Life-Cycle Impact Assessment of Recycled Pavement Projects in Virginia

About the report:

This report describes a study conducted to evaluate the performance and quantify the potential environmental benefits of recycled asphalt pavement projects completed in Virginia. The performance of the recycled projects was assessed by evaluating collected stiffness data and by the development of performance prediction models based on data obtained from the Virginia Department of Transportation (VDOT) pavement management system. Quantifying the potential environmental impacts for these projects was completed following recommendations by Harvey et al. in Pavement Life Cycle Assessment Framework. Modeling of unit processes in the various pavement life cycle stages was tailored to represent conditions and practices used in Virginia to the extent possible.

The global warming (GW) score and a Single Score Index were used to assess pavement recycling projects completed in Virginia. The study found that approximately 98% of the total GW score result came from pavement smoothness during the use stage. During the cradle-to-laid (material production, transportation, and construction) stage, the results showed that pavement recycling projects used for interstate reconstruction and primary route restorative maintenance were more environmentally friendly—as they yielded lower GW scores—compared to the conventional approaches. The results found that full depth reclamation (FDR) projects used as reconstruction on primary routes sometimes had a higher GW score compared to conventional projects, especially in instances when cement was used as a stabilizing agent (cement production at the plants is associated with high greenhouse gas emissions). When considering the entire life cycle, most of the GW score impacts came from the use stage.

The results of the structural evaluation showed that there were no large changes in the stiffness of the recycled layers for FDR projects when comparing data from 36-month and 10-year testing periods. The predicted functional service life of all recycling projects ranged from 6 to more than 30 years using thresholds based on either ride quality or a distress index. For FDR projects, cement-stabilized projects were generally predicted to last longer when compared to the asphalt-stabilized projects.

The study recommends that VDOT consider reoccurring structural evaluation of all completed pavement recycling projects to better evaluate the trends observed in this report. To reduce environmental impacts, VDOT should encourage (or even incentivize) practices that improve the initial pavement smoothness for recycling projects and use structural designs that are expected to have a low annual rate of deterioration. To better account for the actual deterioration of pavement recycling projects with the agency pavement management system, VDOT should develop a set of recycling-specific deterioration models to better reflect their anticipated longer service lives. Finally, VDOT should develop a framework to implement life cycle assessment practices to complement the current selection and design process, for pavement maintenance and rehabilitation projects, that will result in reduced environmental impacts.

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