Compaction characteristics and strength of BC soil reinforced with untreated and treated coir fibers

Black cotton soils, because of its high swelling and shrinkage characteristics, have been a challenge to geotechnical engineers. Use of natural reinforcing materials in soil such as jute and coir has the advantage that they are available at low cost. Among the natural reinforcing fibers in soil, coir has the greatest tensile strength and retains its property even in wet conditions and has been used in many non-critical civil engineering applications. In the present study, compaction characteristics of black cotton soil (BC soil) admixed at different percentage of untreated and treated coir fibers were used with optimum lime content and without lime content. Alkali-treated and epoxy resin-coated and stone dust-sprinkled coir fibers have been comparatively assessed in terms of compaction characteristics and strength of fiber-reinforced BC soil. The present study indicated that the maximum dry density decreases with increase in percentage of coir fibers for both black cotton soils with and without optimum lime content. Marginal variation in maximum dry density (MDD) when fiber content is varied from 0 to 0.5% occurs and beyond 0.5% fiber content significant reduction in MDD occurs. Increasing fiber content increases the corresponding optimum moisture content (OMC) indicating addition of fiber increases water absorption by coir fibers causing an increase in OMC. However, the alkali treatment of coir fiber causes a significant reduction in water absorption leading to significant improvement in compaction characteristics and strength of BC soil.