Critical factors for the selection of phase change materials for asphalt mixtures: a systematic review

Abstract

Phase change materials (PCMs) have emerged as a solution to control the in-service temperature of asphalt pavement, minimizing pavement distress and mitigating the effects of the Urban Heat Island (U.H.I.). This review article provides a comprehensive analysis of the critical factors for selecting, incorporating and evaluating a PCM for asphalt mixtures. It explores the types of existing PCMs (organic, inorganic and eutectic) and the methodologies of incorporation into the asphalt mixture according to the PCM format (direct incorporation, carrier materials or encapsulation) and the moment in which it is combined in the asphalt mixture (wet or dry process). It also emphasizes the importance of performing thermal and mechanical tests to verify the properties of the PCM and the impact on the asphalt mixture, together with the conditions under which the PCM is exposed during manufacture, compaction and commissioning of asphalt mixture for a correct selection of the PCM. The results of this review reflect that the most investigated PCM for an asphalt mixture is polyethylene glycol (PEG) and the format of use of PEG has been two carrier materials, SiO2 and Polyacrylamide, while the most used combination in asphalt mixture is the addition of PCM to bitumen before mixing with aggregates. Finally, this review shows that the temperature reduction ranges from 1.5 °C to 10.5 °C and it is noteworthy there is no single solution on the use of a PCM in the asphalt mixture, since it depends on the purpose and the effect to be generated in the pavement.