Disk-shaped Compact Tension Test for Asphalt Concrete Fracture

Abstract

ABSTRACT--A disk-shaped compact tension (DC(T)) test has been developed as a practical method for obtaining the fracture energy of asphalt concrete. The main purpose of the development of this specimen geometry is the ability to test cylindrical cores obtained from in-place asphalt concrete pavements or gyratory-compacted specimens fabricated during the mixture design process. A suitable specimen geometry was developed using the ASTM E399 standard for compact tension testing of metals as a starting point. After finalizing the specimen geometry, a typical asphalt concrete surface mixture was tested at various temperatures and loading rates to evaluate the proposed DC(T) configuration. The variability of the fracture energy obtained from the DC(T) geometry was found to be comparable with the variability associated with other fracture tests for asphalt concrete. The ability of the test to detect changes in the fracture energy with the various testing conditions (temperature and loading rate) was the benchmark for determining the potential of using the DC(T) geometry. The test has the capability to capture the transition of asphalt concrete from a brittle material at low temperatures to a more ductile material at higher temperatures. Because testing was conducted on ungrooved specimens, special care was taken to quantify deviations of the crack path frorn the pure mode I crack path. An analysis of variance of test data revealed that the prototype DC(T) can detect statistical differences Jn fracture energy resulting for tests conducted across a useful range of test temperatures and loading rates. This specific "analysis also indicated that fracture energy is not correlated to crack deviation angle. This paper also provides an overvwew of ongoing work integrating experimental results and observations with numerical analysis by means of a cohesive zone model tailored for asphalt concrete fracture behavior.

Rate- and Temperature-Dependent Fracture Characteristics of Asphaltic Paving Mixtures

“…Therefore, the magnitude of fracture energy at 0 C is greater than the fracture energy at À10 C over all the loading rates applied in this study. Regarding the trend of fracture energy to the loading rate, it decreases as the loading speed is faster, which agrees with observations in other studies [18,25]. At ambient temperatures (21 C and 30 C), the ratedependent fracture behavior is obvious, and the fracture energy increases as the loading rates become higher.…”

“…These are: (i) single-edge notched beam, SE(B), specimen [2,15,16]; (ii) disc-shaped compact tension, DC(T), specimen [17][18][19]; (iii) semi-circular bending, SCB, specimen [11,[20][21][22][23]; and (iv) double-edged notched tension, DENT, specimen [12]. Among the various options, SCB testing was selected in this study because it has several benefits compared to other fracture test methods.…”

“…Among the various options, SCB testing was selected in this study because it has several benefits compared to other fracture test methods. Even if it has some limitations [18], SCB testing is practically attractive in that it is very repeatable, simple to perform, and that multiple testing specimens can be easily prepared through a routine process of mixing and Superpave gyratory compacting of asphalt mixtures. Furthermore, the SCB geometry is even more attractive considering the fracture characteristics of field cores, which are usually circular.…”

“…There were several methods [10,18,[23][24][25] found in the open literature to calculate the fracture energy. Among them, this study attempted two approaches: one is based on the concept of the critical energy release rate and the other is by modeling the SCB fracture tests with cohesive-zone elements.…”

Influence Of The Gripping Fixture On The Modified Compact Tension Test Results: Evaluation Of The Experiments On Cylindrical Concrete Specimens

“…In the first case, the three point bending test (3PB) is applied to smaller beams either of dimensions 40 × 40 × 160 (120) mm 3 or 100 × 100 × 400 (300) mm 3 without reinforcement, see e.g. [2], [6] or [19]. In the second case the four point bend test (4PB) is applied mostly on larger reinforced concrete beams.…”