Thermal Analysis of Lightweight Clay Bricks with Typha-Fiber Additives

Abstract

This paper assesses the thermal performance of reinforced Typha-fibers unfired clay bricks. Various Typha additive proportions (0%, 1%, 3%, 7%, 15%, and 20%), by weight in a fibrous form, have been prepared for experimental testing. X-ray diffraction and fluorescence analysis showed that exploited clay is suitable for construction purposes with a predominant quartz (SiO2) content. Collected findings showed that higher Typha-fiber proportions produced brick samples with higher porosity levels. The highest recorded porosity, 14.95%, was obtained with the incorporation of a 20% additive, compared to a 1.14% porosity percentage for reference samples. This resulted in the production of more porous bricks with improved thermal properties. In fact, at a 20% Typha-fibers additive content, 0.29 W/m·K and 0.76 kJ/kg·K respective thermal conductivity and specific heat capacity values were recorded, compared to 0.51 W/m·K and 0.59 kJ/kg·K at the reference samples. This represents 43% and 23% gains in thermal conductivity and specific heat capacity, respectively. A dynamic thermal inertia simulation was also carried out in the TRNSYS Type 56 software to evaluate the time lag and decrement factor parameters of prepared specimens as walling structures of a reference house. A total of 38% and 45% gains in the time lag and decrement factor were obtained with the incorporation of the highest additive proportion, 20%, compared to reference samples. Finally, four mathematical models are used to evaluate the thermal performance, in terms of thermal conductivity and specific heat capacity, of the studied specimens as a function of the measured porosity. The comparison drawn between the models’ theoretically predicted thermal properties and experimentally measured ones reflected a positive association between the two as the obtained correlation coefficient R was found to be very close to 1.

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