Abstract
Siluko borrow pit is one of the measure borrow pits in Benin that samples are taken from for road construction and other engineering work, but the borrow pit sample has low CBR which normally needs to be stabilized before using. This work studied the comparative analysis of lime and mechanical stabilization of Siluko borrow pit soil for earth road application and the X-ray fluorescence analysis, Fourier transform analysis and scanning electron micrograph analysis for lime stabilized borrow pit sample. X-ray fluorescence analysis was conducted on the lime stabilized soil to ascertain the presence of metals that may be responsible for the low CBR of the borrow pit. Fourier transform analysis was conducted in order to establish the effect of stabilization on weak soil, this was done by identifying the various functional groups represented by the different wavelength on the peaks of the Fourier transform analysis (FTIR) spectral. Scanning electron micrographs were taken in order to verify the presence of micro-pores in the structure of the weak soil compared to that of lateritic soil.
The borrow pit soil was stabilized with lime and quarry dust, lime was added in the sample from 2% to 12% at the interval of 2% and quarry dust was added from 5% to 35% at the interval of 5%. X-ray fluorescence analysis, Fourier transform analysis and scanning electron micrograph analysis for lime stabilized borrow soil were carried out at the percentages of lime at 0% (which served as the control), 6%, and 12% lime.
Based on the results of lime stabilization, it was observed that an increase in the level of lime stabilization resulted to an increase in the CBR from 14.45% at 0% lime to 30.88% at 12% addition of lime. From the foregoing, it is evident that the stabilized soil material falls in the A-2 soil, indicating good materials for sub-grade and sub-base materials for road construction. Also, the mechanical stabilization showed the variation in the CBR of the borrow pit soil occasioned by change in the amount of quarry dust added at 5% intervals is evident that the geotechnical properties of the soil material had improved very well with CBR increasing from 11.81% at 0% to 65.90% at 35%. X-ray fluorescence analysis showed the presence of heavy metals such as cobalt, iron, nickel, copper, arsenic and lead, which were possibly responsible for the weakness of the sample soil. This metal act as impurities and interferes with the behaviour and properties of the soil. With stabilization the concentration of such metals reduces with increase in the concentration of lime. Fourier transform analysis revealed that; alkyne group which was originally not present in lateritic soil and the weak soil was introduced when the soil was stabilized with lime. In addition, the (Al-O stretching) of aluminium which was absent in the weak soil was also introduced when 12% lime was added. It was observed in the scanning electron micrograph that the microstructural configuration of the weak soil tends towards crystallinity with increasing percentage of lime. It can be concluded therefore; that lime stabilization reduces the concentration of metals which act as impurities thereby improving the geotechnical properties of the soil. In addition, lime stabilization also enhances the concentration of vital elements such as calcium as observed.
