MILENA PAVLÍKOVÁ, ZBYŠEK PAVLÍK, ROBERT ČERNÝ Department Materials Engineering and Chemistry Faculty Civil Engineering Czech Technical University in Prague
The functional sample Diffusion Tube is instrumental to the experimental assessment water vapour transport properties porous building materials in non-stationary state water vapour flux. In measuring the material parameters characterising the water vapour diffusion in porous building materials, the steady-state methods are the most commonly used. These methods are generally considered to be reliable and relatively accurate but they are usually time-consuming. Among steady-state methods, the cup method is the most frequently used in the practice as it is normalised in most countries over the world. Using this method, a single value water vapour diffusion coefficient, water vapour diffusion permeability or water vapour diffusion resistance factor can be accessed. Probably the main reason for its ten application represents its simplicity which minimizes the risk failure or substantial errors. Although the cup method has proved to be a very useful and reliable method in past decades, it is a steady-state method which has a very unpleasant feature that the time necessary for a single measurement may take several days or weeks. On this account, transient methods are more suitable for practical applications, if speeding up the experiment while keeping a comparably good accuracy to the cup method is necessary.
NONSTAT M. Pavlíková 1*, Z. Pavlík Functional 2* sample Diffusion Tube consists two airtight plexiglass *Czech Technical University chambers in Prague, separated Faculty by the Civil measured Engineering, sample. Each the Department Materials chambers Engineering is provided and Chemistry, with probes Czech for relative humidity Republic measurement working on capacitive principle. The size tested milena.pavlikova@fsv.cvut.cz, circular samples pavlikz@fsv.cvut.cz is 120 mm in diameter and 20 mm in thickness. Before the measurement, the studied material samples are dried at The functional sample vacuum NONSTAT drier. In the is chambers, instrumental environments to the with different relative experimental assessment humidity are hygrothermal maintained function using saturated building salt solutions with known materials and fragments values building equilibrium structures relative in humidity. the conditions close to the reality. For The example, studied saturated specimens K are within the 2 SO 4 water solution can be used for experimental testing simulation exposed relative to the humidity difference conditions climate close that to 90%. In the second corresponds to the real chamber, climatic a loading state close building to 10% structures. relative humidity The can be achieved functional sample NONSTAT using silica consists gel. Alternatively, two climatic relative chambers humidities and corresponding to connecting tunnel that the is placed dry-cup between and wet-cup the chambers methods and can serves be chosen. Within the for the samples placing. measurement, Usually, the 1-D changes analysis in mass hygrothermal the vessels behaviour containing is performed. However, also K the 2-D and 3-D experiments are possible. 2 SO 4 and silica gel placed in both chambers are recorded by Within the climatic loading, automatic moisture balances content, in dependence relative humidity, on time. These temperature data are and then salinity are monitored used in the as studied input specimen. parameters For that a mathematical purpose, sophisticated method designed for the calculation water vapour transport parameters.
Figure 1. Arrangement climatic chamber system and mechanical space climatic chamber. Figure 1. Functional sample for the transient measurement water vapour transport properties
Figure 2. Detail view the transient apparatus
Figure 3. Detail view the sample arrangement