Long-term photo oxidation aging investigation of temperature-regulating bitumen based on thermochromic principle

摘要

Bitumen modified by reversible thermochromic microcapsules (also called thermochromic bitumen (TB)) is a type of innovative and green paving material that can make the bitumen pavement work within a reasonable service temperature range and also efficiently mitigate the urban heat island effect. However, as organic materials, reversible thermochromic microcapsules are susceptible to ultraviolet (UV) radiation and gradually damaged when the TB serves in the field, which may result in compromise or even loss of temperature-regulating functionality shown by TB. Consequently, it is necessary to investigate the resistance of TB against long-term photo oxidation aging. The relationship between indoor accelerated UV aging simulation and outdoor solar radiation field aging was built by two-reaction kinetic aging model (TKAM). Then, pavement performance related rheological parameters obtained from dynamic shear rheometer (DSR) tests were utilized to characterize the property evolutions of TB during long-term UV radiation aging. Further, chemical components and structures analyses and micromorphology observation were conducted to ascertain the UV aging mechanism and durability of TB. The results indicate that the aging effect of 30-day indoor accelerated UV aging is almost equivalent to that of 50-month outdoor solar radiation aging. Unlike control sample, pavement performance related rheological parameters of TB are prone to keep stable since indoor accelerated UV aging 20th day. In addition, reversible thermochromic microcapsules can slow down oxidation of bitumen matrix due to their barriers to thermal and UV radiation and their release of methyl stearate during later stage of aging. The effectiveness of functionality for TB can be maintained during initial 15 days of indoor accelerated UV aging.