Validation of a sieve analysis procedure to quantify reclaimed asphalt pavement (RAP) binder availability

Abstract

ABSTRACT Recycled binder availability (RBA) refers to the proportion of total recycled binder that is available to blend with virgin asphalt binder and is considered an inherent property of a given reclaimed asphalt pavement (RAP) stockpile. Recycled binder contribution (RBC) is the fraction of the recycled asphalt binder that is incorporated into the virgin binder within an asphalt mixture. Binder that is inside agglomerated RAP particles that do not separate during the mixing process is ‘unavailable’. This study validates a method to quantify RBA through comparative sieve analysis of RAP and recovered RAP aggregate, testing two hypotheses: (1) RAP agglomerations preexist and don’t fully break during production, and (2) RBA measurements estimate RBC. The method was applied to nine RAP sources from four states. The innovation was verified to accurately reflect RBC in asphalt mixtures through comparative tracer-based microscopy. Results showed RBA and RBC typically between 50-60%, indicating not all recycled binder blends with virgin binder. Further analysis of mixtures fabricated with different preheating and conditioning procedures suggested that RBC doesn’t vary significantly with laboratory production conditions. Thus, RBA measurements from sieve analysis show promise in estimating RBC in asphalt mixtures across production conditions, supporting the study’s hypotheses.