Prediction and optimization of the fresh and hardened properties of concrete containing rice hush ash and glass fiber using response surface methodology

Substantial efforts are being adopted worldwide for the proper utilization of waste materials and by-products as supplementary materials to produce sustainable concrete. Rice Husk Ash (RHA) and Glass Fiber (GF) are such materials that can contribute to improve the properties of cement concrete. This study aims at predicting and optimizing the fresh and hardened properties of concrete blended with RHA as cement replacement and GF as an additional reinforcing element using Response Surface Methodology (RSM). Volumetric percentages of RHA and GF were considered as two independent variables to develop probabilistic models for slump, fresh and dry density, compressive and splitting tensile strength as desired responses. The experiments were implemented using Central Composite Design (CCD) and a good correlation was perceived between the experimental and predicted values of responses. The effect of variables on the desired properties was investigated through Analysis of Variance (ANOVA) at 95 % confidence level. The results of lack of fit test and high values of coefficient of determination (R²) ranging from 0.9359 to 0.9975 indicate the adequacy of the probabilistic model to predict the responses of blended concrete. Finally, to validate the calculated models, experiments were performed with optimized proportions of RHA (16.05%) and GF (0.08%) and desired values of slump, fresh density, dry density, 28-day compressive strength and 28-day splitting tensile strength was obtained as 41.91 mm, 2469 kg/m³, 2402 kg/m³, 28 MPa, and 3.77 MPa, respectively. All the experimental values of the desired five responses were closely matched to the optimized values indicating the efficiency of RSM to evaluate the properties of blended concrete.