Abstract
Asphalt concrete exhibit significant changes in its physical properties owing to the loss of volatile components and oxidation through the short-time aging of the binder that results from exposure to high temperatures during production in mixing plants. Because the moisture susceptibility of asphalt concrete mixes is highly dependent on binder chemistry and its physical property, consequently, the aging affects the moisture resistance of asphalt concrete pavements. However, the degree of this effect varies according to the morphology of the asphalt concrete mixture in addition to the mixture production temperature.
The objective of the current AASHTO R30 guidelines for the short-term aging of asphalt concrete is to mimic the oxidation and asphalt absorption into the aggregates that would occur for a typical dense hot-mix asphalt mixture. Within these guidelines, two variables are addressed, namely temperature and time. It is well documented in the literature that the production of asphalt mixtures with different aggregate gradation types as well as temperatures as in the case of warm mix asphalt affects the short-term aging conditions. Based on the aforementioned preface, research on this topic has become necessary.
To this end, job mix formulas were prepared in the laboratory for four types of wearing course mixes: densegraded hot-mix asphalt, open-graded friction course hot-mix asphalt, gap-graded hot-mix asphalt (stone matrix asphalt) and dense-graded warm-mix asphalt. The prepared job mix formulas were forwarded to a mixing plant, and four tons of asphalt concrete mixtures were produced (1 ton each) across four different batches. Samples were taken to the laboratory, and specimens were prepared and tested to determine their moisture susceptibility based on an indirect tensile strength ratio procedure. I contrast, laboratory-produced mixes with the same mix gradations as those of the plant-produced mixes were prepared and subjected to different aging conditions (temperature and time). Their moisture resistance was then evaluated. Finally, short-term aging conditions that accurately simulate the aging process at the mixing plant were determined.