Mechanical properties and Freeze-Thaw durability of concrete modified with microencapsulated phase change materials

Microencapsulated phase change materials (mPCM) emerge as sustainable thermal energy regulation additives for enhancing concrete durability in cold climates. This investigation systematically evaluates the dose-dependent effects of mPCM incorporation (0-12% cement replacement) on mechanical-strength development and freeze-thaw resistance through comprehensive mechanical testing, 100-cycle accelerated freeze-thaw evaluations, and quantitative microstructural analysis. The experimental findings reveal a critical biphasic relationship: Optimal 6% mPCM addition significantly enhances mechanical performance with 8.90%, 19.23%, and 30.72% improvements in ompressive strength, flexural strength, and splitting tensile strength versus control, while maintaining exceptional frost durability (1.6% mass loss and < 15% strength degradation post-freeze-thaw). Microstructural analysis reveals that 6% mPCM optimizes the pore structure of concrete by reducing pore size and moderately increasing porosity, thereby enhancing freeze-thaw durability. Beyond the critical 9% threshold, the concrete matrix becomes loose, leading to a decline in overall strength. The established dosage-property correlation provides practical guidance for cold-region concrete design, demonstrating that 6% mPCM incorporation achieves synergistic enhancement of load-bearing capacity and phase-change-enabled thermal stress mitigation.