Laboratory and Full Scale Evaluation of Recycled and Warm Mix Asphalts

Abstract

This study evaluated the cracking characteristics of asphalt materials containing RAP/RAS and prepared with WMA technology. Tests were performed in the laboratory and at a full-scale testing facility. Ten test lanes were built at FHWA’s Accelerated Loading Facility (ALF). The experimental design included three RAP percentages up to 44% by weight (40% recycled binder ratio, RBR), two WMA technologies (water foaming and chemical additive), one RAS percentage with 20% RBR, and two different virgin binders (PG 58-28 and PG 64- 22). Specimens prepared from loose mixes sampled from the construction and field cores sampled at different times were evaluated using the direct tension monotonic test. Performance grade and cracking resistance of asphalt binders recovered from tested loose mix and field cores were determined. The laboratory monotonic testing results were compared to and statistically correlated to the ALF field cracking performance. Experimental results from both laboratory mix and binder tests capture the oxidative aging that occurs with time in the top lift. Aging observed in the bottom lift of the asphalt pavement was considerably less. One of the mechanical parameters developed from the mix monotonic test closely correlated with the binder tolerance strain obtained from the binder DENT test. Long- term oven aging aged the mix significantly more severely than was observed in threeyear old ALF sections. Testing of ALF materials shows that the mixtures with 40% RAP RBR or 20% RAS RBR and stiff binder exhibited the worst cracking performance. A softer PG grade was found to be effective at improving the performance for 40% RAP RBR mixes but ineffective at improving the performance of 20% RAS RBR mix. No difference in field performance was observed between the HMA and WMA mixtures having the same mix design. Statistical analysis indicated a strong correlation between the direct tension monotonic mix test and ALF field testing in terms of evaluating the cracking