Correlating Self-Consolidating Concrete mixture composition to its rheological properties

Abstract

Self-Consolidating concrete (SCC), a highly flowable concrete, is gaining wide acceptance in the concrete industries due to a higher productivity, lower energy consumption, improved working environment and increase quality. SCC is susceptible to segregation and therefore a balance between flow-ability and stability is required. The absence of a comprehensive SCC mixture composition design guidelines merits investigating the effects of SCC mixture variables on the properties affecting its performance, namely flow and stability.

An experimental and analytical study were carried out to study the influence of 5 design variables, namely water to binder ratio (w/b), percent addition of silica fume (SF), percent addition of Ground Granulated Blast Furnace Slag (GGBFS), bulk volume of coarse aggregates and binder content, on the workability and rheology of SCC. Workability measurements, specifically the slump flow, T50, L-Box and segregation column, and rheological properties, namely plastic viscosity, yield stress, and thixotropy were measured to evaluate SCC’s performance. A revised modified Bingham model was proposed to adequately account for the linear and non-linear responses of the concrete flow. It postulates that the flow is divided into a linear and non-linear part. The revised model is found to provide more consistent and precise estimate of the rheological properties. Using regression analyses, yield stress and plastic viscosity models that account for the statistically significant variables were derived from experimental test data. Yield stress is found to depend on the bulk volume fraction of the coarse aggregate, Silica Fume content, High Range Water Reducing Agent (HRWRA) and Viscosity Modifying Agent (VMA), and plastic viscosity on w/b, HRWRA and Average Paste Thickness (APT).