Design of hot-mix recycled asphalt concrete produced in plant without preheating the reclaimed material

In recent years, in Portugal, some road pavement rehabilitation projects used hot-mix recycled (HMR) asphalt concrete in plant as a technique to perform cost and environmentally effective pavement recycling. One of the main problems raised by the use of HMR is the direct use of mix design procedures developed for conventional asphalt concrete. This paper describes a mix design procedure and a case study carried out for HMR based on the mechanical performance of several blends, which are applicable to common practice in Portugal. The study designed a typical 0/25 bituminous mixture for the base layer, which incorporates up to 40% of reclaimed bituminous material, introduced into the plant mixer without previous heating. Based on the results, it can be stated that the level of confidence is comparable to that obtainable from conventional mixtures, provided that a proper mixture design and some construction directives are used.