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

Master of Science (MS), Ohio University, 2022, Civil Engineering (Engineering and Technology)

As stated in the House Bill 62 Transportation Budget in Brief, roughly 5 billion dollars is spent yearly on road pavement construction in the state of Ohio, with a significant chunk for maintenance. Moreover, maintenance activities and their associated costs are increased in the colder regions of the US where damages and distress on roadways are associated to the Low Temperature Cracking (LTC) phenomena or at least in combination with other distress like rutting and fatigue cracking. Thermally induced internal cracking is a mechanism that occurs under low temperature conditions. Akentuna et al. (2017) postulated that the differential in Coefficient of Thermal Contraction (CTC) values in asphalt binder and aggregate gives rise to thermally induced internal cracking at low temperatures. Owing to its potential significance and effect on LTC modeling, this study investigated the thermally induced thermal cracking phenomena using the Indirect Tensile (IDT) test. The IDT test was selected since it is the test procedure used in fracture property investigation in the AASHTOWare Pavement Mechanistic Empirical (ME) Design program for low temperature cracking modeling. In addition, a study on the effect of loading rate and temperature on asphalt mixtures during the ITS test was also investigated. Although thermally induced internal cracking was observed by Li et al. (2007) using the acoustic emissions test and Behnia et al. (2014) using the Disc-shaped Compact Test (DCT), its quantified effect has not been studied. The results garnered from this study validated the occurrence of thermally induced internal cracking, evidenced by significant reduction in IDT peak strengths and energy at peak stress to averaged magnitudes of 4% and 12% respectively. The second objective of this study on varying loading rate and temperature during the IDT strength tests proved that the standard test loading rate of 12.5mm/min rate was too fast and not representative of f (open full item for complete abstract)

Committee: Issam Khoury Dr. (Advisor); Bhaven Naik Dr. (Committee Member); Benjamin Sperry Dr. (Committee Member); Eung Lee Dr. (Committee Member) Subjects: Civil Engineering

Master of Science, University of Toledo, 2018, Civil Engineering

Short, single-unit trucks with heavy, closely spaced axle-loads, referred to as Specialized Hauling Vehicles (SHVs), have lower load ratings than AASHTO legal loads. SHVs may cause forces by more than fifty percent in certain cases. These higher-force effects are for bridges with shorter spans, or elements with shorter load lengths, such as transverse floor beams. Per the FHWA, the Ohio Department of Transportation was required to incorporate SHVs in their load-rating basis and post bridges. This would require ODOT to load rate thousands of bridges. An initial comparison of moments produced by SHVs showed an increase of approximately twenty-five percent over the Ohio legal trucks. Therefore, ODOT divided its bridge inventory into three groups: • Group A - Ohio Legal Rating Factor ≥ 1.35 • Group B - 1.00 ≤ Ohio Legal Rating Factor ≤ 1.35 • Group C - Ohio Legal Rating Factor ≤ 1.00 ODOT hypothesized that Ohio bridges with their longest span less than 200 feet and rating factor (RF) ≥ 1.35 for Ohio legal loads will have a RF ≥ 1.0 under SHV loads. Thus, bridges with a rating factor greater than 1.35 would not require load rating for SHVs. If this hypothesis is correct, the number of bridges requiring load rating would be reduced by an order of magnitude. This hypothesis was tested through load rating of an existing 187 bridges and parametric studies. The author rated twenty-five slab, twelve PS I-beam, thirteen PS box, and twenty-eight steel bridges. A parametric model for single span bridges was developed by the author. To test the hypothesis in a broad way, results from all 187 bridges were analyzed in this thesis. Ratings for all the bridges satisfy the hypothesis. However, two out of thirty-three prestressed box beam bridges, and one out of thirty steel simple span bridges had a ratio of Ohio legal load RF to SHV RF greater than 1.35. This means that a similar bridge with an Ohio legal load RF equal to 1.35 would have had an SHV RF less than 1.00. The (open full item for complete abstract)

Committee: Douglas Nims (Committee Chair); Brian Randolph (Committee Member); Eddie Chou (Committee Member) Subjects: Civil Engineering