Evaluating the Use of Polypropylene Polymer in Enhancing the Properties of Swelling Clayey Soil

Previous studies found considerable gaps in the knowledge concerning soil stabilization using polypropylene (PP) fiber polymer. Polymer stabilization is considered a recent method used to enhance the mechanical behavior of shrink-swell soils. This research illustrates the effect of adding Polypropylene polymer (PP) on the behavior of the prepared expansive soil through laboratory experiments using different percentages of the intended fiber polymer. Natural soil (from Al-Radhwaniah City) was mixed with 30% by mass of artificial bentonite to prepare an expansive soil sample, and this sample was treated by reinforcing it homogenously with the PP polymer. Laboratory experiments were performed to demonstrate that the PP polymer had a significant effect on the improvement of expansive soils. Five different percentages (0.4, 0.8, 1.2, 2, and 4% to the natural soil sample) of the PP polymer were used, and two different curing periods (3 and 18 days) were considered. The liquid limit, plasticity index, swelling potential, maximum dry density, and the unconfined compressive strength increased by using 0.4% and 0.8% of PP polymer and continued to increase with curing (3 and 18 days). On the contrary, a significant reduction in these values occurred when increasing the percentages of the PP polymer (1.2, 2, and 4%). Treated soil samples had a considerably reduced swelling potential, which dropped from 19.2% (of prepared soil) to 1.01% (for prepared soil + 4% PP polymer and the sample left for 18 days as a curing time).