Characterization of Half-Warm–Mix Asphalt with High Rates of Reclaimed Asphalt Pavement

The current growing awareness about the preservation of the environment, has led the asphalt technicians to assess and correct resulting impacts from the manufacture and application of bituminous mixtures. The concept of sustainability has come to the field of bituminous mixtures with two main components: reducing emissions and consumption of raw materials and preserving resources for the future. Conservation and rehabilitation activities of road pavements generate an increasing amount of waste from the milling of the layers of damaged asphalt mixtures. This material, which has great costs and exceptional properties, should be reused in manufacturing new mixtures of the same type and function. This paper presents the efforts carried out to develop a technology that allows manufacturing and applying half-warm mix asphalt in surface layers of low speed roads at low temperatures using high percentages of reclaimed asphalt pavement (RAP). Continuously graded mixtures were manufactured at 100oC and compacted at 80oC with different percentages of RAP, ranging from 50% to 100%. The results obtained from testing laboratory specimens indicated that their mechanical properties, regarding cracking resistance and fatigue resistance, were very close to those expected from regular Hot Mix Asphalt mixtures. In addition, a field study was carried out in which this technology was put to use. First field cores were extracted and tested from the old pavement and then the RAP coming from this pavement was employed to manufacture laboratory specimens with different gradation, RAP and emulsion contents. The results showed that the use of this technology provided the new mixture with improved fracture properties and ductility with respect to the old pavement mixture. The work presented in this document is part of the Sustainable Urban Surface Asphalt Layers research project (IPT-2012-0316-370000), funded by the Spanish Ministry of Economy and Competitiveness.