Effect of Boric Acid on the Hydration of Rice Husk Ash Blended Cement

In the last decade, the use of supplementary cementing materials has become an integral part of high strength and high performance concrete mix design. These can be natural materials, by-products or industrial wastes, or the ones requiring less energy and time to produce. Some of the commonly used supplementary cementing materials are fly ash, Silica Fume (SF), Ground Granulated Blast Furnace Slag (GGBFS) and Rice Husk Ash (RHA) etc. Rice husk ash (RHA), produced by the controlled burning of the rice husk, is used as a highly reactive pozzolanic material. RHA additions in cement improve the properties of both fresh and hardened concretes. When the RHA is incorporated in the concrete, there are two possible reasons for the change in the hydration process, namely, the pozzolanic reaction of the amorphous phases in the RHA as a result of which more C-S-H gel may be formed in RHA concrete due to the reaction that probably occurs between the silica in RHA and the Ca2+, OH- ions, or Ca(OH)2 in hydrating cement and the filler effect. Chemical admixtures modify the process of hydration of RHA blended cement. Effect of boric acid on the hydration of RHA blended cement has been studied by using number of techniques. Results have been discussed.