Experimental Study of the Effect of Polypropylene Fiber on Mechanical Properties of Lime and Cement Stabilized Soil

12 groups of soil samples were prepared with various percentage of PP-fiber content (i.e. 0.0%, 0.4%, 1%, 1.7% and 2.5% by weight of soil), cement (i.e. 0% and 4% by weight of soil) as well as lime (0% and 3% by weight of soil) to study the effect of PP-fiber on mechanical behaviour and strength of non-stabilized and stabilized clayey soil with cement and lime. The unconfined compression tests were carried out on samples that were cured at 30°C and kept for 14 and 28 days in oven. The test results showed that inclusion of fiber reinforcement in stabilized and non-stabilized clayey soil mixtures caused an increase in the unconfined compressive strength (UCS) and failure strain. However, such effects were much more evident in stabilized samples when compared with those of non-stabilized samples. Furthermore, maximum unconfined compressive strength of samples was obtained at an optimum percentage of fiber content of 0.4%. The results indicated that the existence of fiber in specimens decreased the stiffness of samples, caused more ductile behaviour and loss of post-peak strength. The interactions at the interface between fiber and soil matrix were studied by using Scanning Electron Microscopy (SEM). The results demonstrated that the friction and bound strength between fiber surface and soil were significantly effective in changing the mechanical behaviour of soil.