Microstructure of Warm Mix Asphalt Binder Exposed to UV Light and Heat
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Copyright 2016 by Mairepav8 2016 Organizers. This paper aims to evaluate the suitability of using warm mix asphalt (WMA) technology in countries with hot climates such as Qatar. For this purpose, an original and two WMA binders were investigated before and after aging. A new aging protocol that takes into account the combined effect of UV radiation, oxygen and typical summer day and night temperatures registered in Qatar is here proposed. The parameters were chosen in order to simulate the weather conditions in Qatar. The microstructure of the exposed binder surface was investigated with atomic force microscopy (AFM) and compared with the unaged surface. This evaluation is more accurate than previously used microstructural evaluations based on the observation of asphalt binder after Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV) aging. In the proposed method, the exposed surface is directly observed and any rearrangements of the binder components after aging (i.e. during heat treatment to obtain a smooth surface) is prevented. Profound changes in the microstructural features were observed due to aging. Each binder presented a different microstructure of the aged surface and the common feature among the different binders was the disappearance of the bee-like structures. Degradation of the binder surface was correlated with chemical reactions caused by UV radiation and oxygen. Moreover, the effect of a relatively high temperature during the aging process may have aggravated the damage, due to the synergic effect of many factors. This may be the reason of the short service life of pavements in Qatar.
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Proceedings of the Eighth International Conference on Maintenance and Rehabilitation of Pavements
