The Influence of Clay Soil Stabilization Using Nickel Slag on Unsoaked CBR Values

Abstract

The subgrade soil is the most critical layer in road pavement structures, serving as the foundation supporting traffic loads. The strength of this subgrade also influences the required thickness of the pavement layers. In many road construction projects, the subgrade soil often exhibits a California Bearing Ratio (CBR) of less than 5%, indicating low bearing capacity and high swelling potential, necessitating soil stabilization. Nickel slag, a by-product of ferronickel smelting, contains high levels of silicate and lime, making it a suitable additive for soil stabilization. This study investigates the effect of nickel slag on soil characteristics by utilizing four different variations of slag content: 0%, 15%, 30%, and 45%, based on the dry weight of the soil. The soil samples were cured for 0, 3, and 7 days and subjected to liquid limit, plastic limit, and unsoaked CBR testing. According to the Unified Soil Classification System (USCS), the soil was classified as organic clay with medium to high plasticity (OH). The test results revealed that the unsoaked CBR value of the untreated soil was 2.9%. Upon stabilization, the maximum unsoaked CBR value increased to 22.65% with the addition of 45% nickel slag. Furthermore, the soil's plasticity index decreased from 18.25% to 8.64%, significantly reducing the soil's shrinkage potential. Nickel slag has proven to be an effective additive for enhancing subgrade soil properties, improving its bearing capacity, and reducing plasticity, making it a viable option for road pavement stabilization.