LAUSR

Abstract The demand for concrete continues to grow with increases in population and increased urbanization. This demand, in turn, increases the need to reduce the environmental impacts of concrete while continuing to provide the same or better performance. Increasing population also creates growing demand for food and energy resources. The cultivation of rice, the staple food of over half the world's inhabitants, results in the production of additional biomass. Rice biomass, such as hulls and straw, can be combusted as a renewable energy source and, under specific combustion conditions, the resulting ash can be used as a supplementary cementitious material or beneficial filler in the production of concrete, which can potentially lead to reduced environmental impacts in concrete. This paper reviews rice-based ash and its influence on concrete properties to address current understanding of these ashes as an alternative mineral admixture. The review of the literature shows that under proper combustion conditions as well as through use of pre- and post-combustion treatments, highly pozzolanic (reactive) ash can be produced from rice hulls. These reactive ashes have the ability to improve several properties of concrete when used as a partial replacement for cement. Additionally, the production of rice-based ash can offer a lower greenhouse gas emitting pozzolan than portland cement and some conventional supplementary cementitious materials. Further research into the utilization of rice-straw ash, durability properties, and high performance concrete could lead to the production of rice ash as a cost- and environmentally-competitive alternative in the production of concrete.