Relationships between low temperature properties of asphalt binders
Résumé
Cracking in asphalt mixes is highly influenced by binder properties. Current specifications for low temperature cracking resistance are based on empirical tests or tests involving linear viscoelasticity. Although these standard characteristics may work for conventional binders, they cannot be applied on all asphalts. Using the three points bending test (TPBT) on pre-notched asphalt beams appears to be a solution in that context. This paper presents a comparison between low temperature properties, obtained from Bending Beam Rheometer (BBR), complex modulus, TPBT and Fraass tests. Eight asphalt binders and the resulting ones from aging process were studied. The results showed that BBR and complex modulus give similar information about low temperature binder’s linear viscoelasticity (strongly correlated limiting temperatures obtained using both methods). Fracture and linear viscoelastic properties rank asphalt binders differently, although they may present some correlation. Intermediate coefficients of determination between limiting temperatures obtained using both criteria lead to the conclusion that linear viscoelasticity aspects are not the only variables controlling cracking behaviour. Indeed, they play an important role in crack initiation and growth increasing or decreasing stresses, but they do not determine fracture properties. Other phenomena linked to the microstructure behaviour under high strain are involved in the cracking process.
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