Utilization of Waste Agricultural Products Soybean Pod Ash and Banana Fiber to Enhance Expansive Soil

Abstract

Expansive soil is challenging for civil engineers due to its swelling and shrinking nature in wet and dry conditions. Damage to shallow foundations like pavement and the footing of residential houses occurred due to these soils. The annual damage due to the expansive soils will probably reach more than $1 billion in the United States. In Ethiopia, expansive soils are estimated to cover 40% of the country. Different scholars deal with stabilizing expansive soils by using different mechanisms. This study also evaluated the utilization of waste agriculture products soybean pod ash (SBPA) and banana fiber (BF) to enhance the expansive soil properties found in Jimma town. To accomplish this study, purposive sampling techniques were adopted. This expansive soil sample was collected from two test pits in Jimma town (Kebele 5 and Ajip Kela locations) at a depth of 1.50m. From those samples, the smallest CBR values and the highest plasticity index were taken for further analysis. Soybean pod samples and banana fiber were collected based on desired content from the local area of the Jimma Zone around Sarbo. The various geotechnical parameters were determined for natural soil and mechanically stabilized by various proportions of soybean pod ash in natural soil. Then, after treating the natural soil with varying percentages of soybean pod ash (3%, 6%, 9%, 12%, and 15%), afresh natural soil is treated with a length of 15mm and varying percentages of banana fiber (0.25%, 0.5%, 0.75%, 1%, and 1.25%). The fiber is not treated with any chemicals. Then (3% SBPA+0.25% BF, 6% SBPA+0.5% BF, 9% SBPA+0.75% BF, 12% SBPA+1% BF, and 15% SBPA+1.25% BF) of soybean pod ash and banana fiber, respectively, were combined with natural soil. From the sieve analysis tests, the percentage of Ajip Kale passing through sieve No. 200 (0.075mm sieve size) was 97.34%, and Kebele-5, 95.9%. This result shows that the samples are highly clayey. The natural soil samples are classified as A-7-5 according to the AASHTO soil classification system and CH according to USCS. As it was observed from the CBR test result, when SBPA and BF content increase, the CBR value also increases until 9% SBPA and 0.75% BF content are added, and then decreases. So, 9% SBPA and 0.75% BF contents can be taken as optimum content to produce the best combination, which improves the performance of expansive soil. Also, it was observed that banana fiber and soybean pod ash increase the UCS value of expansive soil, and great improvements were found when using 9% SBPA and 0.75% BF. From the compaction test, it was observed that as SBPA and BF content increased, MDD decreased, and OMC increased for the sample. MDD decreases from 1.38 g/cm3 to 1.29 g/cm3, and again, OMC increases from 26.8% to 31.8%. Therefore, it was concluded that utilization of waste agricultural products Soybean pod ash, and banana fiber is applicable for expansive soil stabilization to enhance the engineering properties of expansive soils and is economically and environmentally friendly.