Optimisation of mix design of concrete paving block using response surface methodology

Abstract

This study investigated the optimal water/binder (w/b) and aggregate/binder (a/b) ratios in producing a concrete paving block. The w/b and a/b ratios in the concrete paving block were optimised using the response surface methodology (RSM), considering the performances of the ultrasonic pulse velocity (UPV), flexural, and compressive strengths. Regression modelling was conducted to represent the relationships between the UPV and compressive strength and the compressive and flexural strengths. Generally, the UPV, flexural, and compressive strengths increased with the increment of w/b ratio and reduction of a/b ratio. The RSM suggested optimal ratios of 0.35 for w/b and 3.50 for a/b, that the paving block could exhibit UPV, flexural, and compressive strengths of 4.11 km/s, 4.13 MPa, and 33.2 MPa, respectively. The predicted values from the RSM varied less than 6% compared to the experimental values. The polynomial regression model could effectively represent the relationship between the UPV and the compressive strength and the relationship between the compressive and flexural strengths of the concrete paving block.