United States Department of Transportation
i
Impact of Truck Loading on Design and Analysis of Asphaltic Pavement Structures-Phase IV: Mixed-Mode Fracture Characterization
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2014-12-01
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[PDF-7.16 MB]
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Edition:Final Report
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Abstract:Cracking in asphalt concrete pavements causes primary failure in the pavement structure. It is considered one of the key issues to be addressed when selecting paving materials and designing sustainable pavement structures. Due to the diverse nature of truck loads and pavement geometry, the asphalt mixture in the pavement is subjected to complex cracking behavior, such as mixed-mode fracture, which is a combination of opening mode and shearing mode of fracture. For a better understanding of asphalt fracture and a more accurate design of pavement structure, mode-dependent fracture behavior needs to be characterized. This study presents integrated experimental-numerical efforts to characterize the mixed-mode fracture of a fine aggregate matrix (FAM) which is the primary phase of cracks around stiffer coarse aggregates when typical asphalt concrete mixtures are subjected to heavy truck loads at intermediate service temperatures. Experimentally, semicircular bend (SCB) fracture tests were conducted by varying the geometric-loading configurations with different initial notch inclination angles and supporting spans to achieve different fracture modes (opening, shearing, and mixed). The SCB fracture test results were then integrated with the extended finite element modeling which is also incorporated with mode-dependent cohesive zone fracture to properly identify the mode-dependent fracture properties. The test and model simulation results indicated that the cohesive zone fracture toughness of mode-II (shearing) is quite different from mode-I (opening) fracture toughness. The critical fracture energy was related to the mixed-mode ratio, which presented a power relationship between the total fracture toughness and involvement of mode-II fracture in the total. Findings and observations from this study, although they are limited at this stage, imply that the mixed-mode fracture characteristics are significant and need to be considered in the structural design of asphalt pavements with which multiaxial cracking is usually associated.
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Content Notes:Sponsoring Agency Code: MATC TRB RiP No.34756
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