If you have any problems related to the accessibility of any content (or if you want to request that a specific publication be accessible), please contact us at firstname.lastname@example.org.
Comprehensive Evaluation of Asphalt Mixtures in Arid Climatic conditions
AdvisorHajj, Elie Y.
Civil and Environmental Engineering
AltmetricsView Usage Statistics
Raveling is the leading cause of poor performance in the asphalt-wearing course in Kuwait’s arid climatic conditions. The extreme conditions of Kuwait and poor asphalt mix design characteristics have further accelerated the raveling and deterioration of the in-service asphalt pavements. Combating this issue requires sophisticated asphalt mixture designing. Therefore, very recently, Kuwait has adopted the Qatari Superpave mix design procedure to improve the current condition of the asphalt pavement performance. In this study, a comprehensive evaluation of the existing Superpave mix design was undertaken, and the recommended modifications for the mix design were made to address raveling concerns in Kuwait.To carry out this study, local materials were collected from Kuwait, and their physical properties were evaluated to ensure their conformity with the latest specifications. After this, two mix designs, i.e., the traditional Marshall mix design practiced in Kuwait and the newly adopted Superpave mix design, were prepared as per the Qatari specifications. The performance of the finalized mix designs was evaluated through the indirect tensile strength ratio (TSR), Hamburg wheel-track test (HWTT), dynamic modulus (|E*| referred to as E*), cyclic fatigue (CF), and stress sweep rutting (SSR), at unconditioned (UC) and moisture-conditioned states at one freeze-thaw cycle (1-C) and three freeze-thaw cycles (3-C). The TSR, HWTT, and E* were performed for both the asphalt mix designs. However, the CF and SSR tests were only performed for the Superpave mix design based on the findings from TSR, HWTT and E* test at multiple freeze-thaw cycles and limitations in the material quantities. HWTT results showed that both asphalt mixtures (Marshall and Superpave) exhibited excellent resistance to moisture damage and rutting. TSR test results showed that the Marshall asphalt mixture had higher dry and wet indirect tensile strength (TS) than the Superpave asphalt mixture. However, the TSR values were higher for the Superpave asphalt mixture, indicating that the Marshall asphalt mixture was more susceptible to moisture damage. Similar observations were made for the E* test results, where the Marshall asphalt mixture showed higher stiffness initially than the Superpave asphalt mixture but lower moisture damage resistance than the Superpave asphalt mixture. Overall, HWT, TSR, and E* results showed that the newly adopted Superpave asphalt mixture was successful and proven to improve the moisture damage resistance of the mix compared to the Marshall asphalt mixture.To study the long-term resistance of the Superpave asphalt mixture to raveling, the CF and SSR results were used to assess the properties after multiple freeze-thaw cycles and to predict the asphalt pavement performance using mechanistic analysis. The CF and SSR results for the Superpave asphalt mixture showed that the mix after 3-C state accumulated more damage than the Superpave asphalt mixture at the UC state due to moisture intrusion. The fatigue index parameter (Sapp) showed that the allowable traffic level for Superpave asphalt mixture falls in the standard type category at both, UC and after 3-C state. However, in the rutting strain index (RSI), the Superpave asphalt mixture at the UC state was in the heavy traffic category type, whereas the mix went down to the standard category after 3-C state due to moisture damage. The mechanistic analysis showed that the current pavement structure in Kuwait is under-designed for all the traffic levels (3-30 MESALS). Further, the pavement sections in Kuwait failed in the fatigue cracking, indicating durability concerns throughout the pavement’s design life. Moisture intrusion in the asphalt mixture reduced the pavement’s fatigue and rutting life for all the traffic levels (3, 10, 30 MESALS), consistent with the results obtained from performance testing. Overall, the results showed that the recommended modifications to the current Kuwaiti mix design procedure successfully improved the rutting resistance of the asphalt mixture. However, cracking resistance still needs further improvement for the newly adopted Superpave asphalt mixture.