The effects of using reclaimed asphalt pavements (RAP) on the long-term performance of asphalt concrete overlays

• RAP performance is affected by asphalt overlay thickness and pre-treatment intensity.
• Virgin asphalt outperforms RAP in crack resistance in thin and less treated overlay.
• Virgin asphalt outperforms RAP in rutting resistance in thin and less treated overlay.
• Virgin asphalt outperforms RAP in smoothness in thin and less treated overlay.
• RAP outperforms virgin asphalt in rutting resistance in thick and pre-treated overlay.
• RAP outperforms virgin asphalt in smoothness in thick and pre-treated overlay.
• RAP performance is driven by its reduced crack resistance and increased stiffness.

The long-term performance of asphalt concrete (AC) overlays using mixtures containing reclaimed asphalt pavements (RAP) is compared with the performance of overlays using virgin mixtures. Data from 18 sites of the long-term pavement performance (LTPP) program are used for analysis. Each site consists of 8 side-by-side experimental sections that vary in overlay thickness and pre-overlay treatment method. The selected performance indicators include fatigue cracking, longitudinal cracking, transverse cracking, rutting, and roughness. Explorative data analysis, non-parametric survival analysis, and pair-t tests are used to compare possible performance differences. The analysis results suggest that there are interactive effects between the use of RAP-containing mixtures, overlay thickness, and pre-overlay treatment method. With relatively thin (51 mm) overlay and minimal pre-overlay treatment, undesirable performance of RAP-containing mixtures is expected. Conversely, with relatively thick (127 mm) overlay and intensive pre-overlay treatment, RAP-containing mixtures outperform virgin mixtures in rutting and roughness, without inducing additional cracking-related distresses. The field performance of RAP-containing mixtures is believed to be driven by their fundamental properties, i.e., the reduced cracking resistance and increased stiffness.