ABSTRACT
Due to the economic meltdown which has immensely affected road construction in Nigeria and other developing countries the use of cement, asphalt, additives and other conventional materials to stabilize sub base and sub grade of pavement, is far from being cost effective, therefore 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. Laboratory tests such as Bulk density test, moisture content test, specific gravity test, sieve analysis test, compaction and California Bearing Ratio test (CBR) were carried out on the control sample (natural soil). The natural soil was stabilized with cement in various percentages (2%, 4%, 6%, 8% and 10% respectively). The natural soil was also mechanically stabilized with quarry dust and sharp sand in varying percentages; (15%, 30%, 45%, 60% and 75%) for quarry dust, and (20%, 40%, 60%, 80% and 100%) for sharp sand. Compaction tests and California bearing ratio tests were carried on these stabilized soils for the purpose of strength comparison and evaluation of the suitability as sub base material.
For the control sample, the result of the average specific gravity was obtained to be 2.46. The liquid limit was obtained as 33.00%, plastic limit as 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. This value indicates that is good for subgrade material. The OMC and MDD were 12.2% and 1.76g/cm3 respectively. And the maximum value for soaked CBR was obtained as 15.69%. When the natural soil was reinforced with cement, 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 35.48% to 73.74%. When the soil was reinforced with quarry dust, 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 reinforced with sharp sand, 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 5.87% 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.
