Investigate the Impact of Microencapsulated Phase Change Materials in Microsurfacing

Abstract: Microencapsulated Phase Change Materials (MPCMs) can induce temperature control properties in asphalt materials. Thus, the use of MPCMs in asphalt pavement has the potential to mitigate urban heat island effects, freezing temperatures, rutting, and cracking distress, depending on their melting points. However, their practical application in hot mix asphalt is limited due to the potential breakage of the outer shell of MPCMs particles under high temperatures in asphalt plant conditions. Therefore, an alternative approach of incorporating MPCMs into asphalt pavement systems is necessary which can enhance their practical applications. Over the years, microsurfacing has emerged as an effective, economical, and environmentally friendly pavement preservation treatment. Microsurfacing is cold slurry asphalt mixtures that involves mixing polymer-modified asphalt emulsion, aggregates, filler, cement, and water at ambient temperatures. Use of MPCMs in microsurfacing could ensure the encapsulation integrity of MPCMs particles and their respective performance, as the microsurfacing mixing process does not involve high temperatures. However, this research approach of using MPCMs as an additive in microsurfacing has not been studied yet. Thus, the goal of this research is to modify microsurfacing using MPCMs and study their performance and encapsulation integrity. A Type II Microsurfacing gradation with 100% RAP material and a cationic quick setting polymer modified asphalt emulsion (CQS1-hP) were utilized in the study to prepare microsurfacing mixes. The modified microsurfacing mixes were produced using two types of MPCMs with melting points of 6°C and 28°C, respectively, and dosages of 1% and 2% by weight of aggregates. The encapsulation integrity of MPCMs in microsurfacing was studied using a differential scanning calorimeter and a temperature control test in a universal testing machine chamber. The prepared mixes were then tested for their mix time, wet cohesion, wet track abrasion loss, lateral displacement, and sand adhesion properties. The results indicated that the enthalpy of modified microsurfacing increased with the increase in the dosage of both types of MPCMs. Moreover, the expected enthalpy for each type and dosage of MPCMs was close to the measured enthalpy, indicating that the encapsulation integrity of the MPCMs was not compromised during the mixing process. The temperature control test revealed that at the respective melting points of MPCMs, the temperature difference ranged between 4–8ºC. The mix time test showed that all mixes met the minimum requirement of 120 seconds according to ISSA specifications. The wet cohesion test also revealed that at 30 minutes and 60 minutes, all mixes passed the required thresholds of 12 kg-cm and 20 kg-cm, respectively. The performance tests indicated that abrasion loss decreased with the addition of MPCMs in microsurfacing. However, there was a decrease in the rut depth and sand adhesion characteristics. Thus, it can be concluded that the addition of MPCMs to microsurfacing results in a better-performing microsurfacing mixture, with the added benefit of improved resistance to rapid environmental temperature changes.