Mechanism of Water-Resistant Performance Enhancement in Paraffin Phase-Change Film–Forming Cement-Based Materials

Abstract

The effects of the baking temperature and paraffin content on the water resistance and degree of phase change of paraffin phase-change film–forming cement-based materials (PPFCMs) were studied by observing the phase-change melting state of paraffin in cement-based materials mixed with paraffin powder under the action of baking and measuring the water absorption and degree of seepage of specimens immersed in water for an extended period. The hydrophobic characteristics of the cement matrix and microscopic morphology of its internal phase-change paraffin film were studied. The results indicated that the water absorption of the PPFCM immersed in water for a long time (30 days) decreased significantly at first and then decreased gently with the increase in the paraffin content and baking temperature. The specimens could achieve the effect of blocking water infiltration with a decrease in the water absorption to a stable value. When the baking temperature was high (>80°C), the paraffin inside the cement-based material could be melted into the best colorless and transparent adhesion state. The phase-change paraffin in the cement matrix exhibited a relatively dense, smooth, and film-like structure at the microlevel. These films firmly adhered to the surface of the cement stone structure, endowing the PPFCM with excellent hydrophobic properties (water contact angle >90°). This study highlights the significant benefits of using paraffin as a phase-change material to create a hydrophobic sealing film in cement-based materials, particularly for applications where water resistance is crucial. By subjecting the hardened cement matrix with added paraffin powder to baking treatment, construction materials can be engineered to achieve superior water-resistant performance, effectively blocking water infiltration. The findings indicate that the cement matrix with a paraffin content of at least 3% and a baking temperature of 80°C or higher demonstrates excellent water repellency, making it ideal for use in environments exposed to moisture or corrosive substances. This study provides helpful insights for engineers and builders seeking to improve the longevity and reliability of cement-based products under challenging conditions. Additionally, the findings align with the increasing emphasis on sustainable construction practices, as utilizing phase-change paraffin to create a long-term effective hydrophobic sealing film may reduce the necessity for supplementary waterproofing chemicals and coatings, thereby minimizing the environmental impact.