Investigating Reflective Cracking Mechanisms in Grid-Reinforced Asphalt Specimens

The main purpose of this research was to examine the effects of interfacial conditions on the reflective cracking-related failure mechanisms of fiberglass grid-reinforced asphalt concrete beams using four-point bending notched beam fatigue tests (NBFTs). This study also aimed to determine whether conventional stiffness-based failure criteria could be used to rank the performance of grid-reinforced beam specimens. For these objectives to be fulfilled, asphalt concrete interfaces were reinforced with two types of fiberglass grid, G12.5 and G25, with and without a tack coat. The tack coats used in this study were PG 64-22 asphalt binder, SS-1 emulsion, and a highly polymer-modified tack coat. Also, two types of mixtures, with 9.5-mm and 12.5-mm nominal maximum aggregate sizes, were included in the testing plan. The beam fatigue tests were conducted at 20 degrees C, and digital image correlation was used to measure the displacements and strains. The results suggest that different interlayer conditions do not reflect a unique failure mechanism, and, therefore, traditional stiffness-based failure criteria can be misleading. Thus all mechanisms, including damage within the asphalt layers and along the interface, that result in weakening the structural integrity of the layered samples must be considered when the performance of reinforced beams under NBFT loading is evaluated. The results indicate that grid-reinforced specimens outperform nonreinforced specimens and that the presence of a high-quality tack coat extends the fatigue life of grid-reinforced specimens.