Abstract
The Hamburg wheel tracking test (HWTT) is widely used to evaluate the performance of asphalt mixtures. According to HWTT specifications, the stripping inflection point (SIP) and the rut depth at a certain number of load cycles are two common indicators for evaluating the moisture susceptibility and rutting resistance of asphalt mixtures, respectively. Although these indicators have been used extensively by several transportation institutions, the reliability and stability in evaluating asphalt mixture behaviors of these indicators have been questioned. To more effectively evaluate the performance of asphalt mixture in the HWTT, this study introduces a novel method of analysis for the HWTT and novel indicators of rutting resistance and moisture susceptibility. The proposed method and indicators were employed to analyze the HWTT results of 14 field core specimens, and the proposed indicators were compared with conventional HWTT indicators to assess their capability of distinction between asphalt mixtures with different performance behaviors in the HWTT. The results indicate that the conventional HWTT indicators cannot effectively evaluate the asphalt mixtures with different performance in the HWTT. By contrast, the proposed analytic method and indicators have significant advantages to effectively evaluate and distinguish the rutting resistance and moisture susceptibility of asphalt mixtures.
Highlights
The Hamburg wheel tracking test (HWTT) was developed by Esso A.G. in Hamburg, Germany [1].The test involves immersing an asphalt concrete specimen in a water bath at a specific temperature, generally 50 ◦ C, and using a steel wheel for repeated loading to determine the relationship between the load cycle and rut depth
The results revealed that the number of loading passes at failure, rut depth at 20,000 wheel passes, and stripping inflection point (SIP) are related to the nominal maximum aggregate size (NMAS) and that the creep slope is not significantly related to NMAS
The results show that M-1 before 13,000 load cycles had larger permanent strain, whereas the opposite trend was observed as load cycle increased
Summary
The test involves immersing an asphalt concrete specimen in a water bath at a specific temperature, generally 50 ◦ C, and using a steel wheel for repeated loading to determine the relationship between the load cycle and rut depth. Specimens used in the HWTT can be either a slab specimen or cylindrical specimen. Slab specimens are generally fabricated in a laboratory with a slab compactor, whereas cylindrical specimens can be prepared using a Superpave Gyratory Compactor (SGC) in the laboratory or obtained from cores onsite [2]. The HWTT has been widely used in laboratories to evaluate the rutting resistance and moisture susceptibility of asphalt mixture. Numerous studies have assessed the effectiveness of various wheel tracking tests in evaluating the rutting resistance and moisture susceptibility of asphalt mixture
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