Doctor of Philosophy (PhD), Ohio University, 2022, Civil Engineering (Engineering and Technology)

The asphalt concrete (AC) base course contributes largely to the structural capacity of a layered asphalt pavement system. Due to its location in the cross-section, a failure of the AC base would require costly repairs. Therefore, it is important to use AC base courses that are durable. However, durability of AC bases courses seems often overlooked in flexible pavement research. This dissertation demonstrates the potential of a very practical approach to evaluate the durability of asphalt concrete base courses. Additionally, it presents the most reliable of the latest fracture parameters to be used for cracking characterization of AC base courses. Furthermore, provides an approach to evaluate the segregation potential of AC base courses. This dissertation addresses the lack of research on AC base course evaluation and provides the state agencies and construction companies with guidelines of more practical, inexpensive and time-efficient approaches to assess the design and quality of AC base mixtures. To achieve this, a four phases research was developed: 1) more than 50 projects, with different mixture composition and age range, were selected from all over the State of Ohio in order to collect pavement cores for laboratory testing; 2) an evaluation of the AC base mixtures fundamental material properties such as in-place density, moisture-induced damage and disintegration susceptibility (estimated from tensile strength ratio (TSR) and Cantabro mass loss (ML) test), and flexibility index (FI) and cracking resistance (obtained from Illinois semi-circular bending test, IL-SCB) was conducted; 3) a more time-efficient and sensitive procedure to characterize coarser AC base mixtures based on their cracking tolerance (estimating CTindex, using TSR data) was evaluated; 4) an approach to assess the segregation potential of AC base courses was explored. Cantabro mass loss was found to have potential as an approach to characterize the durability of AC base courses. Ne (open full item for complete abstract)

Committee: Shad Sargand (Advisor); Issam Khoury (Committee Member); Felipe Aros-Vera (Committee Member); Adam Fuller (Committee Member); Bhaven Naik (Committee Member) Subjects: Civil Engineering

Doctor of Philosophy, University of Akron, 2022, Civil Engineering

Over the last two decades transportation agencies are considering top-down cracking as one of the dominant forms of distress observed in pavements. There are different tests available to evaluate asphalt cracking resistance. The I-FIT and IDEAL-CT tests have received more attention in recent years because they require a relatively inexpensive testing device and the test can be conducted within a reasonably short period of time making these two tests easier to be implemented into mix design approval and quality control and quality assurance (QC/QA). The primary objective of this research study was to assist the Ohio Department of Transportation (ODOT) in identifying one of these two laboratory test that can be used to characterize the fracture behavior and cracking resistance of asphalt mixtures for potential incorporation into ODOT's mix design approval and quality control/quality assurance (QC/QA) process. In this study, a laboratory testing plan was developed and implemented that included performing both tests on a small number of asphalt mixtures for screening purposes and then choosing one of the two tests for full-scale evaluation using a larger number of asphalt mixtures that represented the majority of asphalt mixtures used by ODOT. The I-FIT and IDEAL-CT test results have a significant association, according to the screening evaluation. The results of the I-FIT and IDEAL-CT tests yielded a comparable ranking of asphalt mixes in terms of crack resistance, implying that one test may be used as a substitute for the other. Faster and easier sample preparation, applicability to asphalt mixtures containing larger aggregates, ability to achieve target air void level during compaction, availability of Excel spreadsheets to analyze test results, lower variation in test results, and familiarity of asphalt mix designers in Ohio with sample preparation and test procedure for contractors are some of the advantages that IDEAL-CT has over I-FIT. As a result, the IDEAL-CT (open full item for complete abstract)

Committee: Ala Abbas (Advisor); Ping Yi (Committee Member); Jun Ye (Committee Member); Yilmaz Sozer (Committee Member); Anil Patnaik (Committee Member) Subjects: Civil Engineering