Mitigation of Greenhouse Gas Emissions by Fly Ash Stabilization and Sisal Fibre Reinforcement of Clay Subgrade for Road Construction

Abstract

Construction of bituminous pavements forms a major source of greenhouse gas emissions. In order to mitigate this effect, the research study proposes use of fly ash and sisal fibre in stabilization of clay soil for the pavement subgrade. The test specimens were impregnated with fly ash contents of 10%, 20%, 30% and 40% and fibre contents of 0.25% 0.50%, 0.75% and 1.0% of the dry soil mass and different geotechnical characteristics of the stabilized soils namely maximum dry density (MDD), optimum moisture content (OMC), California bearing ratio (CBR) and unconfined compressive strength (UCS) values were determined. Additionally, scanning electron microscopy tests were also carried out on the stabilized soil samples to know their surface morphology. Bituminous pavements sections with stabilized and non-stabilized subgrades were designed for 50 million standard axles traffic intensity in accordance with the standard codal provisions. The greenhouse gas emissions associated with construction of bituminous pavements were evaluated using standard inventories of carbon coefficients for road materials. The results indicated that key strength parameters of soil subgrade i.e. CBR and UCS were significantly enhanced with the use of fly ash and sisal fibre. The soil stabilization treatment significantly reduced the layer thickness eventually leading to reduction in the associated greenhouse gas emissions for the designed pavements. The results obtained are indicative of the potential utilization of fly ash and sisal fibre in building sustainable and durable bituminous pavements with reduced greenhouse gas emissions.