The mechanical properties of asphalt mixtures with Recycled Concrete Aggregates

The need for sustainable asphalt highway design and construction is becoming a priority within the asphalt transportation industry. This trend is necessitated by the high diminishing rate of construction materials, pressing demand on existing landfill sites, rising dumping fees, and reduced emissions into the environment. Recycled Concrete Aggregates (RCA) as sustainable aggregates in Hot Mix Asphalt (HMA) is therefore investigated in this research project. The objective of this study is to characterize the mechanical properties of asphalt mixtures with recycled concrete aggregates for low volume roads (herein, the equivalent standard axle load number is low). In this study, the RCA is substituted for Michigan traprock virgin aggregates (VA) in a light traffic volume HMA (control mix) at the rate of 25, 35, 50 and 75. The hybrid VA-RCA HMA is then assessed using the Superpave™ mix performance specifications. The rutting potential using Asphalt Pavement Analyzer (APA), Dynamic Modulus (E∗), Tensile Strength Ratio (TSR) for moisture susceptibility, Indirect Tensile Test (IDT) resilient modulus and the Construction Energy Index (CEI) are determined to evaluate the field performance suitability or otherwise of the mix. All 4 hybrid VA-RCA HMA mixes passed the minimum rutting specification of 8 mm. The master curves for the hybrid mixes showed that the dynamic stiffness of the hybrid mixes were less than that of the control 4E1 mix, and it decreased when the RCA increased in the mix. In terms of moisture susceptibility, the tensile strength ratio increased with decreasing RCA; with only the 75% of RCA in the mix failing to meet the specification criterion. The compaction energy index proved that using RCA would save some amount of compaction energy. It is recommended that a certain amount of RCA in HMA is acceptable for low volume roads.