Effect of Addition of Plastic Fibres on Strength Characteristics of Subgrade Soil

Abstract

In today’s time, plastic materials (which otherwise pose great threat to environment), can be alternatively and smartly utilized in civil engineering as a soil stabilizing material (apart from the more traditional cement and lime) to achieve economy and reduce waste impact on environment. In present study, effect of addition of plastic fibres (shredded wrappers) on the strength characteristics of flexible pavements have been studied. Available literature after been reviewed, and then experiments were performed to compute the liquid limit, plastic limit and plasticity index of soil to categorize type of soil. OMC (Optimum moisture content) and MDD (Maximum dry density) were computed at various plastic contents (by % of dry weight of soil). The CBR (California bearing ratio) test has been performed at different percentage plastic contents. The maximum value of CBR was obtained as 4.01% at 1.5% plastic content. The design of pavement section have been carried out for different traffic volumes to find the most efficient and economical traffic condition for which this method could be most advantageous. Thickness of pavement for each layer (as per CBR corresponding to 0 and 1.5% plastic content) was determined using IRC-37:2018 design plates. The theoretical values of vertical compressive and horizontal tensile strains at critical locations have been determined. The theoretical value of modulus of elasticity (with 0 and 1.5% optimum plastic addition) were calculated using IRC 37:2018. Trial sections filled with virgin soil and reinforced soil at various percentages of waste plastic content were compacted manually to 250 mm thickness and the subgrade modulus were determined experimentally by using a Light Weight Deflectometer. The theoretical and experimental modulus values were compared, and the most optimized pavement thickness has been designed with IIT PAVE.