Coupled water and nitrate transport in dry cement mortar specimens is analyzed in the paper. In t... more Coupled water and nitrate transport in dry cement mortar specimens is analyzed in the paper. In the experimental part, the NaNO 3 solution penetration into cement mortar is investigated and the moisture content and nitrate concentration profiles are measured in three chosen time intervals. Then an inverse analysis of the profiles is performed to identify the transport parameters. It is found that advection is the main mechanism of nitrate transport in the studied case. The diffusion in the solution is much slower so that it is not capable to replace the ions bound on the pore walls.
In this paper, a 2-D critical experiment for the assessment of hygrothemal function of hydrophili... more In this paper, a 2-D critical experiment for the assessment of hygrothemal function of hydrophilic mineral wool based interior insulation system is presented. The described experiment is carried out utilizing a specially designed simulating and measuring technology for the analysis of hygrothermal performance of multi-layered building structures in the difference climate conditions. In the semi-scale experiment, the dimensions of the tested specimens are the same as in the real structure. For the climatic data on the exterior side the TRY data for Prague are used. Temperature and relative humidity data typical for residential buildings are assumed on the interior side. In the tested structure, relative humidity, moisture and temperature fields are monitored. Measured field variables are discussed and the functionality of the designed thermal insulaiton system is verified.
Thermal conductivity and specific heat capacity of several types of granular agricultural product... more Thermal conductivity and specific heat capacity of several types of granular agricultural products, namely of spring oat, wheat mixture Axis, barley mixture Expres, corn mixture and soybean Evans is measured in dependence on moisture content from the dry state to the water fully saturated state. An impulse technique is used for the measurement. The obtained results will find use in the selection of suitable methods for processing of agricultural products, in a qualified assessment of optimal modes of technological processes, and in the development of modern fully automatic agricultural equipments.
A semi-scale experimental analysis of hygrothermal performance of a building envelope in the cond... more A semi-scale experimental analysis of hygrothermal performance of a building envelope in the conditions of difference climate is performed to support computational modeling of heat and moisture transport in climatically loaded building structures. A computational analysis of the same envelope is done using the computer code Delphin 4.3, and the calculated data are compared with the measurements. The observed differences are discussed and recommendations for the improvement of computer modeling process are given.
Service life assessment of three historical building envelopes constructed using different types ... more 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.
Salts and water are assumed to damage historical masonries. Therefore, many conservation treatmen... more Salts and water are assumed to damage historical masonries. Therefore, many conservation treatments have been developed by research teams for the consolidation and protection of porous building materials affected by salt attack. Among them, different methods for obtaining effective desalination of historical masonry were proposed, having smaller or bigger disadvantages. Cellulose is the favourite material added to poultices used in desalination, and hydrophilic mineral wool (HMW) is considered as a possible alternative. Thanks to its hydrophilic additive, HMW allows water transport along the fibres, but contrary to cellulose it is an inorganic material, which reduces the maintenance of the poultice. In this paper, behaviour of the hydrophilic additive in relation to the wetting-drying cycles is studied. Basic characterization of the HMW is performed. Water and chloride absorption coefficients are measured using standard free water uptake experiment. Additionally, moisture profiles are accessed using gravimetric method, and the moisture diffusivity as a function of moisture content is calculated using an inverse analysis procedure. The measurements are performed on samples pretreated several times in water and 1M NaCl water solution. Finally, FTIR and chromatographic analyses of HMW leached in water were performed to verify the assumed leachability of the hydrophilic additive. The measured water and NaCl water solution transport parameters confirm that HMW can be used in building materials desalination; the observed drop in the water absorption coefficient is explained using the FTIR results.
The Boltzmann transformation method is used to determine the liquid water diffusivity from moistu... more The Boltzmann transformation method is used to determine the liquid water diffusivity from moisture content profiles as measured in a capillary water absorption experiment. An inter-laboratory comparison for analyzing the reliability of the determination method showed that the inaccuracy in the liquid water diffusivity is caused by scatter in the transformed data and by uncertainty in the boundary conditions at the intake surface and ahead of the steep moisture front. A methodology is proposed based on (1) the evaluation of the validity of the diffusion approach, (2) a simplified handling of the boundary conditions, (3) smoothing of the scattered data and (4) the evaluation of the quality of the determined liquid water diffusivity. For HAM (Heat-Air-Moisture transport) calculations values of the liquid water diffusivity for moisture contents higher than the capillary moisture content are disregarded. The liquid water diffusivity can be described by an exponential function limited at a lower moisture content bound.
