Potential of Rice Husk Ash (RHA) as a Supplementary Cementitious Material in Concrete

Supplementary cementitious material (SCM) is often used to make concrete more durable by improving its mechanistic properties. Rice husk ash (RHA) has the potential of being a SCM because of its pozzolanic activity. Arkansas produces a huge amount of RHA, which mostly originates from the world's largest rice miller, Riceland Foods, Inc. The RHA produced here is treated as an agricultural waste product and stored in nearby temporary storages, resulting in costly disposal processes as well as environmental hazards. Because the potential of this local RHA as a SCM has not been studied in the past, the present research study aims at exploring the potential of RHA as SCM through laboratory-based experiments. Three different graded RHA (600-RHA, 150-RHA, and 44-RHA) were incorporated in this study. The 600-RHA and 150-RHA were coarse in nature as they had a particle size of 600 mu m and 150 mu m, respectively, and did not meet the AASHTO M 321-04, Standard Specification for High-Reactivity Pozzolans for Use in Hydraulic-Cement Concrete, Mortar, and Grout, specification. The 600-RHA sample was collected from a plant site and was further ground to produce the 150-RHA sample. The 44-RHA sample was obtained from a commercial industry, and it was incorporated in this study for comparative analyses. Each type of RHA with two different percentages (10 % and 20 %) of replacement of Type I Ordinary Portland Cement (OPC) was investigated in this research. It was found that coarser RHAmodified concrete (600-RHA and 150-RHA) showed reduced strength properties while finer RHA (44-RHA) exhibited improved concrete properties. As a result, 44-RHA can be used as SCM in replacement of the OPC. The coarse RHA could be utilized in backfill and flowable fill as controlled low strength material. Further grinding of the coarse RHA followed by burning may improve the properties of modified concrete.