Aging effect on combined mode fracture resistance of bitumen

Abstract

Crack growth behaviour of aged and unaged 30/40 asphalt binder at subzero temperature was studied both experimentally and theoretically using a test sample called inclined notched bend beam specimen. A series of fracture tests were conducted on this specimen at two subzero temperatures and different combinations of modes I and II. The fracture toughness of tested asphalt binder was significantly dependent on the aging condition such that the load‐carrying capacity of aged bitumen was up to 60% less than the corresponding fracture resistance of unaged bitumen. Moreover, the effective fracture resistance value of tested binder was reduced by increasing the contribution of mode II and also decreasing the test temperature. The obtained experimental results for both binder types were also evaluated theoretically using a stress base crack growth theory.

Specimen type effect on measured low‐temperature fracture toughness of asphalt concrete

“…For example, additives such as anti-stripping agent, polyphosphoric acid, Fischer-Tropsch (FT) paraffin wax (Sasobit), crumb rubber, styrene-butadiene-styrene and low-density polyethylene (LDPE) are some of the used additive materials for improving the mechanical and performance characteristics of base bitumen. [44][45][46][47][48][49][50][51][52] These additives are mixed with the binder at a specific temperature and with specific mixing procedure. Then, the F I G U R E 4 Variations of mode I geometry factor for different locations of crack front in the analysed three-dimensional specimens: (a) SCB, (b) ENDB and (c) ENDC.…”

KIcandKIIcmeasurement for hot mix asphalt mixtures at low temperature: Experimental and theoretical study using the semicircular bend specimen with different thicknesses

“…Some test specimens usually in the shape of circular discs including diametral compact-tension (DCT) specimen, [1][2][3][4] centre cracked Brazilian disc specimen, 5 semicircular bend (SCB) specimen, [6][7][8][9][10][11][12][13][14][15][16][17][18][19] edge notch disc bend (ENDB) specimen [20][21][22][23][24][25][26] and edge notch disc diametral compression (ENDC) specimen 27,28 are usually used for conducting the fracture toughness experiments on asphalt mixtures. In addition, beam shape specimens such as rectangular beam specimen containing an edge crack and subjected to three-point bending (TPB) or four-point bending (FPB) [29][30][31][32][33][34][35] or wedge-splitting cube (WSC) 36,37 samples are among the other miscellaneous fracture test specimens employed by the asphalt and bituminous researchers. The above-mentioned test methods were mostly used earlier for performing the pure mode I fracture toughness (K Ic ) experiments on asphalt concrete materials.…”

An extended maximum tangential strain energy density criterion considering T‐stress for combined mode I–III brittle fracture

“…A great quantity of research results showed that the brittle fracture characteristic and the crack tip plastic zone of cracked materials under combined mode I-II loading are greatly influenced by the T-stress near the crack tip. 16,[31][32][33][34][35][36] The T-stress, which is the first nonsingular constant term, has been considered to be another important fracture parameter in fracture mechanics, and it has been extensively adopted to improve the prediction accuracy of the conventional fracture criteria. 16,37,38 Some frequently used fracture criteria considering the T-stress are the generalized MTS (GMTS) criterion, 1,14 generalized MERR criterion, 21 generalized SED criterion, 18 extended MTSN criterion 15 and so forth.…”

“…However, the nonsingular terms of Williams' series expansion as well as SIFs can also play a significant role in the fracture process. A great quantity of research results showed that the brittle fracture characteristic and the crack tip plastic zone of cracked materials under combined mode I–II loading are greatly influenced by the T‐stress near the crack tip 16,31–36 . The T‐stress, which is the first nonsingular constant term, has been considered to be another important fracture parameter in fracture mechanics, and it has been extensively adopted to improve the prediction accuracy of the conventional fracture criteria 16,37,38 .…”