Physical Properties of an Eco-Sustainable, Form-Stable Phase Change Material Included in Aerial-Lime-Based Mortar Intended for Different Climates

Abstract

The aim of this experimental investigation was to produce a form-stable phase change material (PCM) able to reduce the need for nonrenewable energy resources required for the heating/cooling of buildings located in regions characterized by different climatic conditions. The innovative PCM must also be sustainable and must be produced according to the principles of the circular economy. To achieve such ambitious goals, a form-stable, sustainable PCM was produced through vacuum impregnation. The form-stable PCM was produced starting from a low-toxicity, low-flammability polyethylene glycol of medium molecular weight (PEG 800), which was included in porous stone granules obtained as waste products of the cutting/processing of local (Lecce) stone. The thermal properties and thermal stability of PEG 800 and of its PCM-composite were evaluated by employing differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). The appropriate parameters to perform the impregnation procedure were identified through rheological and calorimetric analyses. A simple leakage test was performed to assess if the PEG polymer can leak from the stone flakes. Finally, the new PCM was added as an aggregate in aerial-lime-based mortars, and the mortar’s properties were analyzed in fresh (workability) and hardened (flexural and compressive strength and thermal characteristics) states for potential applications, particularly in ancient buildings.

Physical Properties of Eco-Sustainable Form-Stable Phase Change Materials Included in Mortars Suitable for Buildings Located in Different Continental Regions

“…The greatest reduction in water was observed for the mortar based on cement. This behavior could be attributed to small portions of the PEG800 polymer possessing a low viscosity at room temperature [ 27 ], with portions lying on the surface of the Lecce Stone grains that can contribute to improving the workability of the mortar mix with replacement of a limited amount of the required water. This feature can, nevertheless, represent an important advantage, potentially counteracting the detrimental effects on mechanical properties brought about by the addition of a PCM in the mortars, as previously reported [ 26 , 37 , 38 , 39 ].…”

“…In Figure 6 , the DSC curves of the mortars produced in this study are presented. For comparison purposes, the thermograms relative to the aerial lime mortar, containing the LS/PEG800 composite or not and previously determined [ 27 ], are also reported in Figure 6 a. From the analysis of the DSC curves, the values shown in Table 3 were obtained.…”

“…Starting with the illustrated results, a PEG with a lower molecular weight, i.e., PEG 800, and a melting range of temperatures around 26–32 °C was analyzed in [ 27 ]. The aim was, in fact, the production of a PCM to be added to mortars suitable for cold climates, as in those climates characteristic of countries of Northern Europe.…”

“…Several physical properties of the produced mortars were assessed. In [ 27 ], the characteristics determined on the aerial lime mortar containing LS/PEG800 only were reported. However, for comparison purposes, they are also reported in the present manuscript.…”

“…The purpose of this selection was to evaluate whether a PEG800-based PCM, to be included in different mortars, will act as an effective PCM if applied in buildings located in colder climates. In the first paper [ 27 ], PEG 800 was thermally characterized, alone or when included in the Lecce Stone granules to form the PCM, in order to assess the thermal characteristics and latent heats. In Figure 1 , the calorimetric curves measured by DSC (Differential Scanning Calorimetry) of the PEG-based PCMs produced so far, i.e., LS/PEG800 and LS/PEG1000, are shown.…”