FRACTURE TOUGHNESS OF ASPHALT IN THE SEMI-CIRCULAR BEND TEST

Abstract

The semi-circular bend test is investigated for its suitability to determine the critical mode I stress intensity factor, or fracture toughness, of asphalt. Seven types of asphalt mixture were investigated. Indirect tensile tests were conducted, on each mixture, to compare the indirect tensile strength to the apparent fracture toughness, in order to test the hypothesis that the apparent fracture toughness can be interpreted as the tensile strength of a notched test specimen. The advantage of the use of a notched specimen is that the scatter on the tensile strength is strongly reduced. It is found that the apparent fracture toughness depends more strongly on the specimen diameter than on the specimen thickness. The apparent fracture toughness is fairly independent of the specimen diameter, for a deformation rate of 0.005 mm/s, provided the specimen diameter is greater than 150 mm. Similarly, the apparent fracture toughness is almost indpendent of the specimen diameter, for a deformation rate of 0.05 mm/s, provided the specimen diameter is greater than 220 mm. For practical purposes, this dependence on the specimen geometry seems sufficiently weak, to justify the apparent fracture toughness being considered as a valid fracture toughness, up to test temperatures little lower than 15 degrees C. For the covering abstract see ITRD E107185.