Thermal behavior of cement mortar embedded with low-phase transition temperature PCM

Abstract

This study examines the thermal behavior of cement mortar incorporating low-phase transition temperature phase change materials (PCM) (around the freezing point of concrete pore solutions) in an attempt to develop a novel strategy to reduce the expected number of freeze-thaw cycles concrete experiences and possibly to improve the frost resistance. To determine a viable inclusion method for PCM, thermal responses of mortars with two different PCM inclusion methods were tested under a 24-h sinusoidal temperature history, with the maximum and minimum ambient temperatures of 9 °C and −5°C, respectively, considering typical winter climate conditions in South Korea: (1) direct inclusion of non-treated raw PCM; and (2) inclusion of PCM-filled highly absorptive lightweight aggregates (LWA). In addition, another series of testing was conducted to identify the effect of phase transition temperature distribution on the thermal response of cement mortar: (1) inclusion of multi PCMs with three different transition temperatures (4.5 °C, 2.0–2.5 °C, and −0.5 °C); and (2) inclusion of single PCM with a phase transition temperature of 4.5 °C. Lastly, to see the effect of partial PCM embedment, thermal responses of cement mortars overlaid with three different PCM-embedment depths (20 mm, 30 mm, and 40 mm) were evaluated. Results have shown that the minimum specimen temperature was successfully raised by the addition of low-phase transition temperature PCMs. Also, it was revealed that the use of multi PCMs-filled LWA performed most effectively in terms of thermal and mechanical properties as compared to other incorporation methods. The partial PCM embedment improved the thermal performance, but there was no significant effect of PCM embedment depth. © 2020 Elsevier Ltd