filler, to increase the amorphous silica content while maintaining the physical role of the micron-sized quartz filler. Due to the high porosity of RHA, internal curing is effective, which promotes the hydration reaction over a long period of time. Experimental results show an outstanding strength around 200 MPa after 91 days, under ambient conditions (20 °C and 60% relative humidity). This was possible due to the promotion of pozzolanic reaction by additional water and amorphous silica provided by the porous (i.e., internal curing effect) and reactive filler, respectively; hence, the volume of capillary pores was reduced. The result reported herein will further promote the utilization of agricultural byproduct for the development of reactive RHA-based construction materials.