Effects of partial replacement of lime with burnt clay brick powder on physical and mechanical properties of black cotton soil

Abstract

Black cotton soil is an expansive soil, it expands when wet and shrinks when dry causing cracks which on re-wetting, bulks out and causes damage to structures built on them, hence requiring the use of stabilizing agents to improve the soil engineering properties. Traditional stabilizers like cement, lime and others have been efficient and effective in soil stabilization but their rising cost and negative impact to the environment has led to research into waste crush burnt clay brick (brick powder) to be used as an alternative in soil stabilization. The aim of the study was to determine the effect of partial replacement of lime with burnt clay brick powder on physical and mechanical properties of the BCS to be used for road construction in Uganda. The study investigated the properties of natural BCS and when stabilized by lime at 2% plus incremental percentages of brick powder from 5% to 20%. First, particles size distribution was determined from grading test (wet sieving and hydrometer soil analysis), secondly varied percentages (0% to 4%) of lime were used to stabilize clay soil and PI and CBR were determined. The same procedure was repeated for 2% lime combined with varied percentages of brick powder (0% to 20%) on the sample. The PI decreased with increase in lime content from 29% to 12% and for lime partially replaced with BP also decreased from 25% to 12%. The CBR increased from 4% to 28% and 10% to 22% for lime and lime partially replaced with brick powder respectively. The combination of lime and brick powder gave good results that met the set standard by road design Manual part III of Minimum CBR of 15 for subgrade of road at 15% brick powder with a value of 22 at 95% compaction. When lime and brick powder were combined at the optimum ratio of 2:15, the stabilization results of California Bearing Ratio of 22, Plasticity index of 15, Linear shrinkage of 7.28, 0.13 CBR swelling create a material that can be used for construction works. Therefore, the study shows that lime in combination with brick powder can be effectively used to improve BCS. It is therefore, recommended that since brick powder can partially replace lime in clay stabilization to form material with cementitious properties, the use of lime should be minimized to reduced creation of carbon footprint in the environment.