Jaromír Žumár

Water Vapor Adsorption in Porous Building Materials: Experimental Measurement and Theoretical Analysis

An experimental and theoretical analysis of the water vapor adsorption in several types of porous building materials is presented. For the measurement of adsorption isotherms, a DVS-Advantage water sorption device is used. The experimental data is analyzed using theoretical formulas based on the BET, BSB, BDDT, and FHH isotherms, assuming a mono as well as multi-layer water vapor adsorption. The BSB equation is found to provide a good approximation for the relative humidities below 0.6–0.7, whereas the FHH equation shows a sufficient accuracy for the relative humidities above 0.4–0.5. Based on a combination of BSB and FHH isotherms, a semi-empirical formula is proposed that allows one to obtain a very accurate approximation of experimental data for all analyzed materials and all values of the relative humidity.

Service Life Assessment of Historical Building Envelopes Constructed Using Different Types of Sandstone: A Computational Analysis Based on Experimental Input Data

Service life assessment of three historical building envelopes constructed using different types of sandstone is presented. At first, experimental measurements of material parameters of sandstones are performed to provide the necessary input data for a subsequent computational analysis. In the second step, the moisture and temperature fields across the studied envelopes are calculated for a representative period of time. The computations are performed using dynamic climatic data as the boundary conditions on the exterior side of building envelope. The climatic data for three characteristic localities are experimentally determined by the Czech Hydrometeorological Institute and contain hourly values of temperature, relative humidity, rainfalls, wind velocity and direction, and sun radiation. Using the measured durability properties of the analyzed sandstones and the calculated numbers of freeze/thaw cycles under different climatic conditions, the service life of the investigated building envelopes is assessed. The obtained results show that the climatic conditions can play a very significant role in the service life assessment of historical buildings, even in the conditions of such a small country as the Czech Republic. In addition, the investigations reveal the importance of the material characteristics of sandstones, in particular the hygric properties, on their service life in a structure.

Application of genetic algorithm for determination of water vapor diffusion parameters of building materials

A combined experimental/computational technique for determination of water vapor transport properties of porous building materials based on the application of genetic algorithm is developed and tested on cellular concrete. The method allows obtaining water vapor transport properties in dependence on relative humidity which is a crucial factor for advanced computational modeling of hygrothermal performance of multi-layered systems of building materials. Moreover, in a comparison with the standard steady-state cup method, the presented technique requires less than half of the time necessary for measurement which, makes good prerequisites for its wider application in materials research.

Application of waste ceramic dust as a ready-to-use replacement of cement in lime-cement plasters: an environmental-friendly and energy-efficient solution

A potential application of waste ceramic dust as cement replacement in lime-cement plasters is studied using both experimental and computational approaches. A comprehensive experimental analysis of the material properties of lime-cement plaster and three lime-pozzolan plasters containing different amounts of waste ceramics is performed at first. The results show that compressive strength of ceramics-containing plasters can be up to three times higher as compared with the lime-cement plaster but their thermal conductivity is higher as well. In the second part of the study, the hygrothermal and energy performance of a characteristic building envelope provided with the four analyzed plasters as surface layers is analyzed. The results of numerical simulations reveal that the application of waste ceramic dust in lime-pozzolan plasters does not have a negative effect on both the hygrothermal and energy performance of the building envelope, as compared with the use of lime-cement plaster. Taking into account the energy demand and environmental load related to cement production, the application of waste ceramic dust as a ready-to-use replacement of cement in lime-cement plasters represents the right step toward sustainable development.

A Boltzmann transformation method for investigation of water vapor transport in building materials

A Boltzmann transformation method that allows determination of water vapor transport properties of building materials as functions of relative humidity during a single experiment is presented. The method is tested at the laboratory measurements on autoclaved aerated concrete. Determination of diffusion coefficient by standard steady-state cup method is done as well, for the sake of comparison. The measured results are discussed with regard to the practical application of the method in materials research and building practice.

Effect of temperature on water vapor transport properties

The temperature effect on water vapor transport properties of calcium silicate is studied, together with the influence of sample thickness. For material characterization purposes, the bulk density, matrix density, and total open porosity are measured at first. Sorption and desorption isotherms are measured using dynamic vapor sorption device in order to characterize the water vapor storage in researched material. The sorption process is analyzed for original material samples as well as for finely ground samples in order to evaluate the effect of inner porous space on water vapor storage. The steady state cup method is used for determination of water vapor transport properties, whereas the measurements are performed at several temperatures and for three different sample thicknesses. The obtained data show an important effect of temperature on water vapor transport and storage in studied material. The results also indicate a substantial influence of sample thickness on the calculated water vapor transmission properties.

Effect of heat and moisture transport and storage properties of building stones on the hygrothermal performance of historical building envelopes

The heat and moisture transport and storage parameters of three different natural stones used on the Czech territory since medieval times are determined experimentally, together with the basic physical properties and mechanical parameters. The measured data are applied as input parameters in the computational modeling of hygrothermal performance of building envelopes made of the analyzed stones. Test reference year climatic data of three different locations within the Czech Republic are used as boundary conditions on the exterior side. Using the simulated hygric and thermal performance of particular stone walls, their applicability is assessed in a relation to the geographical and climatic conditions. The obtained results indicate that all three investigated stones are highly resistant to weather conditions, freeze/thaw cycles in particular.

Water Vapor Diffusion and Adsorption of Sandstones: Influence of Rock Texture and Composition

The term sandstone is used for wide range of rocks containing quartz clasts which can be cemented by secondary precipitated quartz or calcite; moreover the space between clasts can be filled by matrix. These facts result in existence of numerous rocks having highly various properties. Sandstones have been used as construction materials due to their good accessibility and workability. Since most of sandstones are porous, water vapor can penetrate through sandstone constructions. The rate of water vapor diffusion, as well as the vapor sorption isotherm, was determined for range of sandstone types. The diffusion resistance factor was found to be dependent on the total porosity of sandstone but the sorption behavior was strongly influenced by nature of the particular sandstone; the specific surface area of stone and presence of clay matrix are determining its sorption isotherm. The published data enable estimating (i) diffusion resistance factor of a sandstone via knowledge of its total porosity and (ii) the sorption isotherm via knowledge of the stone’s nature and specific surface area. This approach can significantly reduce the time necessary to acquire vapor-related properties of a sandstone.

MONITORING THE DAMAGE OF EXTERIOR RENDERS CAUSED BY THE ENVIRONMENT

Three renders commonly used in the Czech Republic on the exterior side of building envelopes are exposed for 2 years to the environmental conditions of the city of Prague. The effect of external environment on their possible damage is monitored using the measurement of a variety of material properties in selected time intervals. The experimental results do not show any significant deterioration of most parameters during the 2-year investigation period. The open porosity is found to decrease with time due to the continuing hardening processes. The mechanical properties are thus improved after 1 year of exposition and only little worsened after the second year. The changes in the pore structure also result in deceleration of waterand water-vapor transport and a slight increase of thermal conductivity. The obtained results will serve as reference data for finding a correlation between the accelerated laboratory tests and the behavior of analyzed materials in real building structures.

A Contribution to the Analysis of Water Vapor Transport in Porous Building Materials

The suitability of a water vapor transport parameter determined by the cup method for the description of water vapor transport in porous building material is analyzed in the paper. The relative humidity profiles are measured by a transient method with different water vapor pressure gradients. Moisture profiles calculated using a mathematical model are compared with the measured profiles. The goodness-of-fit tests are calculated for different experimental setups. The possibility of application of the analyzed water vapor transport parameter is discussed.