DETERMINATION OF GEOTECHNICAL PROPERTIES OF PULVERISED BONE STABILISED LATERITIC SOIL

Abstract

Soils tend to shrink when they lose moisture, in particular lateritic soils are susceptible to shrinkage and often results in volumetric change. This is always the case in engineering structures (like embarkment dam) as a result of changing climatic conditions, simulated by cyclic wetting and drying in this study. Shrinkage can cause cracking of soils and result in significant deformation of engineering structures. Therefore, the objective of this study is to investigate possible improvement in the stability properties of lateritic soil by treatment with pulverized cow bone (PB). The effects of pulverized bone (PB) on the lateritic soil samples were evaluated by adding 4–16% pulverized bone (PB) with a constant increment of 4% to the lateritic soil. Prepared samples treated with and without pulverized bone (PB) were subjected to four dry-wet cycles. The drying of the samples occurred at 60℃ . Atterberg limit tests, unconfined compressive strength test and shear strength were carried out on the lateritic soil and lateritic- Pulverized bone (PB) mixtures and Chemical analyses of the lateritic soil and bone ash were conducted using X-rays Fluorescence Spectrometer test and Fourier Transform Infrared Spectrophotometer (FTIR). Results obtained showed that pulverized bone (PB) contained high proportion of Calcium oxide (CaO) and Silicon oxide (SiO). The lateritic soil had a liquid limit of 34.16%, a plastic limit of 64.26% and a plasticity index of 30.10%. The plasticity of the lateritic soil is high; hence the lateritic soil may be susceptible to cracking or shrinkage. The specific gravity of the lateritic soil was 2.48, while that of the pulverized bone (PB) was 2.25. The addition of pulverized bone (PB) to soil samples led to increase in soil shear strengths within the range of 44.13% to 63.61% over the strengths of the respective control tests. The values of the unconfined compressive strength increased from 88.26 –127.22 kN/𝑚2 with the addition of 0–8% Pulverized bone (PB), and there was a decline after 8% pulverized bone addition suggesting that optimum application to improve the stability after the application of cow bone is 8%. Similarly, optimum moisture content and maximum dry density occurred at 8% pulverized cow bone application to the lateritic soil. Therefore, the compaction and strength results did not suggest that pulverized bone can be added to the lateritic soil endlessly. The chemical reaction between silicon and calcium oxides, which were predominant in pulverized bone and lateritic soil respectively, may have implication for the engineering properties of the soil, due to their bonding attributes in the lateritic soil. Considering the cyclic wetting and drying effects on the soil samples, the samples showed a pronounced increase in the crack’s geometry and dimension after the first two cycles and tend to attain an equilibrium state after subsequent wetting- drying cycles. The soil treated with pulverized cow bone had a reduction in cracking depth and width as wetting and drying progresses. Also, a constant crack pattern was observed throughout the cyclic episode on the 8% treated sample. Therefore, emphasizing that the optimum application rate to reduce the crack in lateritic soil treated with cow bone is 8%. Results from this study has shown that pulverized cow bone have the potential to improve the geotechnical (strength) and physico-chemical properties of lateritic soils.