Effects of Mixing Time and Revolution Count on Characteristics of Blended Cement Containing Rice Husk Ash

Abstract

Standard specifications for ready-mixed concrete (RMC) specify a limit of mixing time and revolution count of a RMC truck. More than half of today’s RMC contains a blended cement and chemical admixture. For this reason, the current specification may be outdated. This paper aims to gain technical knowledge on a behavior of mixing time and revolution count of the blended cement system containing rice husk ash (RHA) and chemical admixture. This paper assesses the effects of mixing time and revolution count on ion concentration, flowability, setting time, chemical shrinkage, porosity, compressive strength, and chloride diffusivity of pastes and mortars containing several types of RHA. The RHA types evaluated include as-received RHA (AR-RHA), chemically transformed (alkali-treated) RHA, and AR-RHA with retarder. Results indicate that although the mixing conditions influence the characteristics of the blended cement system, RHA type has a greater effect on these characteristics. Controlling the performance of RMC can be achieved by selecting the proper RHA type to add into the mixture.