Enhancing sedimentary rock properties using castor oil-based polyurethane grouts

Abstract

The use of polyurethane grout (PUG) has recently grown in popularity as a quick and efficient method for filling cavities and cracks in rocks. Fractured limestone rock masses are subjected to collapse and instability, causing important geotechnical challenges. This study aims to investigate the use of an eco-friendly, castor oil-based polyurethane grout (CO-PUG), with varying castor oil ratios (0–80 % by weight), as a sustainable alternative for treating limestone rock masses. The materials used in this study include castor oil, polyurethane, and limestone. The chemical structure and morphology of CO-PUG were measured utilizing FTIR and SEM, respectively. The density, permeability, and unconfined compressive strength of CO-PUG were assessed. Also, a direct shear test was performed on both the CO-PUG and on CO-PUG combined with limestone. The findings showed that CO-PUG closed-cell structure substantially reduces water absorption, resulting in a low permeability coefficient (K= m/s), as confirmed by the SEM study. The compressive strength of CO-PUG80 increased by 734.62 %, compared to PUG. Cohesion values increased with the percentage of castor oil increased, with the CO-PUG80 and CO–PUG80–limestone interface showing the highest values of angle of shear resistance at 47.35° and 55.87°, respectively. Based on these results, CO-PUG shows promise for the treatment of limestone rock mass, especially when used with a high castor oil amount. Also, the study showed the potential advantages of CO-PUG as an environmentally friendly material.