Effective parameters on interface failure in a geocomposite reinforced multilayered asphalt system

Abstract

Application of geosynthetics is known as an effective way to reduce and delay reflective cracks. Although these materials can improve pavement resistance against reflective cracking, they can reduce shear bonding between the overlay and the old pavement. Lack of this resistance can cause some defects, especially in zones in which cars accelerate, decelerate or turn. There are many parameters affecting the quality of shear bonding between layers. In this research, a double shear bonding test denoted as Amirkabir University of Technology Shear Lab Tester was developed and was used for conducting dynamic shear loading experiments on geocomposite reinforced specimens. In order to simulate the weight of passing vehicles, a normal loading system was designed and added to the double shear test device. This normal loading system applies constant stiffness on the specimen, thus simulating real conditions with high fidelity. Seven factors, namely temperature, tack-coat application rate, tack-coat penetration value, geocomposite mesh size, mean texture depth of old pavement surface, loading amount and loading frequency were selected, based on the literature review. The experimental design was Taguchi L16 (2*3 4*4) orthogonal. Graphs of values of the shear stiffness modulus versus number of loading cycles have shown that increasing the number of loading cycles applied on the specimen results in a decline in the interface shear stiffness that occurs in three distinct stages. Furthermore, ANOVA analysis was performed, focusing on interlayer shear stiffness, interlayer failure levels and number of loading cycles required to reach these failure levels. In addition, within the studied range of factors, among the examined parameters, the temperature and tack-coat application rate were found to be the most influential on the initial interlayer shear stiffness. Moreover, the application of normal load with normal stiffness was shown to noticeably augment the geocomposite mesh size effectiveness. Temperature, followed by geocomposite grid size, emerged as the most important parameter for determining the number of loading cycles required to reach 10%, 30%, 50% and 70% of the initial shear stiffness. On the other hand, the number of loading cycles required for shear stiffness reduction was primarily affected by the tack-coat application rate.