The experimental assessment of cracking distresses in asphalt concrete pavements is crucial to the longevity of pavements. As such, fracture parameters obtained from experiments play a key role in facilitating the use of fracture mechanics theories and prediction of cracking distresses in asphalt concrete (AC) pavements. The stress intensity factor (SIF) is among the fracture parameters derived from fracture mechanics theory. Many fracture mechanics based laboratory tests have been developed with the goal of calculating such key fracture parameters. The C* Fracture test is unique among them because it incorporates rate dependent loading into the calculation of fracture parameters via the theory of the C* Line integral. However, unlike other laboratory fracture tests, the C* Fracture test does not have any analytical solution or previous sources from literature which describe geometric shape factors used in the calculation of SIFs. Numerical modeling of the C* Fracture test specimen is also limited in literature. Therefore, there is a need for a high-fidelity numerical model of this fracture test in order to develop SIF functions. In this thesis, the numerical models of the C* Fracture test were developed using the Generalized Finite Element Method (GFEM). GFEM is particularly effective at modeling problems with discontinuities in complex 3-D structures. The use of the GFEM to solve this problem allows a high-fidelity numerical model to be created without a large computational cost and labor intensive mesh crafting. After verifying the model accuracy using convergence analysis, the specimen geometry was modeled by changing the crack size. A SIF function was developed that includes a specific geometry dependent shape factor for the C* Fracture test based on Linear Elastic Fracture Mechanics (LEFM).
United States Air Force airfield PAVER pavement management system enterprise data was reviewed for 67 networks. The distress survey extents and severity fields were joined with treatment costs estimated using RSMeans to determine the costliest distress. In asphalt surfaced pavements Longitudinal/transverse cracking, weathering, and block cracking resulted in the most pavement condition index (PCI) deducts while the costliest distresses are weathering, block cracking and longitudinal cracking. In portland cement concrete surfaced pavements linear cracking, joint seal damage, and joint spalling resulted in the most PCI deducts while the costliest distresses are joint seal damage, linear cracking, and corner spalling. The results of this data were then compared to airfield attributes: Pavement Temperature Group, Dominant American Association of State Highway and Transportation Officials (AASHTO) Soil Classification, Pavement- Transportation Computer Assisted Structural Engineering (PCASE) Climate Zone, and years since last maintenance. Maps showing the Pavement Temperature Group, Dominant AASHTO Soil Classification, and PCASE Climate Zone are included in Appendix A. Alligator cracking is most prevalent at the airfields with PTG 64-34 (Ellsworth, Fairchild, Hill, and Offutt) and 58-22 (Niagara and Vandenberg). Rutting is most prevalent at PTG 64-34 (Ellsworth, Fairchild, Hill, and Offutt). An increasing trend of joint spalling, corner spalling, and corner break with decreasing soil quality (AASHOTO A-1 to A-8 soils). The PCASE Climate Zone Cost Indices the cost index for weathering is approximately double in the moist region over the dry region. The cost index for block cracking is approximately double in the cold region over the hot region. It is recommended that the agency review its pavement performance modeling in the pavement management system to increase the recommendation of pavement preservation treatments and review the use of higher quality materials for pavement maintenance treatments.
In this research, an effort was undertaken to gather and collect most recent asphalt mixtures’ design data and compare it to historical data such as those available in the Long-Term Pavement Performance (LTPP), maintained by the Federal Highway Administration (FHWA). The new asphalt mixture design data was collected from 25 states within the United States and separated according to the four suggested climatic regions. The previously designed asphalt mixture designs in the 1960’s present in the LTPP Database implemented for the test sections were compared with the recently designed pavement mixtures gathered, and pavement performance was assessed using predictive models.
Three predictive models were studied in this research. The models were related to three major asphalt pavement distresses: Rutting, Fatigue Cracking and Thermal Cracking. Once the performance of the asphalt mixtures was assessed, four ranking criteria were developed to support the assessment of the mix designs quality at hand; namely, Low, Satisfactory, Good or Excellent. The evaluation results were reasonable and deemed acceptable. Out of the 48 asphalt mixtures design evaluated, the majority were between Satisfactory and Good.
The evaluation methodology and criteria developed are helpful tools in determining the quality of asphalt mixtures produced by the different agencies. They provide a quick insight on the needed improvement/modification against the potential development of distress during the lifespan of the pavement structure.