Mechanistic performance of asphalt-concrete mixture incorporating coarse recycled concrete aggregate

The mechanistic performance of hybrid asphalt-concrete mixture incorporating coarse recycled concrete aggregate (RCA) was investigated. The hybrid mixture (W3B-RCA-C37) and control mixture (W3B-granite) were evaluated by the Marshall mix design method to determine their optimum asphalt content. Both W3B-RCA-C37 and W3B-granite mixtures had similar optimum asphalt content. However, volumetric properties (voids in total mix, voids filled by asphalt, and voids of mineral aggregate) of W3B-RCA-C37 mixture at its optimum asphalt content were lower than that of W3B-granite mixture. The Marshall stability, resilient modulus, and creep resistance of W3B-RCA-C37 mixture were higher than that of W3B-granite mixture, but it was more susceptible to moisture damage. The substitution of coarse RCA affected the mixture's performance in several ways. Equivalent mass substitution of the aggregate resulted in relatively larger RCA volume per unit mass of the mixtures. Friable RCA induced greater aggregate breakages; broken aggregates may easily reorientate and fill available space in the mixture, resulting in a lesser space for air voids and effective asphalt. More asphalt was absorbed into the aggregates in W3B-RCA-C37 mixture but lesser asphalt was needed to fill the voids between the more tightly packed aggregates. Incorporation of RCA had resulted in a mixture with denser aggregate structure and a thinner asphalt film, giving higher Marshall stability and better deformation resistance. However, thinner asphalt film and inadequately coated broken aggregates increase susceptibility to moisture-stripping damage to the mixture.