TEAGE: A new lab method to simulate field aging of asphalt pavements
2/1/2019
Asphalt pavements harden constantly beginning with their conception in pavement plants, through placement and compaction in the field, continuing until the end of service life.
A number of factors contribute to the hardening of asphalt concrete (AC) mixtures. As asphalt materials age, they become stiffer, more brittle, and over time, are more prone to cracking.
Asphalt pavement aging is primarily the result of oxidation. Oxidative aging accelerates at higher temperatures (thermal oxidation) and in the presence of ultraviolet radiation (photo-oxidation). Other factors affecting the oxidation rate include moisture exposure and ambient pressure. Thermal oxidation is the primary source of aging, and rapidly increases the stiffness and viscosity of asphalt binder during the production and laydown stages where temperatures are high and oxygen is plentiful. Then, aging slowly progresses over the service life of asphalt pavements due to the compounding effects of both thermal and photo-oxidation.
Asphalt binder is complex hydrocarbon with its chemical composition source-dependent. The variability in chemical makeup determines its reaction speed with oxygen—or its aging rate. The AC aging rate is impacted by the geographic location, temperature, and UV radiation.
To better understand the long-term behavior of asphalt pavement and to select proper materials to delay potential cracking, accelerated aging was simulated. Superpave™️ binder specifications, currently used in the US, involve short- and long-term aging methods. The long-term aging simulation is performed using the Pressure Aging Vessel method, which applies high temperature and pressure to accelerate pavement aging rate. This method is believed to simulate 7–10 years of field aging. However, the PAV method doesn’t consider UV-radiation and moisture effect.
To address the aforementioned shortcoming, a realistic and innovative aging equipment, Tecnico accelerated aging, was developed in collaboration with Lisbon University in Portugal (Ph.D. visiting scholar, João Crucho). TEAGE is capable of conditioning both binder and AC mixture samples with UV-rays, temperature, and moisture. Photo-oxidation in the chamber is applied using UV lamps to simulate solar radiation.