Effect of expanded vermiculite and expanded perlite as pore forming additives on the physical properties and thermal conductivity of porous clay bricks
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2018-01-01
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Abstract
The way to achieve better energy efficiency in buildings is to improve their thermal insulation properties. This can be done by increasing the porosity of the clay bricks by introducing pore-forming additives to the clay or production of perforated bricks. In general, thermal conductivity of the bulk clay bricks is about 1.0 W/mK depending on their raw materials, processing, firing temperatures and fired densities. These values can be reduced by addition of various inorganic and organic pore-forming agents into the brick raw material mixtures before firing. This paper presents the effect of adding of expanded vermiculite and expanded perlite in quantity of 0, 3, 5 and 8 mass % on the physical properties and thermal conductivity of clay porous bricks fired at 900oC for 2 hours. Expanded vermiculite and expanded perlite were selected as pore former as they have very low density and good thermal insulation properties. The results show an increasing of water absorption and apparent porosity compared t? fired pure clay bricks and lower thermal conductivity of the fired at 900oC products with expanded vermiculite and expanded perlite. At small amounts of pore former, the properties of the fired clay materials slightly changed and more pronounced is the influence of vermiculite. Expanded vermiculite and expanded perlite in amount of 8 mass % can be used as a pore forming agents in bricks production to improve thermal conductivity of clay bricks and keep acceptable the compressive strength. Keywords: expanded vermiculite, expanded perlite, porous clay bricks, porosity, thermal conductivity.