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Low temperature cracking is a very serious distress for asphalt pavements built in Northern U.S. and Canada. As temperature rapidly decreases, thermal stresses develop in the restrained asphalt surface layer and, when the temperature reaches a critical value, cracking occurs. A 'simple' solution to overcome this problem is to use a very soft asphalt binder with high relaxation properties, which limits the accumulation of high stress and the formation of cracks. However, these types of binder may lead to significant permanent deformation at high temperature (e.g., rutting) and, therefore, cannot be used for real pavement constructions. In this research, the possibility of obtaining stiffer asphalt binders by adding fine taconite filler available in Minnesota was investigated. Two different types of asphalt binders were selected and from each binder, three different types of asphalt mastics were prepared based on the amount (i.e., level) of taconite particles used as filler: 5%, 10% and 25%. Bending Beam Rheometer (BBR) and Dynamic Shear Rheometer (DSR) tests were performed to evaluate the low and high temperature properties of asphalt binder and corresponding mastics. From these experimental works, creep stiffness, m-value, thermal stress and shear complex modulus were calculated and then graphically and statistically compared. It was observed that asphalt mastic containing 5% taconite filler presents similar properties at low temperature and better performances at high temperature compared to the corresponding asphalt binder. On the other hand, asphalt mastics containing higher amount of taconite fines (10% and 25%) are much more brittle compared to the original binder at low temperature, even though higher rutting resistance was observed at high temperature. [ABSTRACT FROM AUTHOR]

This paper investigates the possibility of developing low temperature limit criteria for asphalt mixtures, similarly to what is currently available in the standard specification for asphalt binder. The investigation is based on extensive experimental work that includes Bending Beam Rheometer (BBR) creep tests on asphalt binders and asphalt mixtures at low temperature and on semi-empirical Hirsch model, and on the rheological model proposed by Christensen, Anderson and Marasteanu (CAM). Limiting asphalt mixture creep stiffness values are predicted from Pressure Aging Vessel (PAV; Long term aging) binder creep stiffness data and are next compared with results available in literature. Then, BBR creep data for Rolling Thin-Film Oven Test (RTFOT; Short term aging) asphalt binder are used to predict creep stiffness of the corresponding short term aged asphalt mixtures. Based on these results, a range of limiting stiffness values is obtained. Due to large variations in the calculated slopes of the mixture creep stiffness curves, a limiting value for the relaxation parameter m-value could not be recommended. [ABSTRACT FROM AUTHOR]

Using recycled materials in pavement applications is a viable option to reduce costs and limit the environmental impact of road construction. During the past decades, many agencies in the U.S. have investigated the effect on pavement performance of adding Reclaimed Asphalt Pavement (RAP), and, more recently, Recycled Asphalt Shingles (RAS) to asphalt mixtures, and limits were proposed on the amount of recycled materials which can be used. This paper investigates the effect of adding both RAP and RAS to virgin asphalt mixtures by means of a simple low temperature creep test performed on asphalt mixture beams. From the experimental work, creep stiffness, m-value, thermal stress and critical cracking temperature are calculated and compared statistically and graphically. Based on the results, it is concluded that most of the mixtures prepared with combinations of RAP and RAS perform similarly to standard mixtures at low temperature. For a limited number of mixtures, a negative effect is observed. [ABSTRACT FROM AUTHOR]