The effect of moisture content on the thermal conductivity of lime-based composites is investigat... more The effect of moisture content on the thermal conductivity of lime-based composites is investigated both experimentally and theoretically. Experimental measurements of thermal conductivity as a function of moisture content from a dry state to a fully water saturated state are performed using an impulse technique. The obtained experimental data are analyzed at first with fundamental theoretical models, and it is found that they conform to both Wiener's and Hashin-Shtrikman's bounds. The thermal conductivity of wet lime-based composites is then analyzed using several homogenization techniques, among them, Lichtenecker's, Polder and van Santen's, and Dobson's formulas. The validity of applied effective-media treatments is assessed comparing the measured and calculated data. Lichtenecker's equation is found to achieve the best agreement with experimental measurements.
The measurements of thermal conductivity of a cement-based composite material are performed in de... more The measurements of thermal conductivity of a cement-based composite material are performed in dependence on moisture content from dry state to fully water saturated state using an impulse technique. Then, the obtained data are analyzed using Brugemann and Wiener homogenization formulas. The validity of applied homogenization techniques is assessed comparing the measured and calculated results. On the basis of the experimental data and the homogenization analyses, the effects of total pore volume, pore distribution and moisture content on the thermal conductivity are discussed.
Coupled water and chloride transport in cement mortar is analyzed experimentally in the paper. Sa... more Coupled water and chloride transport in cement mortar is analyzed experimentally in the paper. Samples with initial moisture content corresponding to 45% relative humidity are subjected to one-sided sodium chloride-in-water solution uptake, and moisture profiles and chloride concentration profiles are determined in three chosen time intervals. In the evaluation of measured moisture profiles and chloride concentration profiles, diffusion model is employed. Moisture diffusivity is determined as function of moisture content and chloride diffusion coefficient as function of chloride concentration using two methods commonly used for analysis of moisture profiles, namely the double integration method and the Matano method. The highest values of both coefficients are obtained by Matano method for the curves corresponding to 24 h exposure to the solution, the lowest values by Matano method for 168 h, the results obtained by double integration method are in between. The complementary experiments with distilled water as penetrating liquid performed for the sake of comparison do not show this feature. It is observed that water transport in the initial time period is for the chloride solution faster and in later times slower than for distilled water. Therefore, the observed differences in the calculated apparent values of moisture diffusivity and chloride concentration coefficients are attributed to the fact that Cl À and Na þ ions are adsorbed on the pore walls faster than water molecules. This effect should be included into the mathematical models using ion binding isotherms.
Experimental analysis of a wide range of properties of a lightweight plaster which should enhance... more Experimental analysis of a wide range of properties of a lightweight plaster which should enhance the heat-storage capacity of building envelopes is presented. The basic physical characteristics, namely, the bulk density, matrix density, total open porosity, and pore-size distribution are measured at first. Then, the compressive strength is determined for an assessment of mechanical performance of the plaster. The thermal conductivity and thermal diffusivity are studied using an impulse technique. Differential scanning calorimetry measurements are performed as well, in order to identify the temperature range and latent heat of the phase change and to determine the specific heat capacity as a function of temperature. Durability properties are assessed using the measurement of the water absorption coefficient and sorption and desorption isotherms. The experimental results indicate a good capability of the designed plaster to moderate effectively the interior climate of buildings.
An inverse analysis of coupled water and salt transport in porous materials is presented in the p... more An inverse analysis of coupled water and salt transport in porous materials is presented in the paper. For the description of salt solution transport, the diffusion-advection model taking into account the influence of water movement on salt transport and the salt bonding on pore walls is used. The inverse analysis is performed for the samples of cement mortar. As a result, moisture diffusivity as function of moisture content and chloride diffusion coefficient as function of concentration are obtained.
A computational assessment of water and salt transport parameters describing the coupled moisture... more A computational assessment of water and salt transport parameters describing the coupled moisture and chloride transport in porous media is presented in this paper. The experimentally determined moisture profiles, chloride concentration profiles and chloride binding isotherm are subjected to inverse analysis where three different modes of salt solution transport are assumed. On the basis of this analysis, moisture dependent moisture diffusivity and salt concentration dependent chloride diffusion coefficient are calculated. The obtained results can find use in computational modelling of salt transport in porous building materials which is currently a very important topic, particularly from the point of view of durability of building materials and service life of building structures exposed to salt attack. Keywords: moisture diffusivity, salt diffusion coefficient, chloride binding isotherm. 1 Introduction The durability and service life assessment of building materials and structures...
