Convegni ATI - Accesso riservato soci CTI

Autore: J. Toman, R. Cerny

Collana: CA - 49 - Perugia 1994

Note:
A method for measuring the coupled influences of temperature and moisture on the linear thermal expansion of porous materials is proposed in the paper. The method is based in the length measurements using a comparator and on an application of the superposition principle to the relative elongation due to temperature and moisture changes. The application of the proposed method is illustrated on four typical heat-insulating building materials, Dekalit P, Dekalux, Orsil WV and Orsil WD. Measured results show a significant influence of the rate of moistening and drying as well as the moistening method itself on the linear expansion of Dekalit P and Dekalux. The differences in linear moisture expansion coefficient of Dekalit P caused by these effects can achieve several hundred of per cents. On the contrary, no moisture influence on the linear expansion is observed for Orsil WV and Orsil WD which is due to a very low content of moisture in this type of materials. The thermal expansion behaviour of all studied materials except Dekalux is found to be regular, the linear thermal expansion coefficient being constant in the temperature range of -30°C to 180°C. Dekalux exhibits shrinking with the temperature increase for T > 80°C. Generally, the influence of moisture on linear expansion is for Dekalit P and Dekalux more important then the influence of temperature, for both Orsils is the temperature influence dominant.