Short-term performance appraisal of half-warm mix asphalt mixtures containing high (70%) and total RAP contents (100%): From laboratory mix design to its full-scale implementation

Abstract

Asphalt mixtures requiring lower mixing, spreading and compacting temperatures have received considerable worldwide attention in the recent years as a way to reduce energy consumption and pollutant emissions. However, many questions are still unanswered regarding the field performance of those mixtures under loading and environmental conditions. In this study, half-warm mix reclaimed asphalt (HWMRA) mixtures containing high (70%) and total reclaimed asphalt pavement (RAP) contents (100%) for use in wearing and binder courses of urban areas were evaluated both in laboratory and in field. HWMRA mixtures with 70 and 100% RAP content were designed in laboratory from a preliminary field investigation aimed at characterizing the existing materials in an urban pavement. Posteriorly, the mixtures were manufactured in a prototype asphalt plant at a mixing temperature below 100 °C and with bitumen emulsion. Furthermore, an urban test section was built to compare its mechanical performance with that of a contiguous section comprising conventional hot mix asphalt (HMA) mixture. In addition, core samples were extracted from the evaluated sections after construction and one year later, and tested in laboratory to determine thicknesses, density, stiffness modulus, indirect tensile strength (ITS) and fatigue resistance at 20 °C. Surface friction characteristics (i.e., skid resistance and macrotexture) were also assessed and compared with those of the HMA pavement section. The results of the laboratory tests conducted on core samples showed that the performance of the HWMRA mixtures can be compared to that of HMA mixtures in terms of fatigue resistance and resistance to permanent deformations. These findings encourage greater confidence in promoting the use of these types of sustainable asphalt mixes.