Modeling compressive strength of Moroccan fly ash–phosphogypsum geopolymer bricks

Fly ash and phosphogypsum are industrial by-products requiring a cost to get rid of. Their potential use in the synthesis of geopolymer bricks provides great benefits such as the saving use of natural resources and the solid by-product waste management. Compressive strength is the most important parameter for geopolymer bricks design. In this study, two artificial neural networks, namely the multilayer perceptron (MLP) and the radial basis function (RBF) networks, have been investigated to predict the compressive strength. While developing the MLP or RBF models, 99 experimental observations were used for training and testing. Two evaluation steps were performed: The first step determined the effective number of hidden layers and neurons in each hidden layer as well as the appropriate activation function in predicting the compressive strength. The second evaluation step evaluated the accuracy with which the model would predict the compressive strength of geopolymers. The MLP neural network with two hidden layers having 8 and 10 neurons and the hyperbolic tangent activation function was the best model for predicting the compressive strength. Artificial neural networks can be used as a reliable and accurate technique for estimating the parameters of geopolymer materials.