Improvement of Unconfined Compressive Strength of Clayey Soil using Paper Pulp

Abstract

The soil in Islamabad, and particularly Bahria Town, is predominantly earth-filled and is subject to clayey characteristics. It has shown tendencies of low strength under load which poses a unique problem and jeopardizes the construction process. This project aims to provide an economically and environmentally feasible utilization of paper pulp in the improvement of the unconfined compressive strength of predominantly clayey soil. Samples were collected from Bahria Town Islamabad and laboratory testing was done to determining soil index properties. These included the Particle Size Analysis, Atterberg Limits, and Specific Gravity tests. The results obtained from the laboratory tests were used to classify the soil by USCS classification as low plasticity clay (CL) with sand. The Standard Compaction test was performed to obtain the maximum dry density and the corresponding optimum moisture content which were 1.83 g/cm3 and 15% respectively. The unconfined compression test (UCT) test was then performed using the MDD of this soil with natural soil which gave the unconfined compressive strength of 134 kPa. Then the natural soil was treated with paper pulp additive with increments of 2% up to 8%. The unconfined compressive strength at different percentages of paper pulp was plotted which gave a parabolic curve with peak strength improvement at 6%. The Unconfined compressive strength at 6% additive was 296.1 kPa. There is a 120% increase in strength while the average increase in strength is about 55% at 4% and 8% content of additive. As depicted by the graph plotted by the UCT 6% paper pulp mixed with soil bore the maximum strength, therefore it is considered to be the optimum content of paper pulp as an additive. Moreover, the addition of the pulp induced no compromise in strength whatsoever.