Strength Comparative Analysis of Mechanical and Cement Stabilized Laterite Soil Used as Sub-Base in Pavement Construction

Abstract

The use of cement, asphalt, additives, and other conventional materials to stabilize the sub base and sub grade of pavement is far from being cost-effective due to the economic crisis, which has severely affected road construction in Nigeria and other developing countries. Hence this research: Strength Comparative Analysis of Mechanical and Cement Stabilized Laterite Soil used as Sub-Base in Pavement Construction. Soil samples were obtained from University of Benin burrow pit. Index properties and strength tests were carried out on the soil samples, while the strength tests were carried out on the stabilized soils for the purpose of strength comparison and evaluation of the suitability as sub base material. For the soil samples alone, the average results obtained for the specific gravity was 2.46; the liquid limit was 33.00%; plastic limit was 19.21% and plasticity index was 13.79% which indicates that the soil is of medium plasticity. From the sieve analysis, the soil was classified as an A-2-6 soil according to AASTHO (American Association of State Highway and Transportation) system of classification. The Optimum Moisture Content (OMC) and the Maximum Dry Density (MDD) were 12.2% and 1.76g/cm³ respectively. The maximum value for soaked CBR was obtained as 15.69%. When the natural soil was stabilized with cement at different percentages from 2 – 10 %, the OMC ranged from 12.6% to 14.6%, the MDD ranged from 1.72g/cm³ to 1.76g/cm³ and from the CBR tests, the value for the soaked CBR ranged from 24.21% to 73.74%. When the soil was stabilized with quarry dust at percentages ranging from 15% - 75%, the OMC ranged from 9.6% to 12.8%, the MDD ranged from 1.73g/cm³ to 1.81g/cm³ and from the CBR tests, the value for the soaked CBR ranged from 3.32% to 3.71%. The optimum mix proportion was obtained as 75%. When the soil was stabilized with sharp sand at percentages from 20% - 100%, the OMC ranged from 11.00% to 12.8%, the MDD ranged from 1.73g/cm³ to 1.78g/cm³ and the CBR tests, the value for the soaked CBR ranged from 5.70% to 9.21%. The optimum mix proportion was obtained as 80%. Soil stabilization techniques with cement at percentages 6%,8% and 10% gave CBR values that met the requirements of a good subbase course of a pavement or road in accordance with the Federal Ministry of Works and Housing specification. Quarry dust and Sharp sand, did not meet the requirements, hence not suitable for a subbase course. They can be used to construct local roads to be more stable and they can also be suitable with the addition of cement or other effective binders