Effects of polypropylene fiber inclusion on the strength and volume change characteristics of cement-fly ash stabilized clay soil

ABSTRACT: An experimental investigation was conducted to evaluate the effects of polypropylene fiber inclusions on the geotechnical characteristics of a clayey soil that was chemically stabilized with cement and fly ash. For all stabilized soils, cement and fly ash were added at 8% and 30%, respectively. Reinforced stabilized soil specimens were prepared at four different percentages of fiber content (0.25%, 0.50%, 0.75%, 1.0%) and three different fiber lengths (6 mm, 12 mm, 20 mm). Unconfined compressive and split tensile strength tests were carried out after 7- and 28-day curing periods. The volume change characteristics of the reinforced stabilized soil were determined using shrinkage limit and crack reduction values. The interactions between the fiber surface and the stabilized soil were analyzed by means of scanning electron microscopy. According to the results, the compressive and especially the tensile strength values increased to a great extent following the addition of fiber into the stabilized soil. The highest strength values were obtained with 0.5–0.75% content for the 12 mm-long fibers. The shrinkage limit and crack reduction values increased with increased fiber content and greater fiber length, whereas volume changes decreased.