A study Stabilisation of Clay Subgrade Soil Using Periwinkle Shell Ash
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Date
2015
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Publisher
Obafemi Awolowo University
Abstract
This study determined the geotechnical properties of selected clay subgrade soils, and characterised the soils and periwinkle shell ash. It also determined the stabilising potential of blends of periwinkle shell ash, cement and lime on the geotechnical properties of the soil, as well as, the optimum periwinkle shell ash for stabilisation of clay subgrade soils. This was with a view to establishing the suitability and optimum content of periwinkle shell ash as a stabilizer of clayey subgrade soil for road construction.
Soil samples were collected from six different locations within Osun State, Southwest, Nigeria. Periwinkle shells were collected from a depot site at Ikorodu, Lagos State. The natural moisture contents of the samples as received, were determined using British Standard BS (1377) method, after which the samples were air dried in the laboratory at room temperature. The geotechnical properties [grain size distribution, liquid and plastic limits, specific gravity, compaction, California Bearing Ratio (CBR) and Unconfined Compression Strength (UCS)] of the soil samples were determined, using standard methods. The periwinkle shells were washed in water, sun-dried, fired inside a muffle furnace at 1000oC into ash form, and sieved through 0.425 mm sieve. The Periwinkle Shell Ash (PSA), were subsequently added to the soil samples in incremental values of 2, 4, 6, 8 and 10 percent by weight and the corresponding geotechnical properties were determined. Samples of the formulations were also stabilised using 2, 4, 6 and 8 percent by weight for lime and cement, and their effects on the geotechnical properties evaluated. The characterisations of the soil samples and the PSA were carried out using Fourier Transform Infrared (FTIR), Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDX) techniques. The optimum formulating mix was determined based on the plasticity and compaction characteristics of the stabilised soils.
The results obtained showed that the selected soils in their natural state belong to A-2-7 and A-7-5 soil classifications, with medium to high plasticity. The FTIR, SEM and EDX results showed that the clay samples are aluminosilicate with different aluminium, silicon and oxygen concentrations. The periwinkle shell ash has calcium and oxygen as its dominant component with traces of sodium and magnesium. The addition of PSA improved the plasticity index of the soil samples with the addition of 6 to 8 % giving the best result for the compaction and CBR. The 6 % PSA addition to the soil gave the optimum value for UCS of the samples. The mixture of lime and PSA in varying proportions also enhanced the plasticity index of the soils at 5 % lime and 4 % PSA mix, while 5 % lime and 8 % PSP improved the compaction characteristic and CBR values of the soils. For cement and PSA mix, 7 % cement and 6% PSA improved the plasticity index of the soils from 14.5 % to 9.2% and CBR value from 10.5 % to 38.44 %. Furthermore, the study showed that the geotechnical values obtained by adding PSA to the soil alone at the 6% to 8% by weight to the soil of soil were not significantly different (p < 0.05) compared with the lime stabilised soils.
The study concluded that periwinkle shell ash in the range 6 % to 8 % by weight of soil can be used as stabil.iser in improving the strength of clay subgrade soil for road construction.
Description
xix,180 pages
Keywords
Clay, Surbgrade Soil, Periwinkle Shell Ash, Road Construction, Ikorodu, Lagos State
Citation
Fajobi,B.O(2015).A study stabilisation of Clay subgrade soil using periwinkle shell ash