A Study on Radiation Cooling Effect on Asphalt Concrete Pavement Using Basic Oxygen Furnace Slag to Replace Partial Aggregates

In this study, aggregates in asphalt concrete were partially replaced by basic oxygen furnace slag (BOFS) in proportions of 45 wt.%, 55 wt.%, and 75 wt.%. The thermal performances of the specimens are discussed based on the thermal conductivity, emissivity, and the indoor and outdoor temperature measurements. Consequently, 75 wt.% of the specimen's aggregates were replaced by BOFS, which had a high emissivity of 0.86 across the sky window. In the indoor and outdoor tests, the temperature change was recorded to estimate the thermal performance of specimens. According to the quantitative calculation, when the substitution of BOFS was higher than 55 wt.%, the specimens had a better radiation cooling ability. Among these specimens, the specimen with the BOFS substitution of 75 wt.% absorbed the most heat inside the body, contributing to less heat remaining in the environment. Furthermore, because Newton's cooling energy accounted for about 90% of the stored energy within 7 h, the heat dissipation after the seventh hour was primarily radiation cooling, corresponding to the emission across the urban boundary layer. As for the mechanical properties, the stability value, indirect tensile strength, and British pendulum number (BPN) were in line with the specifications under the proper BOFS substitution. In conclusion, BOFS has great applicability in pavements due to its thermal performance and mechanical properties. It not only achieves the goal of urban heat island mitigation by radiation cooling, but also reflects the concept of resource sustainability.

Automated summary

The study found that partial replacement of aggregates in asphalt concrete with Basic Oxygen Furnace Slag (BOFS) improved the thermal and mechanical properties of the specimens, with 75 wt.% substitution showing high emissivity and heat radiation cooling ability. Furthermore, BOFS demonstrated good thermal radiation cooling effects and the concept of sustainable resource utilization.