Implementation of agro-industrial by-products in expansive soil amelioration: design of experiment approach

Abstract The utilization of waste residues for soil amelioration is becoming increasingly popular in the construction industry due to its potential for effective waste management and resource utilization. This practice is of utmost importance for the sustainable development of nations, as it offers both environmental protection and economic benefits. In this study, we investigate the sustainable incorporation of Design of Experiment (DOE) to optimize the use of binary additives for enhancing expansive soil. The selected binary additives for this study are calcium carbide residue (CCR) and palm oil fuel residue (POFR). A total of twenty different mix designs were prepared using various combinations of CCR, POFR, water, and soil, following the Scheffe’s DOE strategy. To evaluate the performance and effectiveness of the additives, mechanical testing, including durability and unconfined compressive strength tests, was conducted. The results showed peak values of 58% for durability and 735 kN/m 2 for unconfined compressive strength (UCS). Additionally, the analysis of variance and student t-test, which are standard techniques for assessing the goodness of fit, were applied to statistically analyse the mathematical models and validate their adequacy and validity. Microstructural experiments, involving scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), were performed on the natural soil and soil treated with the optimal level of additives. The SEM analysis confirmed the formation of new compounds resulting from the incorporation of CCR-POFR mixtures, while the FTIR analysis validated the presence of different molecular functional groups in the treated soil.