Phase change materials are used in cementitious materials to reduce the hydration temperature rise and thus inhibit the temperature cracks generation. However, the influence mechanism of phase change materials on the hydration properties of cementitious materials is still unclear. In this study, ZIF-8-based composite phase change materials (CPCM) were added to the Portland cement (PC) clinker-anhydrite (C$)-calcium sulfoaluminate (CSA) cement ternary system (PCCSA) in the form of admixtures. The effects of controlling the phase change temperatures, dosages of CPCM and hydration temperatures on the hydration exothermic characteristics, hydration products and the compressive strength development in the PCCSA composite system were investigated. CPCM addition reduced the hydration exothermic rate and cumulative heat release of the ternary system, especially when the phase change temperature of CPCM was 25.8 ℃, and the larger the dosage, the more obvious the reduction effect. In addition, CPCM did not participate in the hydration reaction of the system, but promoted the formation of CH and AFm. Simultaneously, the compressive strength of the PCCSA system paste containing CPCM decreased due to increased porosity in the paste. Furthermore, elevated hydration temperature significantly improved the hydration rate of the system, while reduced the hydration degree, and the hydration products types of the system were not affected by the hydration temperatures. This study results are fundamental for predicting the hydration behavior of cement systems containing CPCM and promoting the application of composite phase change materials in cementitious materials.
Li Yan,Wang Shuo,Tan Wangwang,Zhou Shenghui,Zhu Qunzhi
Erythritol (ET) is a promising medium–low temperature organic phase change material. To solve the problems of supercooling, leakage, and low thermal conductivity, expanded graphite (EG) with four different particle sizes of 32 mesh, 50 mesh, 80 mesh, and 100 mesh was used as supporting material. A shape-stabilized composite phase change material (CPCM) with a mass ratio of EG to ET of 9:1 was prepared by the ultrasonic impregnation method. The properties were tested and analyzed by DSC, SEM, FTIR, XRD, and TGA. The experimental results showed that 50 mesh EG was more suitable as an adsorption carrier for erythritol among the four different particle sizes of EG. Compared with pure erythritol, the supercooling degree of 50 mesh EG/ET composite decreased by 35.2 %, the latent heat of solidification increased by 8 %, and the thermal conductivity increased by 250.8 %, which increased the heat storage and release capacity of the material by 19.2 %, and the 50 mesh EG/ET composite phase change material had good thermal stability. In this study, the relationship between the supercooling degree of EG/ET and EG particle size was analyzed, and EG/ET thermal storage materials with high thermal storage density and exothermic density were prepared. It helps to promote the application of EG-based composite thermal storage materials and the development of thermal storage technology.
Dong Zhang,Meizhu Chen,Zongwu Chen,Pengxiang Li,Zhuhai Shao,Xingfei Liu,Pinpin Liu
Polyethylene glycol (PEG) demonstrates significant advantages in asphalt pavement thermal regulation owing to high latent heat and adjustable phase transition temperatures. However, its limitations, including liquid-phase leakage and low thermal conductivity, restrict practical applications. This study developed a functionalized expanded graphite (FEG) matrix via acid oxidation, where oxygen-containing groups establish hydrogen bonds with PEG, forming PEG/FEG CPCM with enhanced thermal conductivity and encapsulation stability. Structural characterization showed FEG interlayer spacing increased from 0.3379 nm to 0.3439 nm, with surface oxygen content rising from 2.66 % to 12.33 % (predominantly −OH/−COOH groups). Hydrogen bonds forming between FEG and PEG restrict molecular chain migration, thereby improving encapsulation stability. The optimized PEG/FEG CPCM exhibited latent heats of 141.60 J/g (melting) and 134.12 J/g (crystallization), a 24.9 % lower supercooling degree (11.39°C vs. 15.17°C), and 11.58-fold higher thermal conductivity (3.6257 W/(m·K) vs. 0.3132 W/(m·K)) compared to pure PEG. Hydrogen bonding increased the decomposition temperature of PEG/FEG CPCM by 10.7°C to 306.4°C, with only a 0.9 % reduction in phase transition temperature and a 1.0 % latent heat loss after 100 thermal cycles. Field tests showed that PEG/FEG-modified asphalt mixtures extended heating/cooling durations by 2.1 %/15.0 %, mitigating pavement thermal distress. The study advances the application of PEG-based CPCMs to enhance pavement durability, mitigate UHI effects, and conserve energy.
危险品化学品经营许可证（带存储）