Behaviour and modelling of concrete incorporating agro-industrial wastes as a potential substitute for cement

Sustainable construction materials are one of the major solutions to combat climate change and reduce its impact on the global economy. This research study aimed to optimise the quaternary blend of cement, fly ash, pumice and rice husk ash using factorial experiments and elastic modulus tests, followed by their empirical modelling. Keeping the quantities of fly ash and rice husk ash per unit volume of concrete constant, it was observed that the compressive strength decreased with the increase in quantity of pumice per unit volume of concrete due to its lower specific surface area. Similarly, the highest value of elastic modulus was observed for the sample containing 10% fly ash, 15% rice husk ash, and 5% pumice, as it was approximately 14.2% and 13.9% higher than the control group at 28 days and 120 days, respectively. Novel equations for estimating elastic modulus and flexural strength as a function of compressive strength were developed and found to be statistically reliable. Lastly, in comparison to Random Forest model, the Extreme Gradient Boosting model successfully predicted the compressive strength of quaternary blended concrete as evident from its higher R² values of 0.999 and 0.921 and lower RMSE values of 0.419 and 4.96 during the training and testing phases, respectively, and the results were confirmed using the paired t-test.