Mitigating reflective cracking with open-graded bitumen-stabilized pavement overlays: a 5-year field study

The Port of Rio Grande is located in Rio Grande do Sul, the southernmost Brazilian state. It is accessed via National Highway BR-392, paved with Portland cement concrete (PCC) in 1975. A few decades later, an asphalt concrete overlay was placed over the cracked concrete pavement. In 2019, a test section was constructed, incorporating an open-graded (permeable) cold bituminous emulsion mix (CBEM) layer over the existing pavement to mitigate reflective cracking. This study aimed to evaluate the behaviour of this bitumen-stabilized material (BSM) layer and its effectiveness in delaying crack reflection. Pavement monitoring was used to track the evolution of stiffness, rutting and cracking over five years. A mechanistic-empirical analysis was performed using the South African model for BSM, and the results were compared with field performance. The BSM layers maintained their structural capacity as an overlay on a PCC pavement, not showing excessive elastic deflection or rutting. The South African model tends to underestimate the lifespan of pavements incorporating open-graded BSM due to challenges in determining their cohesion in laboratory conditions. Surface condition analysis revealed that the asphalt mix placed over the BSM base exhibited only low-level cracking, demonstrating the effectiveness of open-graded BSM layers in mitigating reflective cracking.