Effect of pavement type on overlay roughness progression

This paper investigates the impact of overlay type (asphalt and concrete) on the progression of pavement roughness as described by the international roughness index (IRI). Pavement roughness is defined as deformities or irregularities found at the pavement surface affecting the smoothness of a ride. Both overlays in this study are asphalt: one placed on asphalt paved roads and one placed on top of prior concrete pavement. Data were collected from nine states using data in the Long-Term Pavement Performance database (GPS6 and GPS7). Only U.S. states and Canadian provinces that have both GPS6 and GPS7 sections are considered for analysis. Pavement factors (overlay age, temperature, freezing index, and overlay thickness) that significantly impact overlay performance in U.S. and Canadian environments have been used for analysis. Multivariate regression analysis was used to compare the effect of key variables (age, temperature, freezing index, and surface thickness) on IRI. Results show that there is a significant difference between overlay types in terms of the effect of key variables on IRI. Asphalt on concrete overlay has a significantly better IRI performance in terms of age, temperature, and surface thickness. Asphalt on asphalt overlay has a significantly better performance in terms of freezing index. This suggests that when age, temperature, and surface thickness are considered, asphalt on concrete provides a better IRI. Asphalt on asphalt provides a better IRI for freezing index.