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The stress-strain relationship of materials is used to predict their performance during service. This paper presents an evaluation of asphalt concrete modes of failure and describes the stress-strain relationship that governs the material beyond the limit of elasticity. The relationship of stress-strain is identical to that of cement concrete in compression. The experiments used short term static compression loading on cylindrical and prismatic asphalt concrete specimens. The effects of mixture types, specimen shape, height, temperature, binder type and testing orientation were investigated. The key parameters of the stress-strain curve were determined and used in assessing the failure mode, were: unconfined compressive strength, the strain at peak stress, initial tangent modulus and fracture energy. The tests revealed that cube specimens tested parallel to the direction compacted, achieved higher compressive strength than specimens tested perpendicular to the direction compacted. Similar strain at peak stress was obtained for both loading directions. An increase in height in cylindrical specimens, resulted in a decrease in compressive strength and strain at peak stress. Cylindrical specimens had greater stiffness than prismatic specimens with similar aspect ratios. Specimens at higher temperatures attained lower compressive strength. The study also showed that temperature has significant influence on the initial tangent modulus and fracture energy. The higher the temperature, the lower the initial tangent modulus and the fracture energy. There were significant changes in the peak stress and strains between the asphalt concrete mix types. The parameters derived can and have been used for inputs in finite element programs to model the laboratory and field behavior of different asphalt concrete mixtures used in pavement structures.

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