Robust SCC Mixes through Mix Design

Abstract

One of the main obstacles to a wider use of self-compacting concrete (SCC) is its sensitivity to small variations of the constituent materials, mix proportions, and other external factors. The main objective of this paper is to illustrate how to evaluate and compare the robustness of SCC mixtures optimized according to various economic criteria while maintaining the water/cement ratio and fresh state target properties. The optimization is derived from numerical models, and a central composite design is developed to mathematically model the influence of mixture parameters and their coupled effects on deformability, passing and filling abilities, and compressive strength. The strategies to increase the robustness of SCC mixtures and the existing methodologies to assess it are presented and discussed. By applying these methodologies, it is shown that robustness can be enhanced by changing only the proportions of materials in mixtures. Minimizing the superplasticizer dosage and, consequently, increasing the paste volume (by means of a higher limestone filler content) to keep adequate fresh properties is found to be the most effective optimization criteria to enhance the robustness of SCC mixtures.