Beautoklavio putbetonio šiluminių techninių savybių tyrimai/Investigation into non-autoclaved foam concrete heat engineering properties

Abstract

The purpose of this investigation was to determine various density foam concrete heat engineering properties. These properties are not included in valid construction standards [1]. Thermal conductivity of samples was determined at 25°C according to [2], specific heat—[3], vapour permeability—[4] and sorption moisture—[5]. Dry foam concrete thermal conductivity (W/m-K) dependency on its density is given in Fig. 1 as well as after mathematical statistical treatment using the regressive equation [1]. Foam concrete thermal conductivity dependency on its humidity statistical analysis results is given in Table 1, here ΔλW s and ΔλW t is the average absolute thermal conductivity increase for 1% materials moisture according to mass and volume, while and δW s δW t is the same increase, but in percentage value. Foam concrete thermal conductivity dependency on moisture is linear. The specific heat value for 245 and 840 kg/m3 density foam concrete is 980±50 and 850±50 J/kg·K respectively. The determined foam concrete sorption moisture is given in Fig. 2 and Table 2. The steep moisture increase at high ambient air humidity is defined by adsorption and the beginning of capillary condensation. This state is not noted in literature curve 2 [7] and evidently due to the short experimental interval. The vapour permeability results for foam concrete are given in Fig. 3 and using the regressive equation (2). Our results are approximately 13% lower than those given for porous concrete [1]. The calculated thermal conductivity was determined using equation (3), assuming that the sorbtion moisture is equal to the relative air humidity (80–85)% (Table 2). Then 250, 500 and 800 kg/m3 density foam concrete λ(ρ0, Wsk) is equal to 0,12, 0,19 and 0,32 W/m·K respectively. The foam concrete heat capacity coefficients S, calculated according to formula (4) for temperature fluctuation period z=24 h and according to damp foam concrete density and specific heat are given in Table 3. Experimental for 260, 500 and 800 kg/m3 density non-autoclaved foam concrete heat engineering values are given in Table 4. For comparison, the denominators (under the line) show the corresponding values for porous concrete given in [1], It is purposive to use in practical calculation specific non-autoclaved foam concrete heat engineering values because these differences are substantial. First Published Online: 26 Jul 2012

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