Estimating the Effect of Recycled Asphalt Pavements and Asphalt Shingles on Fresh Binder, Low-Temperature Properties without Extraction and Recovery

Abstract

The use of recycled asphalt pavements (RAP) and recycled asphalt shingles (RAS) as components of new asphalt mixes is expected to reduce construction costs, protect the environment, and conserve dwindling natural resources. However, the use of high percentages of RAP and RAS requires mix adjustments to accommodate the stiffer binder, which in turn requires quantification of the effect of the RAP and RAS binder on the fresh binder used in the mixture. Current methods for such estimates are performed on the basis of either chemical extraction and recovery of the binder or backcalculation from gyratory compacted samples. The former is not desirable because of the unknown effects of the chemical solvents on the binder, and the latter requires extensive laboratory work and resources. This paper modifies the analysis procedure for estimating the low-temperature properties of RAP binder by means of testing mortars and binders in the recently developed bending beam rheometer. The modified testing procedure was verified by testing artificial RAP materials, and found capable of estimating low-temperature grade of aged binder within 1°C of the known grade. Furthermore, the application of the procedure to RAS allowed for the introduction of the basis for the development of RAP and RAS blending charts to estimate the final grade of blended binder in mixtures. The feasibility of extending the procedure to study the effect of RAP and RAS on binder fracture properties is also presented in this paper.