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

Abstract

Starting from two low-cost, low-environmental-impact polymers belonging to the Polyethylene Glycol (PEG) family, i.e., PEG 800 and PEG 1000, two form-stable phase change materials were produced. The two PEGs differ in molecular weight and, as a consequence, the melting and crystallization range of temperatures. The PCMs were obtained, including the PEG, in a liquid state, inside the pores of Lecce Stone flakes, obtained as waste pieces from its processing. A simple and inexpensive impregnation process was selected to produce the PCMs, thus adopting low-environmental-impact materials and cheap processes, and respecting circular economy principles. The two PCMs, the first composed of PEG 800, namely LS/PEG800, and the second composed of a 50/50%wt. mix of the different LS/PEGs, i.e., LS/PEG800_LS/PEG1000, were added as aggregates to four types of mortars, based on aerial and hydraulic lime, gypsum, and cement. The obtained mortars were characterized in their fresh state to assess their workability, and in a solid state after a proper cure to determine their characteristic Latent Heat Thermal Energy Storage (LHTES) properties and mechanical properties in both flexural and compressive modes, taking the mortars not containing any PCM as the reference. The results revealed that, with the proper selection of mortar formulations, it was possible to achieve suitable workability and adequate mechanical characteristics. The selection of a PEG with a low range of phase change temperatures, such as PEG 800, allows one to obtain mortars characterized by a melting/crystallization range that can be considered appropriate in applications characterized by cold climates. The production of a mixed PCM, composed of both PEGs, led to mortars displaying a large interval of melting/crystallization temperatures, which could be suitable in both warm and cold climates.

Selection of PEG-Matrix Combinations to Achieve High Performance Form-Stable Phase Change Materials for Building Applications

“…In another study [30], the development of a form-stable PCM based on PEG1000 embedded into flakes of waste Lecce stone (LS), byproducts of the processing of this very porous stone, was investigated for possible applications in different mortars. Further investigations, reported in [107][108][109][110], analyzed different compositions of PEG800-based and PEG1000-based PCMs within LS, in order to identify the PCM composition giving rise to the best performance when included in mortars based on different binders (aerial and hydraulic limes, gypsum, and cement). In [111][112][113], the thermal performance of PEG800/LS and PEG1000/LS PCMs was assessed, taking as reference two different climate zones (i.e., Mediterranean and continental Europe); the produced PCMs proved to be particularly effective in reducing temperature fluctuations in hot seasons.…”

Green Thermal Aggregates: Influence of the Physical Properties of Recycled Aggregates with Phase Change Materials

“…There are four methods for applying PCM to building materials, such as direct incorporation [ 16 , 17 ], encapsulation [ 18 , 19 , 20 ], immersion [ 21 , 22 ], and form-stable methods [ 22 , 23 , 24 ]. Many researchers have presented studies in which they utilize PCM in construction products [ 24 , 25 , 26 ], namely, interior coating mortars, with the aim of increasing the thermal comfort of building occupants [ 27 , 28 , 29 , 30 , 31 ]. Cunha et al [ 32 ] directly mixed pure paraffin into mortar to improve the thermal performance of the mortar and reduced the indoor temperature difference by about 3 °C in summer.…”

“…The “form-stable composite PCM” method [ 23 , 24 ] consists of absorbing PCM in aggregates or frames with a certain porosity and then using them in building materials. For this method, the final thermal properties of the materials are determined by the amount of PCM absorbed by the aggregate, while the porosity/water absorption of the aggregate determines the amount of PCM that it absorbs.…”

“…There are four methods for applying PCM to building materials, such as direct incorporation [16,17], encapsulation [18][19][20], immersion [21,22], and form-stable methods [22][23][24]. Many researchers have presented studies in which they utilize PCM in construction products [24][25][26], namely, interior coating mortars, with the aim of increasing the thermal comfort of building occupants [27][28][29][30][31].…”

Use of sustainable Phase Change Material (PCM) in mortars for building energy efficiency

“…Lecce stone, was selected as inert matrix for the PCMs. The preparation of these materials and their characterization (chemical, physical, thermal and morphological) was deeply studied and reported elsewhere [20][21][22][23]. Following these studies, it was possible to state that the PCM composite material is appropriate for the intended purpose: thus, it can be used as an aggregate for mortars.…”