Multi-objective optimization of coal waste recycling in concrete using response surface methodology

Coal waste application in concrete is an appropriate alternative to recycle mining waste and reduce their environmental problems as well as produce concrete with acceptable mechanical properties. This research aims at determining the optimal mix proportion of concrete mixtures produced with coal waste in terms of both waste recycling and two mechanical properties. For this purpose, the effect of four independent variables of water to cement ratio (W/C), cement content, gravel volume, and coal waste on the two response variables of concrete compressive strength and water absorption percentage was experimentally investigated. A combination of response surface methodology (RSM) and desirability function method was applied for modeling the relation of independent and response variables and multi-objective optimization of six optimization scenarios. Results showed that the best optimization scenario in terms of waste recycling and concrete production is to maximize coal waste and compressive strength as well as to minimize concrete water absorption. For this scenario, the optimum value of W/C, cement content, gravel volume, and coal waste is 0.44, 304 kg/m(3), 954 kg/m(3), and 36.95 kg/m(3), respectively, and concrete compressive strength and water absorption at this condition is about 46.30 MPa and 7.41%, respectively. The results of this study as a step towards sustainability provide researchers with new insights about finding the most efficient condition in terms of both waste recycling and concrete production.