Shear Fatigue Behaviour of Tack Coats in Pavements

Abstract

International audienceFor many years, pavement engineers use mechanistic design methods that are based on algorithms to compute stresses, strains and displacements in a flexible pavement structure, or in a multi-layered structure in general. Most of these methods assume, to ease the modelling of the structure and the computation process, that the layers are fully bonded or completely unbounded to each other. Moreover, determining the effectiveness of the bonding between two layers is difficult since there is no standard test procedure to assess it. Hence, proper modelling of the interface bonding condition will represent an important finding in understanding the real behaviour of road structures, and will lead to reduce maintenance and rehabilitation costs. Asphalt emulsion is commonly used, as tack coat, to ensure the bond between two pavement layers. This study deals with an experimental characterization of interfaces shear fatigue behaviour through laboratory tests. A testing device for determining the shear fatigue behaviour is described in this paper. Shear fatigue tests, at a temperature of 5°C and a frequency of 1 Hz, were performed on asphalt concrete mix layers interface with tack coat. Samples were subjected to a cyclic symmetrical alternate shearing load at the interfaces, aiming interfaces failures within the range of 104 to 105 cycles of loading. Within this range of number of cycles, the fatigue results indicate a linear evolution of the initial shear stress half-amplitude with the decimal logarithm of the number of cycles to failure. These results are used to derive a linear fatigue law, which will serve to model the real behaviour of the interface with tack coat studied in this research

Dynamic tests on bituminous layers interface

“…The experimental program was intended to perform both fatigue and oligocyclic tests, so as to span a number of loading cycles between 10 and several millions. Diakhatè et al [10] calculated stresses at the interlayer depth using the FEM code CAST3M and observed that the interface is subjected to a repetitive symmetrical alternate shearing load. The maximum shear stress value is located at the edge of the wheel.…”

Evaluation of interlayer bonding condition on structural response characteristics of asphalt pavement using finite element analysis and full-scale field tests

“…Previous studies have determined that appropriate characterization of interlayer bonding conditions is important to accurately predict the critical responses in the pavement structure and thereby the pavement service life [4][5][6][7][8][9][10]. However, most of pavement models introduced beforehand considered two extreme interlayer conditions including full-bond condition (i.e.…”

“…stress-strain distribution) of layered flexible pavement system and thereby the pavement life based on the analytical and experimental results [4][5][6][7][8][9][10]. However, the current lack of thorough mechanistic characterization of the interlayer bonding condition that is able to capture the changes in critical responses for real pavement is probably the greatest deficiency in our ability to appropriately evaluate the effect of interlayer bonding condition for asphalt pavement.…”

“… 10. shows the transverse surface strains measured from the full-scale field tests and those predicted by the model for two interlayer bonding conditions evaluated.…”

Development of a framework for standardisation of interlayer bond of asphalt pavements

“…A simple dynamic shear test for glued three layered specimens, known as the Modified Compact Shearing (MCS) test (Millien et al, 1996, Diakhate et al, 2006 (West et al, 2005, Sholar et al, 2004, Leng et al, 2008. As depicted in Table 2.1, the devices differed in the fixing mechanism of the specimen as well as in the specimen diameter and the deformation rate of the testing of 150 mm and a width of 4.8 mm between them to hold the specimen (Sholar et al, 2004).…”