Effect of Polypropylene Fiber and Posidonia Oceanica Ash on the Behavior of Expansive Soils

ABSTRACT: This study presents an experimental study evaluating the effect of synthetic and natural additives on the behavior of an expansive soil from a local deposit. The synthetic additive used is polypropylene fiber which constitutes the major part of this research work. The initial phase of the experimental program includes the study of the effect of polypropylene fiber on maximum dry density and optimum moisture content with different fiber inclusions. Dynamic compaction tests have been conducted on an expansive soil sample with percentages of 0%, 0.5%, 0.75%, and 1% polypropylene fiber additions (by dry weight of the soil). The specimens used for volume change and strength tests were conducted on specimens prepared by static compaction at optimum water content and maximum dry density obtained by dynamic compaction of Standard Proctor procedure. The second phase of the experimental program focuses on the strength and volume change behavior of unreinforced and reinforced specimens. In the third phase, the effect of the polypropylene fiber on soil- water characteristic curve is studied. Finally it is concluded that mitigation of expansive soils using polypropylene fiber might be an effective method in enhancing the compression, tension and Air entry values of the subsoils on which roads and light buildings are constructed. The natural additive used in this study is abundantly found Posidonia oceanica (sea weed) which is carried and deposited at the shores all along the coastline of Cyprus. The weed is burnt and its ash is used to investigate the potential effect on physical properties and swell behavior of the expansive soil used in this study. Despite the difficulties encountered in representative specimen preparation due to random distribution of fiber filaments, it is observed that there is a future prospect in the use of this environmental friendly additive for soil mitigation. Keywords: polypropylene fiber, compressive strength, static compaction, dynamic compactions, Soil water characteristic curve. …………………………………………………………………………………………………………………………