Sand-Laterite Mixtures for Road Construction (A Laboratory Investigation)
Soil mixtures have been used extensively in developed countries to construct great lengths of road when other materials like cement and lime were not either available, developed or widely used. Developing countries with low per capita income, low cement and lime production, can use the same technique today. Laterite being readily available in many places can be mixed with sand to improve its strength, stability and other properties for this purpose. The paper sets out to investigate the improvements in the relevant properties of six samples of laterites when they are mixed with sand. The six samples are representative of the types of laterites occurring over the eastern parts of Nigeria. In practice, the mode of construction in which sand is used as a stabiliser instead of cement or lime could be used to minimise costs in the construction of roads carrying medium density traffic and in the surfacing of "unimproved roads". The results obtained show that for all types of laterites tested, the addition of sand to laterites has beneficial effects in reducing the liquid limit, the optimum moisture content, the plasticity index, the linear shrinkage and in increasing the maximum dry density and the California Bearing Ratio. There is an optimum sand percentage for maximising most of the parameters measured. This optimum sand percentage is different for each type of laterite and is also dependent on the level of compaction given to the mixture. Comparison of the results obtained with some specifications shows that the improvements obtained are such as would make the sand-laterite mixtures satisfy most specifications for the types of roads mentioned.