PSI - Issue 64

Barbara Klemczak et al. / Procedia Structural Integrity 64 (2024) 1126–1133 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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concrete. Despite the current limited scope of results, this innovative approach aligns with broader efforts to develop sustainable building materials that offer lower environmental impacts and advanced functionalities, warranting further exploration. In detail, the article presents the results of tests on foamed concrete enriched with Microencapsulated Phase Change Materials (MPCMs) in the amount of 10% and 20% of the paste volume. The densities of the tested FC were selected concerning typical AAC products, i.e., 350 kg/m 3 , 500 kg/m 3 and 700 kg/m 3 . The basic thermal and mechanical properties were examined. Therefore, this study aimed to assess the properties of foamed concrete (FC), particularly when incorporating Microencapsulated Phase Change Materials (MPCM), as an alternative to AAC. The research used some results of the NRG-STORAGE project (NRG – STORAGE Integrated Porous Cementitious Nanocomposites In Non-Residential Building Envelopes For Green Active/Passive Energy Storage, 2024.). 2. Materials and methods The tested foamed concrete (FC) recipes were developed based on findings from the NRG-STORAGE project (Klemczak et al., 2024) . All specimens were prepared using the pre-forming method. Initially, a paste was created in which white Portland cement CEM I 52.5R (OPC) and metakaolin (MK) served as binders. The water-to-binder ratio for all mixes was maintained at 0.4. To ensure the stability of FC, three additives were incorporated into the paste. A polycarboxylate ether-based superplasticizer (SP) provided the necessary workability, while an organic-component based stabilizer (ST) ensured the homogeneity and stability of the composite. Additionally, a hardening accelerator (HA) containing calcium nitrate was used to speed up curing, stabilise pore structure, and ensure proper pore size. Further, a protein-based foam with a density of 70 kg/m 3 was incrementally added to the paste and thoroughly mixed until a uniform blend was achieved. The foam was generated using the Gertec foam generator, a compact device designed for foam production (Gołaszewski et al., 2022) . Control parameters for foam production included water flow, compressed air flow, and foaming agent concentration. In the tests, foam with a density of 70 kg/m 3 was generated using 40 dm 3 /min of compressed air and 3 dm 3 /min of water. Microencapsulated Phase Change Material (MPCM), comprising 10% or 20% of the paste volume, was introduced into the paste. Commercial Paraffin-based MPCMs with a melting/solidification temperature of 24°C were utilised in this study. Key properties of the applied MPCMs (Nextek 24D), produced by Microtek Laboratories (Microtek Laboratories, inc., 2024.) , are detailed in Fig.1 and Table 1 . Foamed concretes without MPCMs were also examined. The densities of the tested foamed concretes were selected to match typical AAC products: 350 kg/m 3 , 500 kg/m 3 , and 700 kg/m 3 . The details of recipes used for all tested foamed concretes are listed in Table 2 . Generally, the study investigated the impact of density and MPCM content on the basic mechanical and thermal properties of foamed concrete (FC), aiming to compare it with properties of Autoclaved Aerated Concrete (AAC) with the same densities. To assess these impacts on compressive strength, testing followed the guidelines of EN 196 1:2016-07 (used for cement mortars) using half of the prismatic specimen measuring 40 mm × 40 mm × 160 mm (see exemplary samples in Fig. 2 a ). The tests were conducted after 28 days of FC curing, with the reported results representing averages from 6 samples.

Fig.1. DSC tests of the applied MPCMs (Nextek 24D)