Coupled water and nitrate transport in dry cement mortar specimens is analyzed in the paper. In t... more Coupled water and nitrate transport in dry cement mortar specimens is analyzed in the paper. In the experimental part, the NaNO 3 solution penetration into cement mortar is investigated and the moisture content and nitrate concentration profiles are measured in three chosen time intervals. Then an inverse analysis of the profiles is performed to identify the transport parameters. It is found that advection is the main mechanism of nitrate transport in the studied case. The diffusion in the solution is much slower so that it is not capable to replace the ions bound on the pore walls.
In this paper, a 2-D critical experiment for the assessment of hygrothemal function of hydrophili... more In this paper, a 2-D critical experiment for the assessment of hygrothemal function of hydrophilic mineral wool based interior insulation system is presented. The described experiment is carried out utilizing a specially designed simulating and measuring technology for the analysis of hygrothermal performance of multi-layered building structures in the difference climate conditions. In the semi-scale experiment, the dimensions of the tested specimens are the same as in the real structure. For the climatic data on the exterior side the TRY data for Prague are used. Temperature and relative humidity data typical for residential buildings are assumed on the interior side. In the tested structure, relative humidity, moisture and temperature fields are monitored. Measured field variables are discussed and the functionality of the designed thermal insulaiton system is verified.
Thermal conductivity and specific heat capacity of several types of granular agricultural product... more Thermal conductivity and specific heat capacity of several types of granular agricultural products, namely of spring oat, wheat mixture Axis, barley mixture Expres, corn mixture and soybean Evans is measured in dependence on moisture content from the dry state to the water fully saturated state. An impulse technique is used for the measurement. The obtained results will find use in the selection of suitable methods for processing of agricultural products, in a qualified assessment of optimal modes of technological processes, and in the development of modern fully automatic agricultural equipments.
A semi-scale experimental analysis of hygrothermal performance of a building envelope in the cond... more A semi-scale experimental analysis of hygrothermal performance of a building envelope in the conditions of difference climate is performed to support computational modeling of heat and moisture transport in climatically loaded building structures. A computational analysis of the same envelope is done using the computer code Delphin 4.3, and the calculated data are compared with the measurements. The observed differences are discussed and recommendations for the improvement of computer modeling process are given.
Service life assessment of three historical building envelopes constructed using different types ... more 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.
Salts and water are assumed to damage historical masonries. Therefore, many conservation treatmen... more Salts and water are assumed to damage historical masonries. Therefore, many conservation treatments have been developed by research teams for the consolidation and protection of porous building materials affected by salt attack. Among them, different methods for obtaining effective desalination of historical masonry were proposed, having smaller or bigger disadvantages. Cellulose is the favourite material added to poultices used in desalination, and hydrophilic mineral wool (HMW) is considered as a possible alternative. Thanks to its hydrophilic additive, HMW allows water transport along the fibres, but contrary to cellulose it is an inorganic material, which reduces the maintenance of the poultice. In this paper, behaviour of the hydrophilic additive in relation to the wetting-drying cycles is studied. Basic characterization of the HMW is performed. Water and chloride absorption coefficients are measured using standard free water uptake experiment. Additionally, moisture profiles are accessed using gravimetric method, and the moisture diffusivity as a function of moisture content is calculated using an inverse analysis procedure. The measurements are performed on samples pretreated several times in water and 1M NaCl water solution. Finally, FTIR and chromatographic analyses of HMW leached in water were performed to verify the assumed leachability of the hydrophilic additive. The measured water and NaCl water solution transport parameters confirm that HMW can be used in building materials desalination; the observed drop in the water absorption coefficient is explained using the FTIR results.
The Boltzmann transformation method is used to determine the liquid water diffusivity from moistu... more The Boltzmann transformation method is used to determine the liquid water diffusivity from moisture content profiles as measured in a capillary water absorption experiment. An inter-laboratory comparison for analyzing the reliability of the determination method showed that the inaccuracy in the liquid water diffusivity is caused by scatter in the transformed data and by uncertainty in the boundary conditions at the intake surface and ahead of the steep moisture front. A methodology is proposed based on (1) the evaluation of the validity of the diffusion approach, (2) a simplified handling of the boundary conditions, (3) smoothing of the scattered data and (4) the evaluation of the quality of the determined liquid water diffusivity. For HAM (Heat-Air-Moisture transport) calculations values of the liquid water diffusivity for moisture contents higher than the capillary moisture content are disregarded. The liquid water diffusivity can be described by an exponential function limited at a lower moisture content bound.
