Road Subgrade Stabilization Using Ground Granulated Blast Furnace Slag: Pavement Design, Cost Optimization, and CO2 Emission Reduction

This study examines the effects of using GGBFS in road subgrade stabilization on pavement structure and sustainability. Samples were prepared by adding GGBFS at ratios of 5%, 10%, 15%, and 20% to BT (Bentonite) soil samples evaluated as road subgrade. As a result of the laboratory experiments, the optimum GGBFS ratio was determined as 15%; this ratio provided increases of 109%, 185%, and 234% in California Bearing Ratio (CBR) values at 5.0 mm penetration depth (adopted as the primary structural design benchmark) at the end of 3, 7, and 28 days of curing, respectively, while Unconfined Compressive Strength (UCS) values increased by 124%, 166%, and 208%. Pavement thickness and cost designs carried out according to the AASHTO 1993 method revealed a reduction of up to 29.41% in flexible pavement thickness and up to 14.20% in unit area cost. For rigid (concrete) pavement, a reduction of up to 6.06% in thickness and 6.77% in unit area cost was identified. For a road with dimensions of 1000 m × 20 m, cost savings of up to 107,800 USD for flexible pavement and 70,792 USD for rigid pavement were calculated. The sustainability analysis based on CO2 emissions during initial construction demonstrated that the use of GGBFS reduced CO2 emissions by 11.95% in flexible pavements and 7.50% in rigid pavements. It was evaluated that the largest source of these emissions is the material production process, which accounts for approximately 57% of total emissions in flexible structures and approximately 95% in rigid structures.