Chapter 7 Studying with a Full-Field Measurement Technique the Local Response of Asphalt Specimens Subjected to Freeze-Thaw Cycles M. C. Teguedi, B. Blaysat, E. Toussaint, S. Moreira, S. Liandrat, and M. Grédiac Abstract Asphalt is a strongly heterogeneous material, whose global thermo-mechanical behavior is generally studied at a large spatial scale. Observing the local strain fields which occur between aggregates and mastic (i.e., asphalt binder C filler) is however crucial to understand the phenomena that influence the global response of such materials, and then better design them. In this study, full-field measurements were used to investigate the difference in behavior between various types of asphalt containing Recycled Asphalt Pavement (RAP). We focused here on their response when they were subjected to freeze-thaw cycles. The local contraction/expansion of the specimens subjected to various cooling/heating phases was observed with the grid method. The strain distribution has been found to be very heterogeneous because of the difference in coefficient of thermal expansion between aggregates and mastic. The influence of the percentage of RAP on the global response of the specimen is observed and discussed. Keywords Recycled Asphalt • Thermal contraction/expansion • Strain field • Freeze-thaw • Grid method • Digital image correlation In cold regions, pavements suffer from the thermal cracking caused by the contraction and expansion of asphalt under temperature changes. The thermal behavior of asphalt at the macroscopic scale has been widely studied using testing devices such as the Asphalt Thermal Cracking Analyzer (ATCA) [1] and the Asphalt Concrete Cracking Device (ACCD) [2]. However, since low temperature damages are initiated in the internal structure of asphalt mixtures, understanding the thermal response of asphalt components (bitumen and aggregates) is of great practical importance to have a better understanding of the overall thermal response of pavements. The major problem is however to measure the local thermal response of these materials. Full-field measurement techniques, which have now widely spread in experimental mechanics, are useful to have a better understanding of the asphalt behavior under thermal loadings. In recent years, these methods have become major tools to inspect and characterize the mechanical response of such materials. The main full-field measurement methods that are used by the pavement community are the digital image correlation (DIC) [3–5] and more recently the grid method (GM) [6, 7]. This last technique was used here because it exhibits a good compromise between spatial resolution and measurement resolution [8], which is crucial here, the material under investigation being highly heterogeneous. Till now, the application of such measurement techniques for the characterization of asphalt was limited to their mechanical response, and few emphasis has been placed on the investigation of their thermal response. In this study, four Hot Mixtures Asphalt (HMA) specimens with 0%, 20%, 40% and 100% of RAP (Recycled Asphalt Pavement) content were considered. These materials were used in a previous study, which was devoted to the characterization of the effect of RAP on the local mechanical behavior of recycled asphalt pavements [6]. These RAP materials are composed of granite, basalt and gneiss. The virgin materials are constituted from limestone aggregates and a virgin bituminous binder. Freeze-thaw tests were carried out on these materials. They were performed in a climate chamber at a temperature range of [ 10 ıC20 ıC]. At the global scale, the specimens exhibited an anisotropic behavior along both the vertical and horizontal directions. The comparison of the global strain-temperature curves showed that the inclusion of 100% RAP resulted in an increase of the Coefficient of Thermal Contraction (CTC) of the specimen. Typical examples of the displacement fields M.C. Teguedi • B. Blaysat • E. Toussaint • M. Grédiac ( ) Université Clermont Auvergne, Institut Pascal, BP 10448, 63000, Clermont-Ferrand, France CNRS, UMR 6602, Institut Pascal, 63171, Aubière, France e-mail: michel.grediac@univ-bpclermont.fr S. Moreira • S. Liandrat Département Laboratoire de Clermont-Ferrand (CEREMA, DterCE), Clermont-Ferrand, France © The Society for Experimental Mechanics, Inc. 2018 L. Lamberti et al. (eds.), Advancement of Optical Methods in Experimental Mechanics, Volume 3, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-63028-1_7 43
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