Effects of Gliricidia sepium ash for stabilization of abattoir polluted soils

Abstract

Abattoir effluents, improperly disposed of, can contaminate and cause adverse effects on nearby soils thereby altering their physical and engineering properties. This necessitates the stabilization of these soils. This study aims to determine the effect of Gliricidia sepium ash (GSA) on contaminated lateritic soils as a stabilization agent. The GSA was mixed with the soil specimen in different ratios (0%, 2.5%, 5%, 7.5%, and 10%), by the dry weight of the soil sample. Characterization tests were also carried out on the GSA while the test specimens were subjected to various laboratory analyses including particle size distribution, compaction characteristics, California bearing ratio (CBR), unconfined compressive strength (UCS), direct shear and permeability test to determine the soil response to the addition of GSA. The results show there was an overall improvement in the strength properties of the soil specimen. This was achieved at 10% GSA addition, there was also an increase in UCS and CBR by 61.5% and 19.7% respectively. In contrast, the permeability showed a steady decrease with a simultaneous increase in GSA content. This property response to GSA could be attributed to the void filling action of the ash, hydration/cation exchange reaction, and micro-fabric changes. Findings reveal that the strength properties of the GSA-soil mixture (CBR-33%; UCS-837.7KNm2 @ GSA-10%) make it suitable as a sub-base material for lightly trafficked rural roads having met requirements given by the Federal Ministry of Works. X-ray Fluorescence Spectroscopy test carried out shows GSA as pozzolanic material containing proportions of SiO2, Fe2O3, and Al2O3 (>70.0 mg/cm2) which governs its cementitious behavior. A 10% by soil weight of Gliricidia sepium ash in ratio 1:1 stabilized lateritic soil could be used as a potential subbase material for highway construction.