Cost and Time Effect of Using Sub Grade ANSS Chemical Stabilizer on Road Construction (A Case Study of Addis Ababa City, Road Construction on Expansive Soil)

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Addis Ababa University


Road connectivity is one of the key components for development in a city as well as in a nation, as it promotes access to economic and social services, generating increased income and employment. However, the construction of such economically vital sector is the most expensive and time taking public project undertaken by the government. Conventional pavement design and construction practices require high quality materials to fulfill minimum construction standards which will be transported from long distances from the project site under construction which is costly. In addition, natural resources are degraded and environmentally affecting the quarry areas which has significant environmental effect, and this way of construction takes longer time to complete the project. In many of road projects it is very difficult to obtain suitable construction materials for sub grade with in economical hauling distances. One of the proven technologies to reduce cost and time of road construction is enabling use of marginal materials by using stabilization of soil. Stabilization can be derived from chemical, electrical, mechanical or thermal means. In this study chemical stabilizer are considered. Chemical stabilizers can generally be categorized in to two broad categories: conventional and unconventional stabilizers. Conventional stabilizers such as cement lime, fly ash, and bituminous products have been intensely researched, and their fundamental stabilization mechanisms have been identified. Unconventional soil stabilizers are additives consist of a variety of chemical agents that are diverse in their composition and in the way they interact with the soil. In this research ANSS (Anyway Natural Soil Stabilizer) which is categorized as unconventional chemical stabilizers used to analyze the effect of stabilizer on engineering properties of expansive soils. A case study has been made on Addis Ababa City roads which are constructed on expansive soils are taken. In the laboratory, the native soil were combined with different dosages of the stabilizer 2%,4%, 6% and 8% to find out the optimum dosage of stabilizer. From the laboratory test results it is confirmed that 6%is an optimum dosage of stabilizer for the typical expansive soil in the study area. Using this optimum dosage of chemical stabilizer cost and time comparison have been made with the conventional way of construction. xv As it has been observed from the analysis, treated expansive soil with 6% of the chemical stabilizer improves the bearing capacity and Plasticity of the soil to a required level and it saves around 30% of the cost and 42% of the time of road construction in a the city which is constructed in a conventional way, however the performance duration of the stabilizer shall be studied further in the future, as the road which have been done with same technology shall be evaluated after some service years.



Geotechnical Engineering