Effects of Shear Bond Characteristics of Tack Coats on Pavement Performance at the Interface

Abstract

A finite element (FE) approach was used in a study to investigate the effects of interface shear bond characteristics of tack coats on pavement response at the interface. A two-dimensional FE modeling approach incorporated laboratory-measured bond characteristics of tack coats to describe the constitutive behavior at the interface. Two pavement structures typically used in Louisiana for low and medium traffic levels were simulated. The Louisiana interlayer shear strength tester was used to test three types of emulsified tack coat materials—CRS-1, SS-1h, and trackless—and a PG 64-22 asphalt binder at three residual application rates, 0.14, 0.28, and 0.70 l/m2 (0.031, 0.062, and 0.155 gsy). From the results of the FE simulation analysis, it was determined that the performance of tack coat materials at the interface was primarily dictated by the pavement structure with no pronounced change in the field stresses from one tack coat material to another. In addition, the influence of tack coat material type and application rate became more relevant in thin pavements and less dominant in thick pavement structures. For the thin structure considered in the study, it was determined that the majority of tack coat materials and application rates would experience fatigue damage at the interface. The minimum laboratory-measured interface shear strength to provide acceptable fatigue performance at the interface was 190 kPa (28 psi). For the thick structure considered in the study, the majority of the tack coat material types and application rates performed satisfactorily against fatigue damage at the interface. The minimum laboratory-measured interface shear strength to provide acceptable fatigue performance at the interface was 128 kPa (19 psi).