Effect Of Mixture Of Corncob Ash And Lime On The Engineering Properties Of Black Cotton Soil Found In Jimma City.

Abstract

Many of the soils of Ethiopia are covered by expansive soil, and are difficult to use in the construction of highways and airfields because of their high content of plastic clay and their expansive tendencies. The existence of expansive soil in Jimma area has caused damage to the light building, asphalt pavement, and buried utility lines. Several methods have been developed successfully to use pozzolanic materials such as Portland cement, lime, fly-ash, bitumen, and polymers for high strength concrete, soil improvement, and other civil engineering works. The over-dependence on the utilization of industrially manufactured soil-improving additives cement and lime has kept the cost of soil stabilization very high. These studies mainly focused on determining the effect of the mixture of corncob ash with lime on the Engineering properties of black cotton(BC) soil. Due to different soil problems, searching for the best soil stabilizer to overcome problems that occur by the BC soils is still being the main concern to achieve the required soil engineering properties. In order to address the aforementioned purposes, two subgrade soils were collected from Jimma City around Mendera Kochi( Green Sefer) and Merkato Sefer around the Police station. The soil samples collected from a local area within a depth of 1.5-2m. The laboratory tests which were carried out Moisture content, Specific Gravity, Grain size Analysis, Liquid limit test, plastic limit, plasticity index, permeability, UCS, CBR, swelling index, compaction, XRF and XRD. The samples tested on black cotton clay, black cotton clay+ % corncob ash, Black cotton clay + % corncob ash + % lime using different apparatus as per the procedures laid down in American standard of testing materials and Ethiopian road authority manuals. The data processing and analyzing techniques used were both descriptive and analytical methods. The test results indicated that the Natural sub-grade soils are A-7-5 as per the AASHTO soil classification system and CH as per USCS. As far as the engineering properties of natural subgrade soils were studied, the two soils were highly Swelling clay soils. The two soils have almost similar Engineering properties. Sample-1 has PI of 66.28 %, FSI of 100%, CBR of 1.24%, MDD of 1.54% and OMC of 24.5%. Likewise, Sample-2 also has PI of 66.58 %, FSI 87%, CBR of 1.54%, MDD of 1.57%, and OMC of 24%, and both samples Categorize as Illite, and smecitite minerollogically. As the amount of Lime ratio increases LL, PI, OMC, FSI, CBR swell decreased whereas PL, MDD, CBR are increased, rather than Corncob ash alone. But the amount of Lime decreasing with increasing CCA ash beyond 2% the results were decreased as the respective test. For this study, 2% CCA + 6% LIME was found out to be the optimum ratio which achieved by most of the geotechnical parameters in the study. The XRD results indicated a general reduction in peak intensities in all clay minerals that are present in the soil and, most significantly, in montmorillonite. Finally, Microscopic Analysis using SEM & EDX should be taken to show the presence of C-S-H & C-S-A-H in both CCA and Lime treated clay soils.