Interface Bonding between Hot-Mix Asphalt and various Portland Cement Concrete Surfaces

Abstract

Interface bonding between hot-mix asphalt (HMA) overlays and portland cement concrete (PCC) pavements is one of the most significant factors affecting overlay service life. In this study, accelerated pavement testing was performed to quantify the effects of tack coat type, tack coat application rate, and PCC surface texture on the interface bonding and overlay performance. This study builds on and validates previously completed laboratory tests where an HMA overlay was placed on top of existing PCC pavement composed of various surface textures including smooth, transverse tining, and milling. Asphalt emulsion SS-1hP and cutback asphalt RC-70 were applied at three residual application rates, 0.02, 0.04, and 0.09 gal/yd²; asphalt binder PG 64-22 was applied at 0.04 gal/yd². In total, 25 test sections were constructed and loaded with the accelerated transportation loading assembly at the centerline. The tensile strains at the bottom of HMA, to quantify potential interface slippage, were measured for selective sections, and primary HMA rutting was analyzed for all sections. The study validated laboratory-determined optimum tack coat application rate, which provided the lowest interface strain and surface rutting in the field. Both PG 64-22 and SS-1hP showed better rutting resistance than RC-70. Milled PCC surface provided lower rutting than transverse-tined and smooth surfaces. The study also showed that PCC cleaning methods played an important role in the HMA–PCC interface bonding.