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The purpose of this study is to examine potential relationships between fatigue and fracture parameters obtained from standardized laboratory tests. A flexural bending beam test was used to obtain two fatigue parameters, which include a traditional fatigue criterion based on stress or strain to find number of cycles to failure and a new fatigue criterion based on an energy approach known as the plateau value (PV). Similarly, a disk-shaped compact tension DC(T) fracture test was used to obtain fracture energy parameters, including: fracture strength, pre-peak fracture energy, post-peak fracture energy, and total fracture energy. A factorial of the eight possible correlations was computed to determine the strongest association between the fatigue and fracture parameters for the asphalt mixtures investigated. The study was motivated by the desire to investigate the feasibility of predicting time-consuming fatigue test results with fracture test results, which can be obtained much more rapidly. Based on the results obtained in this study, it was shown that a potentially strong correlation exists between fatigue and fracture mechanisms in asphalt concrete, as characterized by parameters associated with dissipated or consumed energy. As presented through the statistical analysis, the plateau value (PV) and the pre-peak fracture energy (Gf-pre) are the most highly correlated parameters from the fatigue and fracture tests, respectively. This study is based upon limited experimental data and is explored an initial starting point to find relationships between fatigue and fracture mechanisms. Much more experimented and analytical work will be needed to fully understand these relationships and to develop a standardized interconversion scheme.
Abstract: Fatigue cracking is a primary distress in asphalt due to repetitive stresses and strains caused by traffic. The main objective of this study is to investigate the use of the semi-circular bend (SCB) test as a quality assurance/quality control (QA/QC) measure for field construction. The SCB test parameters were determined using two methods, the first of which was cross-head movement (CHM), and the second was non-contact camera. In SCB CHM method the specimens were loaded monotonically until fracture under a constant cross-head deformation, while in none-contact camera method a camera was fixed in front of the SCB specimen to measure the crack length. In addition beam-fatigue test (BFT) was conducted according to AASHTO T-321 on the same mixtures. A comprehensive comparison between the test results is performed. The results of this study indicate that the SCB test has a great potential as a QA/QC test of fracture properties of asphalt mixtures.
This book discusses the applications of fracture mechanics in the design and maintenance of asphalt concrete overlays. It provides useful information to help readers understand the effects of different material and loading type parameters on the fracture properties of asphalt concretes. It also reviews relevant numerical and experimental studies, and describes in detail design parameters such as aggregate type, air void, loading mode, and additives, based on the authors experience and that of other researchers.
Fatigue failure can be attributed to cyclic (dynamic) loading energy which induces stresses and/or strains below the allowable strength and/or fracture strain level of a material. Since fatigue failures evolve over time, damage theories have been postulated to describe the mechanism by which this failure occurs. When a crack exists or forms early in the life of a pavement, fracture mechanics becomes the most relevant theory to explain the damage process. If conditions prevail to promote brittle fracture, the stress intensity factor and its critical value, Kc (or Gc) , becomes the most relevant parameter controlling the cracking and fatigue damage process. If conditions prevail to promote ductile fracture, the ductile fracture parameter, Jc, becomes the parameter for consideration. If conditions prevail to promote creep fracture, the C* - Line Integral offers the most relevant fracture criteria. Since the definition of Jc or C* in fracture mechanics imposes the condition that either parameter will degenerate into Kc (or Gc) when brittle fracture conditions, prevail, the utilization of Jc or C* provides the user with a powerful tool to characterize the fatigue/fracture process in a more general form. Since asphaltic mixtures can exhibit brittle and/or creep fracture, it is apparent that the C* - Line Integral can more closely capture the fatigue/fracture damage process than Kc or Jc. In this paper, a simple laboratory procedure to determine the C* - Integral, which is interpreted as the energy release rate, is presented. In addition, a mixture efficiency factor (`?*) is introduced. The mixture efficiency factor is used to examine and compare the efficiency of asphaltic concrete mixture in resisting fracture cracking using different aggregates and asphalt cement binders.
Thirteen papers presented at the conference on [title], held in Phoenix, Arizona, December, 1994, discuss the products of the strategic highway research program, the Superpave method of mix design, and test methods for fatigue cracking and permanent deformation. Lacks an index. Annotation c. by Book
A substantial amount of experimental data is presented to verify a theoretical solution for predicting the fatigue life of asphalt concrete beams from fracture tests. The theory utilizes the principles of fracture mechanics and covers the full range of loading from low to high. The raw test data extracted from a report by Majidzadeh et al. [1] include dynamic modulus, ultimate tensile strength, critical stress-intensity factor, and fatigue life of asphalt concrete beams fabricated from over 46 different mixtures, consisting of three types of asphalts, five asphalt contents, three filler asphalt ratios, and several gradations. The fracture and fatigue tests were also conducted on one asphalt concrete mix at temperatures ranging from 16 to 35°C (35 to 95°F). The agreement between theory and experiment is excellent.