Optimal Design of Ecological Concrete Mix Proportion Based on AHP-GWO-BP Neural Network

Abstract

Ecological concrete has excellent water and air permeability, which not only is conducive to plant growth but also allows surface water to infiltrate underground and intercept pollutants. The performance of ecological concrete is largely determined by the nature of the raw materials and their relative content. Therefore, mastering the optimal design method for the mix proportion of ecological concrete is crucial to achieving good performance. In the current research, there is a lack of systematic intelligent decision-making models for predicting performance and optimizing mix proportions. In this paper, four factors, namely mechanical properties, water permeability, decontamination properties, and planting properties of ecological concrete, were considered when evaluating the comprehensive performance of ecological concrete. The evaluation was conducted using the analytic hierarchy process (AHP). The gray wolf optimizer (GWO) was introduced to enhance the backpropagation (BP) neural network, and an optimization model for finding the optimal ecological concrete mix proportion was established. The optimal mix proportion of two types of typical ecological concrete, one for filtration and one for plant growth, was discussed. The results indicate that the AHP-GWO-BP model calculates the optimal mixing proportion of filtration ecological concrete as follows: The diameter of coarse aggregate is 10–15 mm, with adsorbed coarse aggregate accounting for 49.7%, a component ratio is 118%, the water–cement ratio should be 28.7%, and the silica fume mix ratio should be 32.1%. According to the given parameters, the performance test of ecological concrete is conducted, with a coarse aggregate size of 12 mm. The results showed that under these parameters, the compressive strength was 12.3 MPa, the flexural strength was 3.35 MPa, the water permeability coefficient was 14.87 cm s⁻¹, the porosity was 27.23%, the removal rate of total nitrogen was 80.56%, the removal rate of total phosphorus was 67.33%, the pH was 9.16, and the plant dry weight was 9.37 g. The optimal mix proportion of the planting ecological concrete is as follows: The diameter of the coarse aggregate is 20–25 mm, the adsorbed coarse aggregate accounts for 49.7%, its component ratio is 138%, the water–cement ratio should be 27.3%, and the silica fume mix ratio should be 34.1%.