Influence of extended aging on the properties of asphalt composites produced using hot and warm mix methods

Abstract

Fatigue cracking resistance of asphalt binders and composites is influenced by the presence of modifiers and aging conditions. This paper presents the findings from a study conducted to evaluate the fatigue cracking resistance of asphalt mortars or fine aggregate matrix (FAM) as influenced by two factors: (i) the presence of warm mix additives with reduced short-term aging temperatures and (ii) the influence of long-term aging of the mix. Combinations of two binders with four different warm mix additives and one aggregate type were used to evaluate the first factor. The second factor was evaluated by subjecting the loose mix to extended aging in an environmental room at high temperatures. X-ray CT analysis were conducted on a limited number of samples compacted before and after extended aging to ensure that the internal structure of the specimen did not change significantly and the differences in performance could be attributed to aging of the mix. A dynamic mechanical analyzer (DMA) was used to evaluate the fatigue cracking resistance of the FAM test specimens. The stiffness and the fatigue cracking resistance of the FAM specimens were compared before and after long-term aging. Results indicate that the specific binder–additive pair governed the influence of the warm mix additive on the fatigue cracking life of the FAM specimens. More importantly, results also indicate that the rank order of the short-term aged mixtures, in terms of their fatigue cracking resistance, did not change significantly after long-term aging. The ranking of fatigue cracking resistance of short-term aged specimens using different binders correlated well with the ranking of fatigue cracking resistance of long-term aged specimens.