Title: Workability and Hydration of Superplasticized Cementitious Mixtures with Rice Husk Ash

Author(s): William Wilson and Arezki Tagnit-Hamou

Publication: Materials Journal

Volume: 111

Issue: 5

Appears on pages(s): 491-500

Keywords: hydration kinetics; mineral admixture; rice husk ash (RHA); shear thickening; strength; superplasticizer; supplementary cementitious material (SCM); viscosity; yield stress

DOI: 10.14359/51687100

Date: 9/1/2014

Abstract:
Rice husk ash (RHA) is a promising alternative cementitious material for use in sustainable concrete. While the performance and durability of RHA concrete has been extensively investigated, there is scant information on the interactions between RHA and superplasticizers (SPs). This paper thus focuses on the combined effects of RHA and five different SPs. Rheological investigations showed that high SP dosages were necessary because of the RHA particles’ water absorption. This reduction in available water led to an increased solid concentration and shear-thickening behavior. Calorimetric measurements showed that cement hydration was delayed by the elevated SP dosages (and not directly by the RHA). Moreover, dilution of the cement reduced the reaction intensity at early age. Using RHA increased compressive strengths at 28 days by up to 20%. Finally, this study illustrated the importance of preliminary SP optimization to fulfill the requirements of specific concrete applications.