Assessment of high-enthalpy composite eutectic phase change materials efficiency in asphalt binders for cooling pavements

Phase change materials (PCMs) as thermal energy storage solutions can mitigate pavement damage and alleviate the urban heat island effect. A stable shape, suitable melting temperature, and high-enthalpy can extend the application potential of PCMs in cooling pavements. The goal behind this study is to investigate the potential use of two high-enthalpy composite phase change materials (CPCMs) in an SBS-modified asphalt binder through thermal and chemo-rheological tests. Herein, using a ternary eutectic mixture with adipic/sebacic/stearic acids (named A) and a binary eutectic mixture consisting of stearic/palmitic acids (named B) as two distinct PCMs and expanded graphite as supporting material, two novel CPCMs were successfully prepared through vacuum impregnation. The findings showed that the encapsulation efficiency of both CPCM-A and CPCM-B exceeded 90%. The melting enthalpy (Hm) and the melting phase-change temperatures (Tm) values were 193.3 J/g and 61.7 ◦C for CPCM-A, 189.6 J/g, and 50.5 ◦C for CPCM-B. The Hm of the two related asphalt binders that incorporate the developed CPCMs (SBS-A and SBS-B) were 19.5 J/g and 17.2 J/g, respectively, indicating high thermal storage and management capabilities. This allowed SBS-A and SBS-B to exhibit maximum temperature differences of 13.1 ◦C and 10.7 ◦C, with temperature lags of 1500 s and 2610 s, respectively. Also, the CPCMs and the related asphalt binders presented outstanding thermal and chemical stability. The CPCMs enhanced the resistance to deformation and deformation recovery capability of asphalt at high temperatures and under severe loads. However, SBS-B experienced an earlier phase transition than SBS-A, ultimately leading to a diminished ability to withstand deformation at the testing temperature. To sum up, opting for CPCM-A over CPCM-B for asphalt pavement cooling applications is advisable.