Experimental investigation of the effect of moisture on thermal conductivity and specific heat of porous ceramic materials

Thermal conductivity and specific heat of porous ceramic materials display a unique behaviour when moisture is present in their structure. When compared with the corresponding dried materials, these properties are drastically altered, and the magnitude of these changes depends on the moisture content. In this work it was experimentally investigated the effect of adsorbed water on the thermal conductivity and specific heat of the most commonly structural material: castables and concrete of Portland cement. The experimental technique employed was the hot wire parallel technique, and measurements were carried out from room temperature up to 300 degrees C during the heating and cooling cycle. The thermal conductivity and the specific heat were simultaneously determined from the same experimental thermal transient. Experimental results show a drastic influence of the adsorbed water on the thermal conductivity and specific heat of green castables. It was also observed that the addition of glassy phase on sample composition decreases the thermal conductivity and promotes the inversion of the slope of the curve thermal conductivity versus temperature for the dried material. (C) 2000 Kluwer Academic Publishers.