A comparative study on the thermal conductivities and mechanical properties of lightweight concretes

Thermal conductivity of the materials used in buildings is one of the major factors affecting the heat transfer. Higher thermal conductivity of building walls results in higher heat losses, and in order to maintain the same temperature inside a building, energy consumption for heating or cooling increases. To reduce the heat loss, thus decrease the energy usage, materials with lower thermal conductivities should be preferred. Lightweight concretes can be used for this purpose. However, the properties of these concretes may vary depending on the materials used. The main objective of this experimental study is to compare the properties of lightweight concretes produced with different lightweight aggregates. Lightweight concretes in a wide range of unit weights from approximately 300-1800 kg/m3 were prepared in the experimental program. Some properties of the concretes containing pumice and expanded polystyrene beads were obtained. Properties of concretes with expanded perlite and autoclaved aerated concrete determined in previous studies are also included in comparisons and discussion. The test results showed that, depending on the amount and type of lightweight aggregate, unit weight of concrete can be reduced and concretes with various physical and mechanical properties of can be achieved. Thermal conductivity was reduced with the use of lightweight aggregates and for all the lightweight concretes considered, a good relationship was obtained between thermal conductivity and unit weight of concrete. Reductions in the compressive strength and modulus of elasticity of concretes have been obtained with decreasing concrete unit weights. The reduction in strength was more for the concrete containing expanded polystyrene beads.Results showed that strong relationships exist between modulus of elasticity and unit weight of concrete. Results showed that strong relationships exist between modulus of elasticity and unit weight of concrete.