Chapter 5: Effects of paste-to-voids volume ratio on performance of self-consolidating concrete mixtures

A well-proportioned self-consolidating concrete (SCC) mixture can be achieved by controlling the aggregate system, paste quality and paste quantity. This study aims to apply a concept that is based on paste-to-voids volume ratio (V_paste/V_voids) to assess the performance of SCC mixtures. The relationship between excess paste theory and V_paste/V_voids was investigated. Tests were conducted on a large matrix of SCC mixtures that were designed for cast-in-place concrete construction. The mixtures were made with different aggregate types and sizes, and different cementitious materials. The workability, flow properties, compressive strength, shrinkage and surface resistivity of SCC mixtures were determined as indicators of SCC performance. Statistical analyses, response surface models and Tukey honest significant difference (HSD) tests, were conducted to relate the mix design parameters to the concrete performance. Test results revealed that slump flow of the SCC mixtures increased with V_paste/V_voids at a given viscosity. Strength increases with V_paste/V_voids up to a point (∼150%), after which the strength becomes independent of V_paste/V_voids. V_paste/V_voids has little effect on the shrinkage of SCC mixtures, or their surface resistivity. Statistical analysis is an efficient tool to identify the significance of influencing factors on concrete performance.