The Thermal Conductivity of Low Density Concretes Containing Perlite

Abstract

The thermal conductivity, k, of low density concretes made from Portland cement and perlite has been measured near room temperature using an unguarded linear heat flow apparatus. Perlite based concretes having densities from 44.3 lb/ft3 to 66.6 lb/ft3 were found to have thermal conductivities from 1.55 Btu·in/ft2 ·h·°F to 2.89 Btu·in/ft2 ·h·°F. The measured k can be correlated against density and the results agree with previously published results. The thermal resistance, R-value, of concrete blocks made with low density concretes and having core regions filled with perlite powder is calculated to be in the range of 7 to 12 ft2 ·h·°F/Btu. The material, therefore, has potential for energy conservation applications. The compressive strength of concretes generally decreases with density and this is true for the perlite products. The very low density concretes had measured compressive strengths below 500 lb /in2 and such material is unsuitable for many applications. Intermediate density products, however, have compressive strengths above 2000 lb /in2. Applications for the perlite concretes will, therefore, have to compromise between load bearing capability and energy conservation objectives.