Comparison of Testing Method Effects on Cracking Resistance of Asphalt Concrete Mixtures

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.

A Comparative Study to Evaluate the Essential Work of Fracture to Measure the Fracture Toughness of Quasi-Brittle Material

“…The crack was created and inserted in the central zone A as a straight, plane strand of 15 mm length with the same specimen thickness. The initial geometry of the specimens and the initial shape of the precrack or crack length had no effect on the fracture toughness for stationary cracks as reported in [11,64,65], which reduces the number of specimens needed (only one crack length of the specimen is used). This form is preferable in FEM as the strain field around the crack tip becomes singular and the singularity improves the accuracy of the analyses.…”

Influence of testing method on mode II fracture toughness (KIIc) of hot mix asphalt mixtures

“…Most of the available test specimens have either cylindrical or rectangular beam shapes. [8][9][10][11][12][13][14][15] This is because making laboratory test sample in the mentioned geometries is easier than other geometries and shapes for asphalt mixtures. Center cracked circular disc (CCCD) specimen subjected to compression diametral force (often known as Brazilian disc), 16,17 semi-circular bend (SCB) specimen containing either vertical or inclined edge crack, [18][19][20][21][22][23][24][25][26][27] edge notch disc bend (ENDB) specimen, [28][29][30][31][32][33][34][35][36] and disc specimen weakened by U-notch 37 are among the circular shape test samples in this regard that are able to introduce both mode I and mode II deformations in asphaltic samples.…”

Mixed mode I+II fracture parameters and cracking trajectory of heterogeneous multilayer pavement structure containing reflective crack

“…In recent years, several researchers have used different laboratory tests including the semicircular bending (SCB) test, 20–28 the dissipated creep strain energy (DCSE) test, 29 the disc‐shaped compact tension (DCT) test, 30,31 the edge notch disc bend (ENDB) test, 32–39 and so on 40,41 for investigating and analyzing the fracture behavior of asphalt mixtures. However, many of these laboratory tests cannot simulate exactly the cracking mechanism of real asphalt mixture in the field 23,36,42–53 . On the other hand, employment of laboratory samples in the real scale of pavement layers and subjected to actual traffic loading is impossible or at least is a very expensive and time‐consuming process.…”

“…However, many of these laboratory tests cannot simulate exactly the cracking mechanism of real asphalt mixture in the field. 23,36,[42][43][44][45][46][47][48][49][50][51][52][53] On the other hand, employment of laboratory samples in the real scale of pavement layers and subjected to actual traffic loading is impossible or at least is a very expensive and time-consuming process. Therefore, utilizing numerical analyses can be used as a suitable method to study the fracture behavior of the cracked asphalt pavement.…”