Improving the Strength Characteristics of Red Clay Soil Using Waste Plastic Strips

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Addis Ababa University


Soil stabilization is the physical and chemical alteration of soils to enhance their physical properties. Stabilization can increase the shear strength of a soil and control the shrink-swell properties of a soil, thus improving the load-bearing capacity of a sub-grade to support pavements and foundations. Stabilization can be used to treat a wide range of sub-grade materials from expansive clays to granular materials. The cost of introducing traditionally available stabilizers has increased in recent years which opened the door widely for the development of other kinds of soil stabilizers such as plastics, bamboo etc. The research is basically conducted by waste plastic strip and red clay soil found in KecheneRas Desta road. The significance of the study is to provide alternative stabilization material in construction industry. The objective of this study is to improve the strength characteristics of soil using the stabilization of plastic strips. In this regard an attempt has been made to evaluate the effect of plastic strip as a stabilizer on the geotechnical properties of red clay soil in stabilized form mainly strength and compaction characteristics. The preliminary investigation of the soil to be stabilized shows that it belongs to A-7-5 class of soil in the AASHTO soil classification system. Soils under this class are generally of poor engineering use. Therefore, series of laboratory tests such as Atterberg limits, free swell index, compaction, UCS and soaked and unsoaked CBR tests for different percentages of plastic were performed. The soil was stabilized with plastic in stepped concentration of 0%, 0.5%, 1.5%, 2.5%, 3.5%, 5%, and 7.5% by dry weight of the soil. The analysis shows slight improvement on the geotechnical properties of plastic stabilized soil. The plastic strip is found to increase the unconfined compressive strength of the soil up to 5% of plastic (75.01 kPa to 196.14 kPa) and CBR result of the red clay soil up to 2.5% (soaked CBR from 3.5% to 5% and unsoaked CBR from 80.3% to 108.7%). Due to plastic’s light weight property the MDD of the soil shows slight increase up to 2.5% of plastic from 1.4g/cm3 to 1.53 g/cm3, and as the ratio of the plastic increased in the clay soil the result decreases.



Red clay Soil, Plastic strip, Soil stabilization, Atterberg limit, Compaction, UCS, CBR value