An investigation into the effects of lime on compressive and shear strength characteristics of fiber-reinforced clays

To meet the ever-increasing construction demands around the world during recent years, reinforcement and stabilization methods have been widely used by geotechnical engineers to improve the performances and behavior of fine-grained soils. Although lime stabilization increases the compressive strength of soils, it reduces the soil ductility at the same time. Recent research shows that random fiber inclusion modifies the brittleness of soils. In the current research, the effects of lime and polypropylene (PP) fiber additions on such characteristics as compressive and shear strengths, failure strain, secant modulus of elasticity (E₅₀) and shear strength parameters of mixtures were investigated. Kaolinite was treated with 1%, 3% and 5% lime by dry weight of soil and reinforced with 0.1% monovalent PP fibers with the length of 6 mm. Samples were prepared at optimum conditions and cured at 35 °C for 1 d, 7 d and 28 d at 90% relative humidity and subsequently subjected to uniaxial and triaxial compression tests (UCT and TCT) under cell pressures of 25 kPa, 50 kPa and 100 kPa. Results showed that inclusion of random PP fibers to clay–lime mixtures increases both compressive and shear strengths as well as the ductility. Lime content and curing period were found to be the most influential factors. Scanning electron microscopy (SEM) analysis showed that lime addition and the formation of cementitious compounds bind soil particles and increase soil/fiber interactions at interface, leading to enhanced shear strength. The more ductile the stabilized and reinforced composition, the less the cracks in roads and waste landfill covers.