The Effect of Physical Properties on Thermal Conductivity of Lightweight Aggregate

There are many studies about the thermal conductivity coefficient of lightweight concrete using lightweight aggregates such as perlite, pumice, vermiculite, diatomite earth and expanded clay aggregates. However, researches related to the thermal conductivity of lightweight aggregates is limited. The lightweight aggregates are the main raw materials of lightweight construction material. In addition, the usability of lightweight aggregates as core material has been investigated in recent years. Thermal conductivity of lightweight aggregates significantly affects the thermal insulation performance of such composites. The thermal conductivity coefficients of lightweight aggregates are related to many of the physical properties of aggregates such as specific gravity, porosity, particle size etc. In this study, the effects of loose unit weight, the volume of aggregate matrix, porosity and grain size on the thermal conductivity of lightweight aggregates was investigated. Limestone aggregate (normal aggregate) was also used for comparison in the study.At first, all of the aggregates were divided into 4 different grain groups (2-1 mm, 1-0.5 mm, 0.5-0.1 mm and <0.1 mm). The specific gravity, oven-dry particle density and loose unit weight values of aggregates were determined according to TS 699 and TS EN 1097-6 standards for each grain group, then the open and closed pore rates of aggregates were calculated with obtained data. Next, the aggregates were dried up until it reached a constant weight. Afterwards, the thermal conductivity coefficients at atmospheric pressure of the lightweight aggregates were measured according to the TS EN 12664 standard. By analyzing data, the thermal conductivity coefficients of lightweight aggregates were associated with their physical properties. As a result, an empirical formula was proposed in order to estimate the thermal conductivity coefficient depending on the physical properties of lightweight aggregates.