Effects of cow dung ash and calcium hydroxide on geotechnical properties of expansive and loose soil

The study is an investigation into the effects of CDA and Ca (OH)2 on geotechnical properties of expansive (Sample A) and loose soil (Sample B). The experiments were designed to study the effects of adding CDA in various percentages by weight (5%, 15% and 15%) of dry soil with 5% constant Ca (OH)2, which produces pozzolanic reactions in soil samples.

Sample A was collected at Moniya, Ibadan, Sample B from The polytechnic, Ibadan and, cow dung was obtained from a farm settlement at Ilora, Oyo State, the dung was air dried and then calcined at 500 0C – 600 0C, after which it was sieved using 600µm sieve. The samples were subjected to the following laboratory tests; Natural moisture content, Particle (grain) size analysis, Atterberg limit test, Compaction test, California bearing ratio (CBR) test. The NMC test shows that sample A retains more water than sample B given by the values 26% and 6% respectively, the particle size analysis results showed that sample A has highest percentage of clay passing sieve no. 200 (75µm) i.e. 62.86%, while sample B has 7.27%, this indicates that sample A with high silt clay content are susceptible to volume changes when wet. The liquid limit and plasticity index for sample A is 49% and 28% respectively while sample B is a cohesionless soil. This shows that sample A has high clay content and its load bearing capacity could be reduced when wet. The AASHTO system classified sample A as A-7-6, and sample B as A-3. This shows sample A is fair to poor while sample B is excellent to good. The maximum dry densities ranged from 1.61mg/m3 to 1.87mg/m3 and Optimum moisture contents range from 19.2% to 16.36% respectively. The CBR value of sample A as to the varying percentage are 2.07%, 10.62% (0% CDA & 5% Ca(OH)2) , 12.69%, 16.77%, 31.41% while CBR value of sample B are thus: 32.7%, 27.06% (0% CDA & 5% Ca(OH)2), 12.09%, 16.2%, 16.74%. It was then observed that CDA at 15% and Ca(OH)2 at 5% is the optimum for expansive soils while adding CDA and Ca(OH)2 to loose soil will increase the OMC and thus reduce its engineering properties.