Optimization of Consistency Limits and Plasticity Index of Fine-grained Soils Modified with Polypropylene Fibers and Additive Materials

Abstract

It is a well-known fact that water content has a significant effect on the engineering properties of fine-grained soils. There is a close relationship between consistency limits and geotechnical parameters of fine-grained soils. This experimental study was performed to investigate the effect of randomly distributed polypropylene fibers (PP) and some additive materials {[}e.g., Borogypsum (BG), Fly Ash (FA) and Cement (C)] on consistency limits and plasticity index of a fine-grained soil. The Taguchi method was applied to the experiments and standard L9 Orthogonal Array (OA) with four factors and three levels were chosen. A series of consistency limits were conducted on each specimen. 0-20\% BG, 0-20\% FA, 0-0.25\% PP and 0-3\% of C by total dry weight of mixture were used in the preparation of specimens. In the tests, distilled water (DW), DW + 0.05\% Air-Entrainer (AE) and DW + 0.15\% AE were used as mixture liquid. Experimental results showed that the most effective material for decreasing the liquid limit and plasticity index of the samples were fly ash, polypropylene fiber respectively. The plasticity index decreased with increasing of AE. The values of plasticity index for distilled water, distilled water + 0.05\% air-entrainer and distilled water + 0.15\% air-entrainer in optimum conditions were 16\%, 14\% and 8\%, respectively.