Analysis of the Draft European Standard on Interlayer Bonding and Understanding of the Influencing Factors

The pavement lifetime depends in particular on the presence and quality of the tack coat at the interfaces. Various methods are proposed in the draft European project 12697-48:2014. The USIRF, Professional Union of the French Road Industries, by means of two internships (2012–2014) supervised by the ESTP and ENSAM, two French engineering schools, suggested analyzing the relevance of the tests of the draft standard, by realizing a literature review but also a laboratory work. The use of experimental design relieved the tests number. The tests were conducted within the Scientific Campus of Colas on bi-layer cores. The pavement structure was made up of two asphalt layers bonded with a tack coat (French BBSG 0/10 and GB 0/14). Five main factors were taken into account in experimental design: temperature, loading rate, density of the two layers, and type of emulsion, with 2 interactions. The three principal tests methods proposed by the draft standard were applied: Torque Bond Test (TBT), Shear Bond Test (SBT), Tensile Adhesion Test (TAT). The results turn out complementary between them, even sometimes contradictory, with not always the same evolution. Consequently, we have numerous questioning on the relevance of the tests proposed by the draft standard: can we select one and which? Besides, we have noticed feasibility and security problems on the manual Torque bond test described by the standard. In addition, mechanical Torque bond tests were led, with more reliable results.