Uses of central composite design and surface response to evaluate the influence of constituent materials on fresh and hardened properties of self-compacting concrete

This research presents the details of an investigation carried out to study the effect of the addition of constituent material parameters on the fresh and hardened state properties of self-compacting concrete using a central composite design approach combined with response surface methodology. Self-Compacting Concrete (SCC) mixtures were made with the addition cement, coarse aggregate, sand, fly ash and super plasticizer in various proportions and their fresh state properties (J-ring, segregation resistance and V-funnel) and hardened properties (compressive strength at 28 days and modulus of elasticity) were measured. Results were analysed using a statistical model that was able to predict the effect of the independent variables on the responses by using multiple regression analysis. The coupled effect of the responses was carried out. An analysis of variance was used to determine the adequacy between the model and experimental values. It was concluded that models of a full quadratic can be used to evaluate the influence of constituent materials on the properties of SCC. All the mixtures developed exhibited fresh state property values which were within the range permitted in the SCC guidelines. Optimizations of the responses were done by using response surface methodology. It was concluded that the fresh properties cited were 18.3 seconds V-funnel, 849 mm J-ring flow, and 17.8% segregation resistance and the hardened properties were 35.254 to 48.174 MPa of the compressive strength and 27.214 to 39.026 MPa for the modulus of elasticity.