Dual Band Infrared Thermography as a NDT Tool for the Characterization of the Building Materials and Conservation Perfor
- PDF / 2,401,235 Bytes
- 6 Pages / 414.72 x 639 pts Page_size
- 76 Downloads / 156 Views
In previous works [1,2], it has been proved that water absorption by capillarity and evaporation phenomena control the weathering effects in porous media and produce damages like salt decay on heterogeneous systems like historic masonries. The study of vapor/moisture transport phenomena in porous building materials is critical to understand the respiration behavior and weathering of such materials. Incompatible capillary systems like in heterogeneous material systems, such as historic masonries, have been proved to undergo differentiated weathering processes and rates, which produce intensified damage to the weaker materials [3]. Infrared thermography has been used to detect in situ differential weathering performance of building materials in real scale [4]. The temperature differences detected by IR Thermography were up to now interpreted by the differences of the microstructural characteristics of the materials and the consequently retained humidity contents, studied as equilibrium phenomena [5] under steady environmental (Relative humidity and temperature) conditions [6]. However, the rate of the capillary absorption of water, as well as, the evaporation rate, regarding the dynamic study of materials of the water/vapor transport phenomena in the porous systems is fundamental, for the interpretation of the thermographs in real time on real scale systems. In the present work, the interpretation of the in situ IR Thermographs is attempted by the study of humidity gradation and distribution in real time in building materials and simulating masonry prototypes in lab. 169 Mat. Res. Soc. Symp. Proc. Vol. 5910 2000 Materials Research Society
EXPERIMENT (a) Experimental Procedures: (al) Short wave (Avio TVS-2300 MkII ST, 3-5.4pin), as well as long wave Infrared Thermography (Avio TVS-2000 MkII LW, 8-121im) were used, for the evaluation of the humidity distribution by capillary rise (absorption, evaporation) in reference samples of porous materials in the laboratory, in order to validate the examination of real scale material systems in situ. Infrared Thermography detects the radiation that a material emits and can render the image of the surface area in colors, in relation to a temperature scale, providing thermal maps. (a2) Capillary rise tests for the determination of the water absorption percentages and coefficients were performed in repair mortars and sandstone samples in a normalized sand bed apparatus. The water absorption coefficient was calculated as: CA= AB/S*t1/2 2
2
where: CA: (g*cm *s'U ), according to standard NORMAL 11/85 is: AB=B-BO: the length of the asymptotic value where the AB difference between the initial and the final weight of the
sample is less than 1%(g), S: the surface area of the sample contact in water (cm2), t: the time of the absorption resultant from the asymptotic length of AB and the tangential extrapolation of the linear part of the curve (s). Along with the capillary rise tests, the behavior of these samples and the simulating prototypes during evaporation is studied [2]. (b)Materi
Data Loading...
