Use of phase angle in lieu of critical crack tip opening displacement for asphalt binder specification

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Khusainov, Emil
materials chemistry , asphalt binder specification , polymer chemistry , asphalt binder , specification grading , limiting phase angle temperature , Crack Tip Opening Displacement (CTOD)
The road pavement sector in countries with cold climates such as Canada currently faces a significant problem with the construction of asphalts demonstrating less than optimal long-term performance. Therefore, attention should be paid to the asphalt binder acceptance criteria used. This study considers how phase angle specification limits can be used in lieu of Critical Crack Tip Opening Displacement (CTOD) as a more practical asphalt binder acceptance property. Two sets of binders were tested using the Dynamic Shear Rheometer to determine the resistance to fatigue cracking, permanent deformation, performance at high, intermediate and low temperatures. The Double-Edge-Notched Tension (DENT) test was performed to measure the ductile strain tolerance in the presence of critical tensile stresses. Subsequently, DENT parameters of binders were compared with limiting temperatures where the phase angle reached either 30° or 45° to check for a possible correlation. The results showed promising ability of 30° phase angle temperature to evaluate the strain tolerance of asphalt binder. These results showed that 30° phase angle temperature is slightly more useful than 45° phase angle temperature to evaluate the strain tolerance of asphalt binder as well as the high temperature performance grade is very sensitive to additives and is more informative for asphalt long-term behavior prediction than intermediate and low temperature performance grades.
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