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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reasonable given that, as per the recipe, MPCM replaces part of the binder. For foamed concrete with a density of 350 kg/m 3 , the strength was relatively low, measuring 1.35 MPa without MPCM. The addition of 10% and 20% MPCM relative to the paste volume decreased compressive strength by 17% and 30%, respectively. In contrast, for foamed concrete of higher densities - 500 kg/m 3 and 700 kg/m 3 - the decrease in strength due to MPCM presence was less pronounced, amounting to 16% and 10% for 10% MPCM, and 24% and 22% for 20% MPCM, respectively for density of 500 kg/m 3 and density of 700 kg/m 3 . Furthermore, the obtained compressive strength results were compared with autoclaved aerated concrete ( AAC) manufacturer data. According to the Polish company (Solbet, 2024), AAC with a density of 350 kg/m 3 exhibits a strength of 1.7 MPa, making the compressive strength of the tested foamed concrete with this density 20% lower. At a density of 500 kg/m 3 , the strength of foamed concrete is only 6% lower than AAC (with a manufacturer-stated strength of 2.5 MPa), and at a density of 700 kg/m 3 , it even surpasses AAC strength by 10% (manufacturer-stated strength of 4 MPa). Nevertheless, it appears that further modifications to the foamed concrete composition are necessary to enhance its strength, such as incorporating micro-silica fume.

Fig. 4. Compressive strength of the tested samples

The heat conductivity test results presented in Fig. 5 clearly demonstrate the positive impact of incorporating MPCM into foamed concrete. Thermal conductivity decreases notably, enhancing foamed concrete's thermal insulation properties. Similar to strength, the influence of MPCM varies with its amount and is also influenced by the foamed concrete density. For the lowest density of 350 kg/m 3 , adding 10% MPCM reduces the thermal conductivity by 10%, while 20% MPCM reduces it by 18%. At densities of 500 kg/m 3 and 700 kg/m 3 , the decrease in the thermal conductivity coefficient after MPCM addition is more substantial, ranging from 12% (500 kg/m 3 with 10% MPCM) to 27% (700 kg/m 3 with 20% MPCM). Comparing these findings with AAC data from Solbet, the manufacturer provides thermal conductivity coefficient values of 0.08 W/(mK), 0.135 W/(mK), and 0.19 W/(mK) for the tested densities of 350 kg/m 3 , 500 kg/m 3 and 700 kg/m 3 . These values are lower than those obtained for the tested foamed concrete without MPCM, where densities yielded 0.105 W/(mK), 0.15 W/(mK), and 0.202 W/(mK), respectively. However, the introduction of MPCM significantly enhances this property, resulting in either similar (at 350 kg/m3 density) or even lower thermal conductivity (at 500 kg/m 3 and 700 kg/m 3 densities) compared to AAC. The specific heat test results are provided for a single tested density, specifically 500 kg/m 3 ( Fig. 6 ) As expected, there is no visible peak in specific heat since the foamed concrete does not contain MPCM, and specific heat values only exhibit slight variations from 0.94 kJ/(kgK) to 1.02 kJ/(kgK) across the investigated temperature range. The average specific heat value for the sample without MPCM is 0.95 kJ/(kgK). The melting point for the utilized MPCM is 24°C ±2°C, with a heat of fusion of 184 J/g. Upon adding 10% or 20% MPCM to the foamed concrete, the specific heat capacity results display a peak within the MPCM's melting range. Starting at lower temperatures, the specific heat values are approximately 1.15 kJ/(kgK) and 1.26 kJ/(kgK) for 10% and 20% MPCM content, respectively - significantly higher than the values obtained for foamed concrete without MPCM (representing a 21% and 32% increase, respectively). Subsequently, there are substantial increases in specific heat starting around 18°C, reaching maxima of 2.4 kJ/(kgK) for 10% MPCM and 2.8 kJ/(kgK) for 20% MPCM at 24°C. These values then decrease