Enhancing Some Geotechnical Characteristics of Laterite Soils Using Limestone Ash Waste

Aims: The potential of limestone ash for the improvement of some geotechnical properties of Laterite soils for construction purposes was evaluated. The assessment involved the determination of the engineering properties of Laterite soil in its natural state as well as when mixed with varying proportions of limestone ash.

Study Design: Experimental study was employed to achieve the aim of the study. The experiment was conducted in the geotechnical laboratory.

Place and Duration of Study: The study was conducted at Nsukka in Enugu State, South-Eastern Nigeria. Fieldwork was carried out for a period of one month while the laboratory experiments were conducted over a period of five months from June to December 2013.

Methodology: Lateritic soil samples were obtained from freshly exposed gully cuts to a depth of 1.5 m in Enugu, Nigeria. The soil samples were air-dried for two weeks after which the following parameters were tested for: Atterberg limits, grain size analyses, compaction characteristics, California Bearing Ratio (CBR) and compressive strength. Natural moisture content of the soil was determined by placing 38 g of the sample in an oven for a period of 24 hours in which the moisture content was obtained by subtracting the weight of the of dry soil from the weight of the wet soil and the container, multiplied by 100%. The geotechnical properties of the soil were determined both in the natural state and after stabilisation with varying percentages of limestone ash waste at a normal curing of 6 hours. Accelerated curing at 40°C, 60°C and 80°C for 24 hours was carried out for compressive strength tests for 4% and 6% respectively due to similarities in the values of both the CBR and compressive strength.

Results: The dry density and plasticity index decreased while liquid limit, plastic limit, compressive strength and CBR increased with increasing percentages of limestone ash. Maximum strength was achieved at 6% proportion of limestone ash for CBR and compressive strength respectively.

Conclusion: The results of this research indicate that limestone ash is comparatively suitable for the chemical stabilisation of Laterite soils as lime is, as reported by other researchers.