Search

This study deals with the trends of fatigue life between asphalt binders and mixtures using the rate of dissipated energy change (RDEC) approach. To this end, the time sweep and four-point beam fatigue tests were utilized to assess the fatigue life of bituminous materials under different strain amplitudes. The results indicated that the RDEC approach can be utilized as asphalt mix fatigue estimation in terms of asphalt binder fatigue life. A separate unique relationship exists between the fatigue life of asphalt materials and their plateau value (PV) covering different types of materials and strain levels. Furthermore, a fatigue model was developed based solely on the PV values of asphalt binders and mixtures including all the materials and the strain levels used in this study. Results revealed conformity between time sweep and four-point beam fatigue tests in terms of RDEC methodology, and a strong correlation exists between these two fatigue tests. [ABSTRACT FROM AUTHOR]

• Load-CMOD response of asphalt mixtures is obtained by means of CZM simulations • Crack growth under mixed mode loading and viscoelastic behavior of the material. • Effects of mixture's constituents on crack propagation mechanism were investigated. This paper discusses the effects of mixed mode loading on cohesive zone parameters obtained from load-crack mouth opening displacement (CMOD) curves in asphalt mixtures at intermediate temperature. To this end, a coupled viscoelastic numerical-experimental approach has been used to capture the cohesive strength and fracture energy in the fracture process zone utilizing asymmetric semi-circular bending test. Three mode mixities (i) pure mode I (ii) mixed mode I/II with higher fraction of tensile deformation and (iii) mixed mode I/II with higher fraction of shear mode were tested and simulated. The load-CMOD curves for the investigated mode mixities and for different asphalt mixtures were predicted successfully using the aforementioned computational framework. The results showed that the binder type and loading mode have significant effect on both cohesive strength and cohesive fracture energy values of asphalt mixtures. Aggregate gradation was only effective on the cohesive strength values. Considering the interactions of the mixtures' constituents and loading, the binder- loading mode and binder-aggregate gradation were significantly effective only on cohesive fracture energy. The stiffer an asphalt binder, the more cohesive strength and fracture energy values were observed. Decreasing the distance between the supports which is equivalent to higher fraction of the shear mode in the ASCB test contributes to greater cohesive fracture energy. [ABSTRACT FROM AUTHOR]

Asphalt mixtures are time, temperature and stress dependent and categorized as viscoelastic materials. A wide range of models have been proposed to characterize the fatigue behavior of asphalt mixtures. In this study continuum damage theory is used to characterize fatigue properties of asphalt binders and their effects on mixture’s fatigue resistance. Neat, polymer modified and nanoclay modified bitumens were tested using linear amplitude sweep test. Four point bending beam fatigue tests were conducted on mixtures made with these binders at different loading rates namely 400, 600, 800 and 1000 micro-strain. Results showed that a strong correlation exists between the viscoelastic parameter of binder’s integrity and the fatigue resistance of asphalt mixtures. Furthermore, a phenomenological fatigue relationship was introduced which is a function of the strain loading of the mixture as well as the viscoelastic continuum damage properties of the binder phase in the mixture. The proposed model can be used as a surrogate to time consuming beam fatigue tests. [ABSTRACT FROM AUTHOR]