Method to determine full work of fracture from disk shaped compact tension tests on hot-mix asphalt

Abstract

Fatigue cracking is an important mode of failure in hot-mix asphalt (HMA). As part of the revision of the South African pavement design method (SAPDM) a need was identified to assess the fracture toughness of HMA in terms of fracture energy. The disk shaped compact tension test (DSCTT) was selected to experimentally determine the fracture energy. The paper contains the results of an initial round of testing aimed at assessing the suitability of the DSCTT procedure for use in the SAPDM project. The study found that when the DSCTT is performed in accordance with the ASTM test method, a portion of the work of fracture will not be recorded. A methodology is proposed to model the missing part of the exponential tail of the DSCTT load displacement curve and in doing so obtain a more precise measure of the work of fracture and therefore the fracture energy. Numerical simulation using the embedded discontinuity method shows that the value for fracture energy obtained from the DSCTT can be used to accurately reproduce the fracture behaviour of the material.