Abstract
To explore the significant factors related to the cracking resistance at low temperatures of asphalt mixture from mesoscopic perspective, asphalt fine aggregate matrix (FAM) was selected as the researched material because of its important role in mesoscopic structure of asphalt mixture. Bending Beam Rheometer (BBR) was utilized to investigate low-temperature properties of FAM. Due to the frequent occurrence of freeze-thaw action in seasonally frozen regions, this paper introduces a freeze-thaw cycle test. The structural characteristics of internal air voids in FAM and hot-mix asphalt (HMA) were analyzed using the industrial Computerized Tomography (CT). Results indicate that frost heaving damage of FAM-2.36 is more obvious than that of FAM-1.18, and the damage level increases as the bath temperature rises. After 32 freeze-thaw cycles, FAM-1.18 exhibits the rise of creep stiffness than original beams, and the hardening degree become serious with the decease of temperature. It could be concluded that the BBR has been proved to be an effective tool in evaluating the low-temperature properties of FAM. The expanding limit of small air voids and the hardening of binder in rich asphalt FAM contribute to completely different mechanisms of freezing-thawing damage within FAM. Therefore, asphalt content, fine aggregate passing rate and air voids size could be optimized through BBR test of FAM subjected to freeze-thaw cycle.
Highlights
Asphalt pavements are commonly used in highway pavement projects (Qian et al, 2021)
The maximum creep stiffness reduction rate for fine aggregate matrix (FAM)-1.18 occurs at −18°C, but for FAM-2.36 occurs at −6°C
The increase in water absorption rate indicates that the degree of freeze-thaw damage of FAM-1.18 did not increase significantly when compared to FAM-2.36, which can be
Summary
Asphalt pavements are commonly used in highway pavement projects (Qian et al, 2021). in seasonal freezing areas, freeze-thaw damage frequently occurs due to the large range of temperature changes between day and night, causing damage to the asphalt mixture such as loosening, falling particles, and potholes, reducing the overall strength and service life of the asphalt pavement (Wang et al, 2013; Shan et al, 2020; Li et al, 2021). FAM plays an important role in maintaining the performance of asphalt mixture especially for the low-temperature cracking (Dong et al, 2014), it is significant to conduct comprehensive testing on FAM and consider the influence of freeze-thaw cycle. FAM is well known as a complex multi-scale, multi-layer, and multi-component material (Underwood and Kim, 2013), fine aggregate size, asphalt content, and air voids are typical factors to be directly related to the low-temperature performance of FAM in extremely cold regions. This paper applies BBR to evaluating the low-temperature performance of FAM subjected to different freeze-thaw cycles, and explores the main factors leading to low-temperature shrinkage cracking in asphalt pavements at mesoscale.
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