Optimization of Concrete Containing Polyethylene Terephthalate Powder and Rice Husk Ash Using Response Surface Methodology

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The continuous increase in population, advancement in technology, and affluence have influenced the amount of biodegradable and nonbiodegradable waste generated. Studies have shown that the utilization of different wastes in concrete is imperative to reduce the long-term environmental problems associated with their handling and management. This study evaluates the performance of concrete incorporating polyethene terephthalate powder (PETp) and rice husk ash (RHA) as supplementary cementitious materials varied at 0%, 7.5%, and 15%. Results indicated that the presence of PETp reduces workability while increasing the content of both PETp and RHA decreased the compressive and flexural strengths. A few studies have demonstrated the prediction and optimization of PETp as a fine aggregate. This study explores the central composite design of response surface methodology in optimizing the fresh and hardened properties of concrete incorporating PETp and RHA. The results indicate that workable concrete can be achieved with an RHA content higher than the PETp content. The analysis of variance provided effective models with good prediction capabilities. The simulated values from the models were close to those obtained experimentally. An optimal percentage of 5.76% PETp and 9.45% RHA was obtained for predicted responses and validated with a good level of accuracy. An overview of the different combinations of RHA and PETp indicates that concrete incorporating only RHA had the tendency to absorb the least water and exhibit low voids. However, the combination of 7.5% RHA and 7.5% PETp had a reduced water absorption when compared with a concrete mix containing 15% of either supplementary cementitious material. In general, eco-friendly concrete with improved durability can be produced by incorporating PETp and RHA.