Abstract:
Clays have a tendency to undergo volumetric changes on their interaction with water. Due to alternating cycles of wetting and drying all year long, these soils undergo fatigue and are a common cause for differential settlement of structures. These soils are a very common reason for most of the foundation failures due to their degraded properties like low shear strength, low bearing capacity, high shrink-swell potential and high compressibility. Expansive Soils present significant geotechnical and structural engineering challenges the world over, with costs associated with expansive behavior estimated to run into several billion annually. Engineering properties of these soils must be improved by chemical or mechanical means to meet structural requirements. This research deals with the use of Eggshell powder (ESP) as an admixture in treating expansive soils. Obtained changes in the plasticity, swell percent and strength parameters of treated and untreated samples were used as an indicator that Eggshell powder can be used as a stabilizing agent for expansive clayey soils, effectively. Properties of Soil from Nandi Pur (Gujranwala) and NUST Clay (made expansive by adding different percentages of bentonite by mass) were checked and then treated with increasing percentage of ESP by mass to compute the optimum feed for the additive. Eggshells are a waste material and are readily and cheaply available all around the world. Hence it would be both cost effective and environmental friendly. Treatment with Eggshell powder showed marked increase in Undrained Shear Strength, Cohesion and Angle of friction along with acceptable decrease in Plastic Limit, Liquid Limit and Swell Potential. These results are also compared with previously held research on similar admixtures to study the efficiency of ESP as additive.
