Rice Husk Ash as a Partial Replacement of Cement in Concrete

Rice husk ash (RHA) is a silica-rich residue obtained from the combustion of rice husks. Its potential use as a supplementary cementitious material is of interest because Portland cement manufacture is carbon intensive and rice milling generates substantial agricultural residues. This paper critically reviews the mechanisms by which properly processed RHA affects concrete, identifies factors controlling performance, and proposes a laboratory program to compare ordinary concrete with mixtures incorporating 5%, 10%, 15%, and 20% RHA as a mass replacement for cement. The review considers ash production, amorphous silica, particle fineness, water demand, fresh properties, compressive and tensile strength, and durability. Existing studies support the feasibility of moderate cement replacement, but no single replacement percentage can be claimed optimal for all sources and mixture designs. A controlled experimental protocol and transparent results-reporting framework are developed for undergraduate research. Keywords Rice husk ash; supplementary cementitious material; pozzolanic reaction; sustainable concrete; compressive strength; workability; durability. Research questions How does replacement of cement with locally produced RHA affect workability and mechanical performance? Which processing and mix-design factors most strongly influence the result? Can the use of RHA reduce cement demand without compromising specified performance?