STABILIZATION OF EXPANSIVE SOIL WITH WASTE PLASTICS

Abstract

Expansive soils have high amounts of clay particles and have a special mineralogical characteristic. The presence of considerable amount of montmorillonite clay mineral causes them to swell and shrink when amount of water is changed. Due to successive shrink and swell, this type of soil causes some asphalt distresses like upheaval, roughness, rutting and longitudinal cracking. To other extent, black cotton soils in construction sites do have xiv xv significant influence on planning, structural design, construction & maintenance costs, performance and engineering life of roads. There are many techniques to improve poor engineering properties of expansive soils. One of this is stabilization of expansive soil with waste plastic materials in the form of flexi which was introduced in this specific study. The stabilization of black cotton soil with optimum amount of flexi material decreased plastic index (PI) value by 13.6% and optimum moisture content (OMC) value by 18.5%, increased maximum dry density (MDD) value by 1.9%, increased California bearing ratio (CBR) value by 50.9%, increased Cohesion(C) value by 83.3% and increased both unconfined compressive strength (qu) and un-drained shear strength (Su) value by 10.1%. The flexi material gave better strength and stability by means of replacement of black cotton soil by flexi. Sand also used as a stabilizer material to magnify the effect of flexi stabilizer. In addition, the correlation and regression model was done by the result of the laboratory test results of OMC, MDD, CBR, C, and qu as dependent variables with the independent variables of percent (%) of flexi and PI in a single regression analysis. A good correlation and regression models were developed between percent of flexi and CBR, qu & Su. Coefficient of determination (R2 = 0.79) indicates that CBR has strong relation with % of flexi by having equation of𝐶𝐵𝑅 = (2.9909) − (0.3465 ∗ % 𝑜𝑓𝑓𝑙𝑒𝑥𝑖)