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|Title: ||Improvement of naturally-occurring materials for road construction in the Kumasi Metropolis, Ghana|
|Authors: ||Frempong, Eric M.|
|Issue Date: ||29-Jul-1997|
|Series/Report no.: ||2562;|
|Abstract: ||In some parts of Ghana road construction costs could be very high because of the limited opportunity of locating suitable base material within economic haul distances.
This study was undertaken to improve sub- standard but abundant naturally - occurring materials within the Kumasi metropolis for use in road construction. Five soils typical of the soils within the Kumasi metropolis (e.g. sandy clayey quartzitic or lateritic gravel, clayey sandy quartzitic or lateritic gravel, micaceous silty sandy gravel, silty sandy gravel, silty gravelly sand) were studied. These were designated MP-l, MP-2, MP-3, MP-4 and MP-5. In their untreated form these soils do not satisfy the specification requirements for use as road base material. Changes in engineering properties due to the stabilisation of these soils with varying proportions of Rock Aggregates, River Gravel, Quarry Dust, lime and the blending of the other soils with MP-3 were investigated. Economic analysis of the use of these stabilisers was also made.
The results of these improvement studies indicated the River Gravel to be the most effective in improving the particle size distribution of the soils. The improvement in plasticity of the soils varied with the type and content of stabiliser used. Lime had the most pronounced effect with respect to reducing plasticity; with only 2% lime the plasticity indices were reduced by 48 - 60%.
The improvement in strength also varied with the soil type and stabiliser. The proportion of Quarry Dust needed to improve the strengths of the clayey sandy quartzitic gravel (MP-l) and the sandy clayey lateritic gravel (MP-3) to base material quality ranged from 10% to 15% and 20% to 30% respectively. The studies have also shown that the 96 - hour soaked California Bearing Ratio (CBR) value of at least 80% which is required for base material could be achieved for most of the stabilised soils. Rock Aggregates, Quarry Dust and, to a lesser extent, River Gravel were more efficient for strength improvements of all the soils than for the reduction of plasticity. However, lime was more efficient for strength improvements as well as the reduction of plasticity and swell characteristics of all the soils. The amount of lime required to ensure the optimum modification of any of the soils to enhance its workability, lime modification optima, was either higher than or equal to that for strength optimisation.
Quarry Dust was the cheapest effective stabiliser while lime was the most expensive. The cost of incorporating 2% lime was generally equivalent to the cost of hauling suitable material from a borrow pit located at almost 10km from the project site.
The results of the economic analysis have also shown that, beyond 16km, it would be uneconomical to haul gravel for road construction in the metropolis. Rather, Quarry Dust, River Gravel and Rock Aggregates, should in the decreasing order of preference, be used to stabilise abundant naturally - occurring materials for an economic and durable base course construction.|
|Description: ||A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Philosophy, 1997|
|Appears in Collections:||College of Engineering|
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