Investigation of the Tensile Behavior of Recycled Asphalts in the Small-Strain Domain with the Grid Method
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Under mechanical loading, asphalt mixtures exhibit in their bulk heterogeneous strain fields characterized by localized gradients concentrated within the binder. Measuring such fields constitutes a challenge for the full-field measurement methods currently used in the experimental mechanics community. This is particularly true when the objective is to measure strains in the linear viscoelastic domain, which is characterized by low strain levels (about some 200 με). In the present study, the strain distribution is measured on the surface of several recycled asphalt pavements (RAP) subjected to direct tensile tests. Four asphalt mixtures incorporating respectively 0%, 20%, 40% and 100% of RAP are studied. The tests are performed using a servo-controlled machine for rheological tests (MAER) and the local strain fields are measured using the Grid Method (GM). Out-of-Plane Motions (OPM) and camera noise are the main causes of disturbance that significantly affect the strain measurements. A method is proposed here to compensate the OPM. It is specially dedicated to bituminous mixtures. Sensor noise is filtered over time to improve the measurement resolution. Obtained results indicate that such compensations allow the use of GM to obtain quantitative measurements of the asphalt deformation in the small-strain domain. Finally, the behavior of the different samples are compared and the effect of RAP inclusion on the local strain distribution is observed and characterized.
KeywordsRecycled asphalt Out-of-plane motions Full-field measurement Grid method Strain fields
The Auvergne Regional Council- France is gratefully acknowledged for providing the financial support of this study. The authors also thank Eric Crégut for his assistance in the preparation of the samples.
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