The optimization of pervious concrete ratios with spontaneous combustion gangue aggregates based on the RSM-BBD method

In order to optimize the ratio of pervious concrete with spontaneous combustion coal gangue aggregate, 17 groups of experiments were designed by the BBD response surface method to study the effects of aggregate-cement ratio, water-cement ratio, and reinforcing agent on the compressive strength, permeability coefficient, and porosity of pervious concrete. The response surface model was constructed to reveal the correlation between various factors and response values and obtain the optimal ratio of comprehensive performance. The results show that each factor and each response value are quadratic polynomial models, and the regression coefficient R² of each model is greater than 0.9, indicating that the model is reasonable and fitting. The influence of water-cement ratio and aggregate-cement ratio on each response value and reinforcing agent on compressive strength is very significant. The influence of the interaction of aggregate-cement ratio and water-cement ratio on compressive strength and the interaction of water-cement ratio and reinforcing agent on porosity is significant. When the ratio of aggregate-cement ratio is 3.2, the ratio of water-cement ratio is 0.22, and the dosage of the reinforcing agent is 4.5 %, the 28 d compressive strength of pervious concrete reaches 28.7 MPa, the permeability coefficient is 3.21 mm/s, and the porosity is 19.7 %, which meets the engineering requirements of C20 pervious concrete.