Mixture optimization of high-strength blended concrete using central composite design

Palm oil fuel ash (POFA) can be used as a supplementary cementitious material in concrete. In this study, micro and nano POFA were utilized as supplementary cementitious materials to produce high strength blended concrete. The effect of the binders on the fresh and hardened properties was investigated. Hence, the purpose of the study was to optimize the mixture proportions of high strength blended concrete with incorporated micro and nano POFA. The experiments were performed using Central Composite Design under the Response Surface Methodology. The results from the experimental program were used to validate the mathematical models developed from a statistical analysis of the responses. Based on the results, the model predictions were found to closely agree with the experimental data. The lack of a fit test and the high value of the coefficient of determination (R²) proved the adequacy of the regression model to predict the fresh and hardened properties of high strength blended concrete. An optimum mixture can be achieved with 10% micro POFA and 1.50–2.85% nano POFA which satisfies the optimization criteria.