Impact on the use of Reclaimed Asphalt Shingles on mixture and recovered binder properties

The use of reclaimed asphalt shingles in bituminous mixtures has increased significantly in recent years. The information reported is part of a series of on-going investigations into the impact of RAS (Reclaimed Asphalt Shingles) and RAP (Reclaimed Asphalt Pavement) at 20% or higher levels of binder replacement. Laboratory mixtures using recovered shingle binder blended with virgin PG 58-28 and PG 52-34 were compared to mixtures produced with 20% binder replacement using reclaimed shingles. Rutting tests on unaged and Overlay Tester evaluation of mixes before and after aging at 85 degrees C were conducted. Results indicate that initial properties of RAS mixtures appear acceptable, however mixture properties after aging show severe degradation, especially with regard to fatigue for all mixtures. In 2012 a field study was initiated to evaluate mixes produced with 20% RAS and 10% RAP binder replacements. Both PG 58-28 and PG 52-34 virgin binders were used. Control sections of 20% and 31% RAP only were constructed using PG 58-28. Initial evaluation of field cores followed by laboratory aging indicate that the RAS containing mixtures' stiffness and recovered binder properties deteriorated at a faster rate than RAP only mixtures. Increases in asphaltenes with aging are highly correlated to a significant increase in the m-value failure temperature of the RAS mix recovered binders. Cores procured approximately one year after construction show substantial aging, especially of recovered binders. Also reported are data from cores removed after 2 and 3 years in service wherein the binder lifts were constructed using 20% RAS binder replacement.