Contribution of Interface Fracture Mechanism on Fracture Propagation Trajectory of Heterogeneous Asphalt Composites

Abstract

Asphalt mixture is a type of textured composite material made of aggregates and mastic part. Overall strength and failure behavior in such materials depends on the texture or heterogeneity of the mixture. In particular, the crack growth mechanism from the tip of the pre-crack is significantly affected by the texture of the asphalt composite and environmental conditions. The crack can extend through the soft mastic, tight aggregates or interface of the mastic/aggregates. In this research, by performing some fracture tests on a typical asphalt mixture with different test specimens under mode I, mixed mode I/II and mixed mode I/III, the fracture resistance and trajectory of propagating crack is studied at two low and medium temperatures (i.e., −15 and +15 °C). The load bearing capacity and the fracture resistance of the tested asphalt samples increases by decreasing the temperature. It is also shown that a significant part of fracture plane passes through the soft mastic and boundary of aggregates (i.e., the interface of aggregates and mastic) and only about 10–15% of the fracture surface of the propagating crack passes via the tight aggregates by breaking them. This percentage decreases for mode II and III loading conditions and higher testing temperatures. Compared to brittle and isotropic materials, the fracture path of the asphalt mixture shows more deviation, and this deviation increases for those mixtures containing coarser aggregates in the ligament and tested under medium temperature conditions.

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

“…where P is the applied load and Y I is the mode I geometry factor that is a function of the specimen geometry (i.e., a/R or a/t) and loading conditions (i.e., S/R or S/L) of the ENDB, SCB, SENB and ENDC specimens [31,32,[58][59][60][61][62]. The corresponding values of these geometry factors can be determined using finite element analysis.…”

“…Furthermore, all of the mentioned Fracture toughness (K Ic ) can be determined experimentally using suitable specimens and relevant test methods. Among the test configurations available for obtaining the K Ic value of asphalt mixtures, the following methods have received much attention by the researchers: (i) Edge cracked rectangular beam loaded with three-point or four-point bending [1,6,9,10,12]; (ii) Edge cracked circular compact tension specimen by pin loading (DCT) [1,2,13]; (iii) Edge cracked semi-circular specimen loaded with symmetric three-point bending (SCB) [4,6,7,[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]; (iv) Center cracked Brazilian disc specimen loaded with diametral compression (BD) [30,31]; (v) Edge cracked disc specimen loaded with diametral compression (ENDC) [32,33]; (vi) Edge cracked disc specimen subjected to three-point bending (ENDB) [34][35][36][37][38][39][40][41][42];…”

Effect of Aging and Moisture Damage on Fatigue Cracking Properties in Asphalt Mixtures

“…At a specific temperature, the value of the transfer coefficient becomes zero and the temperature at this time is the reference temperature that can be determined at any experimental temperature; however, an intermediate value is generally used. This logarithmic shift factor is fitted by Equation ( 3) and is used to determine the elastic modulus at any temperature and frequency using Equation (2) in combination with the coefficient determined in Equation (3).…”

“…Various indoor test methods have been developed to simulate the properties of asphalt mixtures for moisture damage. In addition, the effect of aging and also cracking study of asphaltic mixtures and bituminous materials has also been investigated in recent years [3][4][5][6][7]. According to Brown et al (2000), the tensile strength ratio (TSR) of the asphalt mixture before and after moisture damage prescribed in AASHTO T 283 is the most effective method for understanding the sensitivity of asphalt mixture to moisture damage, which is a representative and simple test method generally applied natively and in other countries [8].…”

Crack resistance of fiber‐reinforced asphalt mixtures: Effect of test specimen and test condition

“…Studies on fracture behavior of materials need using suitable laboratory test specimens, and the selection of specimen and test method depends on the material type and manufacturing processes 22–24 . For geomaterials such as rock, cement concrete, or asphalt, disc‐shaped specimens are among the reasonable choices because of the ease of extraction from the cylindrical cores 25–27 …”