Keys to Managing RAP Variability

This article provides guidelines developed by the National Asphalt Pavement Association for best practices in processing recycled asphalt pavement from multiple sources, and ways to achieve consistent reclaimed asphalt pavement (RAP) products that can be used in new mixes at higher percentages. Variability in RAP has led many contractors to limit the amount of RAP in asphalt mixes because there is such variability in these materials. The author provides eight general principles for achieving consistent RAP products that use higher percentages of RAP in new mixes. These include: avoiding contamination by keeping deleterious materials out of RAP stockpiles; mixing as you feed, not over-crushing RAP, fractionating RAP to provide greater flexibility in designing mixes; ceasing processing during rain; blending when moving, minimizing moisture in RAP stockpiles by covering it; and, testing and analyzing RAP as the stockpile is being built at its final location.