Improving freeze resistance of cement-based materials with modified graphite-paraffin composite low-temperature microencapsulated phase change materials

Abstract

This study examines the influence of microencapsulated phase change materials (MPCM) on enhancing the freeze-thaw resistance of cementitious structures, overcoming the limitations commonly associated with traditional phase change materials (PCM), such as insufficient thermal conductivity and non-optimal phase change temperatures. The research focused on developing MPCM with improved thermal conductivity and lower phase transition points, utilizing a binary mixture of tetradecane and hexadecane as the core material, supplemented by modified graphite. The phase change performance and physicochemical stability of the prepared MPCM were thoroughly assessed. Cement specimens, incorporating different contents of MPCM, were then subjected to a series of tests under both room temperature and simulated freeze-thaw conditions. These tests included mechanical testing, temperature response experiments, and monitoring of internal damage. The findings identified the optimal MPCM formulation as a 9:1 mixture of tetradecane and hexadecane, with an addition of 2 % hydrophobically modified graphite, which exhibited a phase change temperature near 0 °C and a range exceeding 6.7 °C, along with stable physicochemical properties. When 3 % MPCM was included in cement specimens cured for 28 days under freeze-thaw conditions, a significant reduction in internal damage caused by freeze-thaw cycles was observed, leading to an increase in compressive strength by 0.12 % and in flexural strength by 11.77 %. Additionally, temperature tests confirmed the efficacy of MPCM in stabilizing internal temperature fluctuations within the cement specimens. The results of this study present a viable approach to enhance the durability of cement-based infrastructure in cold climates.