Analysis of different testing techniques for evaluating the adhesion of asphalt ultra-thin layers (AUTL)

Abstract

ABSTRACT The growing use of ultra-thin layers, called AUTL (Asphalt Ultra-Thin Layer), has raised the question of whether the currently used characterisation tests are equally applicable to mixes that are spread in such small thicknesses (10–20 mm). Among these tests are the shear tests mainly used for evaluating adhesion between layers. The guillotine type clamps, used in the tests such as the Leutner or any of its adaptations, can present problems when performing the test with thicknesses under 20 mm, so many regulations require minimum layer thicknesses. The aim of this study is to determine whether this type of test is still valid when one of the layers is thin or whether there are other tests that can be used in this case. For this, five different test types are considered: the usual shear test, a tensile test, an adaptation of the Fenix test, a torsion test and a fatigue test. This paper presents a description of these tests, as well as the results obtained with each of them after testing the cores extracted from a test section. The results demonstrate that all the tests can be valid and are capable of discriminating between the different tack coat dosages.