Long-term releasing and migration characteristics of chloride ions in chloride-based asphalt mixtures

Abstract

Chloride-based pavement lowers freezing point of pavement surface and delays ice formation by releasing chloride ions. However, the long-term effectiveness of chloride filler has not been well-understood. This study combined the experimental and simulation methods to investigate the long-term releasing characteristics of chloride ions inside chloride-based mixtures. In this study, two types of chloride-based asphalt mixtures (AC-13 and OGFC-13) were prepared with Mafilon (MFL) and immersed in deionized water. The electrical conductivity tests were conducted on leaching water to evaluate the long-term releasing characteristic of chloride ions. The migration simulation was carried out on MFL AC-13 subjected to wet-dry cycles to explore the migration characteristics of chloride ions inside MFL AC-13 mixture. Results show that chloride ions experiences a rapid release within 30d in water, followed by a gradual and sustained release. Half of the chloride ions in mixture containing 70 % MFL will released into water after immersion for 278d at 20°C or 74d at 60°C, respectively. The long-term release of chloride ions can be significantly improved by increasing the MFL dosage in asphalt mixtures. Chloride ions in mixture surface preferentially released into leaching water, resulting in a higher concentration of residual chloride in core of the mixture. During the drying phase, the chloride ions concentration throughout the asphalt mixture tends to become uniform as drying time increases. The findings achieved in this study would benefit and promote the better use of MFL in anti-icing pavement.