Investigation of the effectiveness of microencapsulated phase change materials for bitumen rheology

Abstract

Summary The rheological properties of asphalt pavement have temperature susceptibility. Bitumen is binding material and affects directly the properties of the asphalt mixture. Asphalt pavements become hard and brittle as bitumen is more sensitive to cracking in cold regions. Phase change materials (PCMs) can be used to prevent or delay freezing asphalt pavements at low temperatures. For that reason, raw n‐tetradecane possessing a melting point of around 6°C was preferred as an organic PCM in this study and bitumen 10/20 and 50/70 were modified with n‐tetradecane. It was observed that PCM extremely rose the penetration grade of bitumen and decreased softening point due to the leakage of PCM. Three new microencapsulated phase change materials (MPCMs) were synthesized with different shell materials through emulsion polymerization technique to prevent the leakage of the PCM. Poly(methyl methacrylate) (PMMA) based MPCMs (MPCM‐1 and MPCM‐2) and polystyrene (PS) based MPCM (MPCM‐3) were prepared with a crosslinker monomer, ethylene glycol dimethacrylate (EGDM). In addition, 2‐hydroxyethyl acrylate (2‐HEA) and 2‐hydroxyethyl methacrylate (2‐HEMA), were used as comonomer in the fabrication of MPCM‐1 and MPCM‐2, respectively. The latent heat storage capacities of MPCM‐1, MPCM‐2, and MPCM‐3 were calculated as 53.3, 52.2, and 116.9 J/g, respectively. The results of the differential scanning calorimeter (DSC) analyses revealed that PS based MPCM had higher latent heat than PMMA based MPCMs. Scanning electron microscope (SEM) and particle size distribution (PSD) analyses indicated that the MPCMs had nearly spherical geometry and particles distributed around the mean particle size unimodally. Thermogravimetric analysis (TGA) exhibited that MPCMs degraded at considerably high temperatures as compared to the possible ambient ensuring high thermal durability. The current study also aims at evaluating the rheological properties of bitumen modified with PCMs and MPCMs. For this reason, softening point and penetration grade of bitumen modified with PCM and MPCM were studied. Softening point and penetration grade analyses showed that microcapsules considerably prevent leakage of PCM. Dynamic Shear Rheometer (DSR) analyses were also investigated to evaluate physical properties of bitumen modified with PCM and MPCM. DSR analyses revealed that the addition of MPCMs into bitumen preserved elastic structure and prevented softening of the bitumen as compared to the addition of PCM.

Advancements in Phase Change Materials in Asphalt Pavements for Mitigation of Urban Heat Island Effect: Bibliometric Analysis and Systematic Review

“…For instance, SiO 2 encapsulation is frequently used with popular PCM like PEG2000 and PEG4000 [ 25 , 38 , 41 , 42 ]. Additionally, there are less commonly used strategies, such as adsorption on diatomite silica microporous structures [ 62 , 64 ], the use of PCM in composite form [ 38 , 58 ], polymerisation [ 31 , 77 , 78 ], emulsion polymerisation [ 52 ], and integration with multi-walled carbon nanotubes (MWCNT) [ 45 ], along with more advanced techniques like microencapsulation [ 79 ] and shape-stabilised expanded graphite [ 26 , 80 ]. Carrier matrix materials can also influence the thermal properties of PCM under various conditions (as shown in Table A1 ).…”

“…Integrating PCM into asphalt mixtures, a significant development in materials science, must consider various aspects, including potential impacts on mechanical properties and the degree of thermal improvement realised [ 25 , 36 , 37 , 38 , 77 ]. The data in Table A3 reveal that these materials effectively manage thermal energy absorption and release, thus regulating temperature fluctuations in asphalt pavements [ 52 , 78 , 96 , 97 ].…”

“… Wet mixing 5%, 10%, 15%, and 20% ( w / w ) [ 70 ] n-Tetradecane Emulsion polymerization. Wet mixing 1%, 3%, 5%, and 10% ( w / w ) [ 52 ] n-Alkane C 2 0H 42 (Eicosane) Microencapsulated eicosane in asphalt concrete. Dry mixing Different volume fractions of PCM (up to 15 vol%) [ 79 ] Silica with ethyl cellulose (EC) Pavement capsules.…”

“…Excessive content of encapsulated PCM (>3%) negatively affected rheological properties. [ 52 ] n-Alkane C 2 0H 42 (eicosane) Reduction in surface temperature by 2.7 °C. The profile of the complex shear modulus in AC pavement could be optimized by choosing the adequate thermal behaviour of AC pavement.…”

“…In Table A1, certain PCM, such as small-molecule alkane [36], n-tetradecane [31,52], PEG 800 mixed with polyacrylamide [53,54], solid-solid PCM (provided by a commercial company) [55], silica with ethyl cellulose [56], ethyl cellulose [57], four different types of composite phase change materials (CPCM) [58], and tetradecane (n-alkane C14H30) [59], have melting points around 20 • C or lower, which could make them not particularly effective in asphalt temperature regulation to mitigate the UHI effect. A PCM with a melting point around 20 • C would not be suitable for applications in which the temperature can reach 60 • C. This is because the PCM would melt at 20 • C, and then it would not be able to store any more heat [60].…”