Thermo-regulation, mechanical performance and microstructural characteristics of alkali-activated slag mortars produced with magnetized water

This study investigated the combined effects of magnetized water (MW) and microencapsulated phase change materials (mPCM) on the physical, mechanical, thermal, and microstructural properties of alkali-activated slag (AAS) mortars. In the first stage, isolated mPCM was characterized by PSD, DSC, FT-IR, POM, and SEM analyses and was found to largely maintain its thermal stability after 1000 heating–cooling cycles. In the second stage, the optimum activator molarity was determined to be 8 M in AAS mortars produced using NaOH molarities of 6, 8, 10, and 12 M. In the final stage, AAS mortars containing 5%, 7.5%, and 10% mPCM were produced using TW and MW. The results showed that increasing mPCM content significantly improved thermoregulation performance while decreasing workability and mechanical properties. The use of MW increased workability, compressive strength, flexural strength, and UPV values by 15.4%, 39.3%, 33.6%, and 28.2%, respectively. Thermal analyses revealed that mPCM addition reduced temperature fluctuations, creating a temperature difference of up to 2.8 °C in samples containing 10% mPCM compared to the reference mixture. Furthermore, mPCM-containing AAS mortars largely retained their thermoregulation performance after 50 heating–cooling cycles, indicating stable cyclic thermal behavior under the investigated conditions. SEM, XRD, FT-IR, and MIP analyses indicated a more compact matrix and a more refined pore structure in MW-containing mortars. In conclusion, MW partially compensated for the mechanical performance losses caused by mPCM while preserving its thermoregulation benefits; however, the observed effects are specific to the GBFS and mPCM system investigated in this study and require validation with other GBFS sources and mPCM types.