The influence of warm mix asphalt on binders in mixes that contain recycled asphalt materials

Rheological effects of warm mix asphalt (WMA) additives have been carefully studied in the laboratory since their introduction. Research has shown that reduced plant temperatures decrease the aging of the asphalt binder. It is important to determine if the reduction in the asphalt binder grade is still detectable after in-service aging. Each pavement represents one of the three predominate types of WMA technologies: chemical modifiers, wax modifiers and a foaming process. All mixes in the study included RAP and some with recycled asphalt shingles (RAS). The performance grade (PG) was determined for virgin binders. Field-cores were measured for density. Binder from cores was extracted and recovered to compare between the HMA and WMA. Field performance surveys compared HMA and WMA test sections. Findings show little evidence to suggest WMA facilitates the incorporation of higher amounts of recycled asphalt materials. The recycled binder had a larger influence on binder properties compared to WMA additives. Performance surveys for HMA and WMA mixtures were comparable. Recovered binder from field cores showed similar performance in both HMA and WMA binders. All three mixtures comparing WMA and HMA mixes show evidence that the reduced production temperatures do not have long term impacts on the binder properties.