Geochemical and Microstructural Characteristics of Lateritic Soil Treated with Steel Slag for Road Foundation Applications

Abstract

Reusing industrial waste is a sustainable and eco-friendly way of minimizing environmental pollution in society. In addition, the stabilization of soils with non-conventional stabilizers has been shown to ameliorate engineering features of soils and reduce the cost of construction of road works. This study investigated the impacts of steel slag (SS) on the properties of poor lateritic soil (LS) for road pavement applications. Varying percentages of steel slag from 0-30% of soil dry weight in 5% intervals were employed to stabilize the soil. Plasticity index (PI), Maximum dry density (MDD), Optimum moisture content (OMC), California Bearing Ratio (CBR), Uniaxial Compressive strength (UCS), and chemical composition including the microstructural analysis of the untreated and treated soil were evaluated. With increasing slag content, the PI value decreased significantly from 22.47% to 9.20% indicating a nearly 60% reduction in PI at 20% SS treatment. The soil density became higher with a corresponding decrease in OMC as the SS content increased. The MDD increased from 1.56 g/cm 3 for natural soil to 2.10 g/ cm 3 at 25% SS content, and further addition of the material reduced the soil density. The CBR and UCS results show a general increase in values with higher SS content. The soaked CBR increased from 11.55 – 22.32% as SS content increased from 0-30%. The 28th day UCS reached the optimum value of nearly 380 kN/m 2 at 25% SS compared to 93.57 kN/m 2 of the natural soil. The iron oxide, which is a cementing agent, increased as the content of SS became higher in the soil. The microstructural analysis using scanning electron microscopic (SEM) results showed the formation of larger particles and a reduction in pore spaces as the SS content increased. The 25% SS treated soil satisfies the required 12% PI and minimum soaked CBR of 20% for foundation application as a subbase material in light traffic roads. These results suggest that adding 25% steel slag makes the lateritic soil a suitable material for both subgrade and sub-base pavement layers.