Influence of recycled concrete and steel slag aggregates on warm-mix asphalt properties

Abstract This paper focuses on the comparison of the mechanical performance of three warm-mix asphalt (WMA) blends with recycled concrete aggregate (RCA) or electric arc furnace slag (EAFS) as substitutes of part of the aggregate. A conventional hot mix asphalt (HMA) and a WMA without by-products were used as references. The evaluation was carried out in a laboratory by means of testing specimens taken from experimental pavement sections built in real production, laying and compaction circumstances. Performance testing included wheel-tracking tests, four-point bending tests, and indirect tensile strength to assess water sensitivity. An organic wax and a chemical surfactant were applied to lower handling temperatures of the WMA under study. Apart from the HMA and the WMA used as references, the study evaluated the influence of introducing 60% of RCA or 30% of EAFS into the WMA blends as substitutes of the aggregate. The obtained results for the WMA with by-products tested allowed to conclude that the introduction of EAFS or RCA into the WMA blends increases Marshall stability and may increase or decrease resistance to rutting. Findings also showed that stiffness modulus is somewhat reduced and fatigue resistance does not change significantly. Additionally, water sensitivity is slightly reduced. Comparing these results with the performance observed elsewhere for WMA without by-products revealed that the addition of RCA or EAFS is satisfactory. The construction of experimental sections used conventional batch plant, paver and compactors without any noticeable technical problems.