Stabilization Of Weak Subgrade Soil Using Maize Cob Ash And Waste Brick Powder: A Case Study at Tarcha Zuriya Woreda

Abstract

Strength of weak soils present significant geotechnical, road pavements, and structural engineering challenges the world over, with costs associated with expansive behavior estimated to run into several billion dollars of damage annually. Expansive soils are soils that experience significant volume change (swelling and shrinking) associated with changes in water contents. These problems need a wider application of cost effective and environmentally friendly technology for improving soil properties to be adapted to the current road construction trend. The general objective of this research is to investigate the suitability of MCA and WBP for stabilization of Weak subgrade soils. To achieve the objectives of the research to based on the properties described under field investigations:- Four samples were taken from different locations. A free swell test, high plastic index and low load bearing were carried out for each sample, one sample with high free swell, high plastic index and poor soil values had been selected. Tests were performed on natural and treated soil samples as per the ERA, AASHTO, and ASTM laboratory test standards. The selected soil samples were characterized and were found A-7-5 category of soil based on the AASHTO soil classification system and CH as per the USCS soil classification system which is clay soil of poor engineering properties. The soils were treated with varied proportions of MCA (5%, 10%, 15%, and 20%) and WBP (10%, 20%, 30%, and 40%). and (5%MCA + 40 %WBP, 10%MCA + 30 %WBP, 15%MCA + 20 %WBP, 20%MCA + 10 %WBP ) by dry weight of the soil. The laboratory tests carried out to evaluate the stabilized soil sample were; Atterberg limits, free swell, compaction tests, and CBR tests. Analysis of the results shows that improvement on the engineering properties of MCA-WBP stabilized soil. As the MCA WBP content adds, reduces plasticity index and swelling potential, increase MDD and the OMC is decrease and the CBR strength also increased and the better improvement was found when using 10% MCA and 30%WBP. It can be concluded from the present investigation that weak subgrade soil could properly be treated for use as subgrade material. Adequate strength was achieved with 10% MCA mixed with 30%WBP, and which is found to be the optimum Maize cob ash and waste brick contents for improving the engineering properties of the weak subgrade soils.