Life-cycle assessment of using sulfur-extended asphalt (SEA) in pavements

With the excess of sulfur by-product in many oil and gas producing countries, engineers must find new markets that can successfully use this by-product. One application of using excess sulfur by-product has emerged in the use of sulfur as a partial substitute for bitumen in roadways. This sulfur-extend asphalt (SEA) can be used to replace 20-40% by mass of bitumen in dense-graded and warm-mix asphalt concrete mixtures, acting as an asphalt extender and mix stabilizer. The primary objective of this research is to evaluate the environmental impact of using SEA mixtures in pavements compared to that of other asphalt concrete mixes used in the Kingdom of Saudi Arabia (KSA). A comprehensive life-cycle assessment (LCA) was conducted in this study. The assessment considered the entire life-cycle of the pavement from production, use, maintenance and rehabilitation, end-of-life treatment, recycling, and final disposal (i.e., cradle to grave), using guidelines from the International Organization for Standardization (ISO 14040). The inventory databases and LCA framework developed were incorporated into a software developed as part of the study, sulfur extended asphalt life cycle tool (SEL²ECT 1.0). A series of case studies were investigated as a part of this study. Four different pavement designs and life-cycle scenarios were evaluated using SEL²ECT 1.0. The case studies showed that the use of SEA modified mixture can result in some reduction in environmental impacts over similar conventional mixture depending on the performance and future rehabilitations of pavement.