Modelling of viscoelastic properties and crack growth in bituminous mixtures: Application to the simulation of crack growth in semi-circular samples subjected to oxidative ageing

Abstract

This paper presents the development of a mechanical crack propagation model coupling viscoelasticity and the extended Griffith’s criterion to the dissipative medium. The applications are related to the study of mode I cracking of bituminous materials subjected to loading rates under intermediate temperature condition and long term ageing duration. The viscoelastic behaviour of these materials based on a Generalized Maxwell (GM) model is presented and a discretized form of the state equation based on the exponential algorithm is given. The simulation of the complex modulus test is used to validate the proposed discretized law. Then, the thermodynamic framework of the Griffith criterion extended to the GM’s model is revisited. A crack growth criterion is derived involving the viscoelastic energy release rate (Gϑ) as a thermodynamic driving force capped by a resistance strength (R-curve). Analytical and numerical implementations of the Gϑ on a semi-circular bending geometry (SCB) are presented. SCB fracture tests following a standard experimental protocol are then simulated. The resistance strength parameters taking into account the fracture process zone effect are identified by an optimization technique resulting in a good agreement between the test results and the numerical simulations. This study demonstrates that the proposed approach can account for the ductile fracture properties of bituminous mixes.