Evaluation of the strength characteristics of compacted clay soil stabilized with bio-enzymes

Abstract

Bio-enzymes are organic degradable materials, currently introduced as soil improvement additives. This paper evaluated the strength and compaction characteristics of selected clay soils using Urease bio-enzymes. The soils were stabilized with 5, 10, 15 and 20 % by weight of urease (bio-enzymes). The liquid limits obtained were 41 % and 50.50 %, Plastic Limit 28.08 % and 35.86 %, Plasticity index was 12.92 % and 14.64 % for samples A (A76) and B (A75) respectively. The moisture content and specific gravity for samples A and B obtained were 16.9 and 21.6 % and 2.79 and 2.75 % respectively. The compaction tests results showed that the optimum moisture content (OMC) decreases from 12.60 to 9.60 % with an increase in enzyme percentage from 0 to 20 % for sample A while the same decreases were observed for sample B from 17.20 % to 14.00 %. In addition, the work revealed a 116.98 % increment in California bearing ratio (CBR) value of stabilized soil (improvement) from 20.79 to 45.11 % for A-7-6 clay and 315.41 % increment in CBR value, from 10.06 to 41.79 % for A-7-5 clay when both samples were cured for 28 days with 0 to 20 % urease. After 28 days curing, there was 150 -175 % increment in unconfined compressive strength (UCS) of A-7-6 with 5-20 % of urease. Similarly, a 125 -156 % increment in UCS of A-7-5 soil was recorded with 5 -20 % urease. Bio-enzymes is therefore recommended as stabilizing agents for use in road or other constructions, especially where weak clay soils are encountered.