Carbon footprint assessment of steel slag asphalt pavement in Singapore

Abstract

Electric Arc Furnace (EAF) Steel Slag is a by-product generated from the steel-making process which is being used as aggregates for the road construction wearing course.Replacement of naturally occurring aggregates with locally available EAF steel slag as a road construction material would promote sustainability of road construction, reduce carbon footprint and minimise the environmental impact of the steel making industry. Since 1994, 100% of steel slag generated in Singapore has been fully recycled into aggregates and used in the asphalt wearing course on roads by LTA and PUB and within the ports by PSA. Climate change is one of the greatest challenges of our time and a major threat to the livelihoods of living creatures on earth. Greenhouse gasses generated from human activities is no doubt the biggest contributor of climate change observed since the mid-twentieth century. Carbon footprint is one of the most widely used tools to quantify greenhouse gases for assessing the environmental impacts of a production activity. The amount of carbon dioxide and other greenhouse gases associated with a given product can be calculated and expressed asCO2 equivalent. This paper briefs the applications of steel slag aggregate for asphalt pavement in Singapore and compares the carbon footprint of locally produced steel slag aggregates with imported granite aggregates. The environmental benefits of using steel slag have been assessed through the comparison of embodiedCO2 emission values for steel slag aggregate and granite aggregate. Data used in the calculations include electricity usage, diesel consumption, transportation and use of explosives. The analysis reveals that carbon dioxide equivalent emissions decreases as the use of EAF steel slag aggregates increases. The transportation of granite aggregates into Singapore represents a significant contribution to its overall carbon footprint. Thus, using steel slag aggregates generated locally in Singapore would contribute a smaller carbon footprint to the asphalt wearing course making process and reduces the disposal of non-incinerable waste to the landfill site.