Laboratory simulation of the impact of solar radiation and moisture on long-term age conditioning of asphalt mixes

Abstract

Ageing is a renowned phenomenon for pavement engineers that can substantially affect the durability and long-term performance of flexible pavements. Several factors affect the mechanism of age-related changes, including asphalt cement’s chemical composition, mix properties, and environmental conditions. Most of the laboratory accelerated age hardening procedures are trying to simplify conditioning by considering heat as the main affecting factor and neglecting the others, such as humidity, precipitation, and solar radiation. This research aims to examine the validity of such an assumption and evaluate the effect of photo-oxidation, moisture and precipitation on the chemical and rheological properties of the asphalt cement and mix.In this research, a plant produced asphalt mix was selected and subjected to four different age conditioning procedures including Long-Term Oven Ageing procedure (AASHTO R30), Atlas® Whetherometer™, and using a bespoke chamber by applying dry and wet cycles of solar radiation and water conditioning. After running the Complex Modulus test on unconditioned and conditioned asphalt mix samples, asphalt cement was recovered and subjected to chemical and rheological analysis. The 2S2P1D model was employed to develop Complex Modulus and Phase Angle master curves. Results of this research showed that concerning chemical changes, extended heating at excessively high temperatures would result in different chemical products of oxidation as compared to solar radiation technique in terms of Carbonyl and Sulfoxide Indices. Moreover, it was observed that the extended heating procedure resulted in less stiffening at the low-temperature range in comparison with solar radiation. From the results of this research, it can also be concluded that water plays a vital role in the age conditioning procedure using solar radiation.