Carbon Neutral Off-White Rice Husk Ash as a Partial White Cement Replacement

Large amounts of rice husk ash (RHA) are produced every year worldwide, and difficulties related to its disposal may cause this product to become an environmental hazard. Owing to its high amorphous silica content, RHA has shown to be a valid supplementary cementing material in the production of concrete. This paper presents the physical and chemical properties of a new generation RHA that is off-white in color, is carbon neutral, and has no crystalline SiO2 and toxic metals. The effects on mechanical properties of a mixture using off-white rice hull ash (OWRHA) as partial replacement of white cement were also investigated. The OWRHA-blended concrete has higher compressive and splitting tensile strengths at various ages compared with the control mixture. It is shown that up to 15% of OWRHA could be advantageously blended with white cement to enhance white concrete performance without modifying the aesthetics of the final product.