Early age temperature control in mass concrete through incorporation of dispersed Phase Change Materials (PCMs)

Abstract

There is a frequent need to take measures for temperature control in massive concrete structures, as to avoid thermal cracking risk at early ages (induced by temperature gradients inherent to hydration heat release). This research work has explored a procedure for temperature control through the incorporation of phase change materials (PCMs) in laboratory environment (mortar testing). Indeed, PCM?s have the potential to store and release heat energy during phase change from solid to liquid, or vice versa. By choosing a PCM with a melting range between casting temperature and the expected peak temperature, it is possible to attenuate the temperature rise rate in concrete through heat storage (the melting process is endothermic). This paper presents and discusses an experimental work focused on the thermo-physical properties and thermal performance analysis of mortar with direct incorporation of pristine PCM (with a melting temperature of 34ºC and latent heat capacity of 240 J/g) in three volume fractions of 0, 10 and 20% in mixture compositions (volumetric percentage replacement with regard to sand particles), cast into partially insulated cubes with 320mm3 size. The thermal performance tests revealed the impact of the PCM in the thermal behavior of the cast element, by reducing the maximum peak temperatures in comparison with the reference case (without PCM). Mechanical tests were also performed and revealed that, as expected, their compressive and flexural strength are reduced. Nonetheless, the observed reduction might still be compatible with structural applications in specific contexts, even for the case of high PCM content incorporation (20%).