Abstract
As an inherent characteristic of materials, the fracture toughness is an important parameter to study the cracking behavior of asphalt concrete mixtures. Although material compositions and environmental conditions have a significant effect on the fracture toughness, for a certain material and testing environment, the test condition including the specimen configuration and loading type may also affect the obtained fracture toughness. In this paper, the effect of specimen configuration and applied loading type on the measured pure mode-I fracture toughness (KIc) is investigated. In order to achieve this purpose, using a typical asphalt mixture, four different test specimens including Semi-Circular Bend (SCB), Edge Notch Disc Bend (ENDB), Single Edge Notch Beam (SENB) and Edge Notch Diametral Compression (ENDC) disc are tested under pure mode I. The mentioned specimens have different shapes (i.e., full disc, semi-disc and rectangular beam) and are loaded either with symmetric three-point bending or diametral compressive force. The tests were performed at two low temperatures (−5 °C and −25 °C) and it was observed that the critical mode-I fracture toughness (KIc) was changed slightly (up to 10%) by changing the shape of the test specimen (i.e., disc and beam). This reveals that the fracture toughness is not significantly dependent on the shape of the test specimen. However, the type of applied loading has a significant influence on the determined mode I fracture toughness such that the fracture toughness determined by the disc shape specimen loaded by diametral compression (i.e., ENDC) is about 25% less than the KIc value with the same geometry but loaded with the three-point bending (i.e., ENDB) specimen. In addition, the fracture toughness values of all tested samples were increased linearly by decreasing the test temperature such that the fracture toughness ratio (KIc (@−25 °C)/KIc (@−5 °C)) was nearly constant for the ENDB, ENDC, SCB and SENB samples.
Highlights
As a composite material, asphalt is the most used material for paving the roads.The main components of asphalt are bitumen and aggregates and due to the brittleness of mastic and fine aggregate matrix and binder at low temperatures, the behavior of this material is mainly brittle or quasi-brittle especially at low-temperature conditions [1,2,3,4,5].Brittle fracture phenomenon resulting from cracking is one of the major degradation mechanisms of asphalt pavements, especially in cold regions or during the winter season.the design and manufacturing of asphalt mixture with high resistance against cracking is an achievement for the pavement engineers
The design and manufacturing of asphalt mixture with high resistance against cracking is an achievement for the pavement engineers
Fracture toughness is an important parameter in the framework of fracture mechanics that describes the resistance of material against crack propagation [6,7,8]
Summary
Asphalt is the most used material for paving the roads.The main components of asphalt are bitumen and aggregates and due to the brittleness of mastic and fine aggregate matrix and binder at low temperatures, the behavior of this material is mainly brittle or quasi-brittle especially at low-temperature conditions [1,2,3,4,5].Brittle fracture phenomenon resulting from cracking is one of the major degradation mechanisms of asphalt pavements, especially in cold regions or during the winter season.the design and manufacturing of asphalt mixture with high resistance against cracking is an achievement for the pavement engineers. The main components of asphalt are bitumen and aggregates and due to the brittleness of mastic and fine aggregate matrix and binder at low temperatures, the behavior of this material is mainly brittle or quasi-brittle especially at low-temperature conditions [1,2,3,4,5]. Brittle fracture phenomenon resulting from cracking is one of the major degradation mechanisms of asphalt pavements, especially in cold regions or during the winter season. The design and manufacturing of asphalt mixture with high resistance against cracking is an achievement for the pavement engineers. Fracture toughness is an important parameter in the framework of fracture mechanics that describes the resistance of material against crack propagation [6,7,8].
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