Hydration heat and hydration products evolution of PC clinker-C$-CSA cement ternary system containing ZIF-8-based composite phase change materials

Abstract

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.