The effect of moisture content on the thermal conductivity of lime-based composites is investigat... more The effect of moisture content on the thermal conductivity of lime-based composites is investigated both experimentally and theoretically. Experimental measurements of thermal conductivity as a function of moisture content from a dry state to a fully water saturated state are performed using an impulse technique. The obtained experimental data are analyzed at first with fundamental theoretical models, and it is found that they conform to both Wiener's and Hashin-Shtrikman's bounds. The thermal conductivity of wet lime-based composites is then analyzed using several homogenization techniques, among them, Lichtenecker's, Polder and van Santen's, and Dobson's formulas. The validity of applied effective-media treatments is assessed comparing the measured and calculated data. Lichtenecker's equation is found to achieve the best agreement with experimental measurements.
The measurements of thermal conductivity of a cement-based composite material are performed in de... more The measurements of thermal conductivity of a cement-based composite material are performed in dependence on moisture content from dry state to fully water saturated state using an impulse technique. Then, the obtained data are analyzed using Brugemann and Wiener homogenization formulas. The validity of applied homogenization techniques is assessed comparing the measured and calculated results. On the basis of the experimental data and the homogenization analyses, the effects of total pore volume, pore distribution and moisture content on the thermal conductivity are discussed.
Coupled water and chloride transport in cement mortar is analyzed experimentally in the paper. Sa... more Coupled water and chloride transport in cement mortar is analyzed experimentally in the paper. Samples with initial moisture content corresponding to 45% relative humidity are subjected to one-sided sodium chloride-in-water solution uptake, and moisture profiles and chloride concentration profiles are determined in three chosen time intervals. In the evaluation of measured moisture profiles and chloride concentration profiles, diffusion model is employed. Moisture diffusivity is determined as function of moisture content and chloride diffusion coefficient as function of chloride concentration using two methods commonly used for analysis of moisture profiles, namely the double integration method and the Matano method. The highest values of both coefficients are obtained by Matano method for the curves corresponding to 24 h exposure to the solution, the lowest values by Matano method for 168 h, the results obtained by double integration method are in between. The complementary experiments with distilled water as penetrating liquid performed for the sake of comparison do not show this feature. It is observed that water transport in the initial time period is for the chloride solution faster and in later times slower than for distilled water. Therefore, the observed differences in the calculated apparent values of moisture diffusivity and chloride concentration coefficients are attributed to the fact that Cl À and Na þ ions are adsorbed on the pore walls faster than water molecules. This effect should be included into the mathematical models using ion binding isotherms.
Experimental analysis of a wide range of properties of a lightweight plaster which should enhance... more Experimental analysis of a wide range of properties of a lightweight plaster which should enhance the heat-storage capacity of building envelopes is presented. The basic physical characteristics, namely, the bulk density, matrix density, total open porosity, and pore-size distribution are measured at first. Then, the compressive strength is determined for an assessment of mechanical performance of the plaster. The thermal conductivity and thermal diffusivity are studied using an impulse technique. Differential scanning calorimetry measurements are performed as well, in order to identify the temperature range and latent heat of the phase change and to determine the specific heat capacity as a function of temperature. Durability properties are assessed using the measurement of the water absorption coefficient and sorption and desorption isotherms. The experimental results indicate a good capability of the designed plaster to moderate effectively the interior climate of buildings.
An inverse analysis of coupled water and salt transport in porous materials is presented in the p... more An inverse analysis of coupled water and salt transport in porous materials is presented in the paper. For the description of salt solution transport, the diffusion-advection model taking into account the influence of water movement on salt transport and the salt bonding on pore walls is used. The inverse analysis is performed for the samples of cement mortar. As a result, moisture diffusivity as function of moisture content and chloride diffusion coefficient as function of concentration are obtained.
A computational assessment of water and salt transport parameters describing the coupled moisture... more A computational assessment of water and salt transport parameters describing the coupled moisture and chloride transport in porous media is presented in this paper. The experimentally determined moisture profiles, chloride concentration profiles and chloride binding isotherm are subjected to inverse analysis where three different modes of salt solution transport are assumed. On the basis of this analysis, moisture dependent moisture diffusivity and salt concentration dependent chloride diffusion coefficient are calculated. The obtained results can find use in computational modelling of salt transport in porous building materials which is currently a very important topic, particularly from the point of view of durability of building materials and service life of building structures exposed to salt attack. Keywords: moisture diffusivity, salt diffusion coefficient, chloride binding isotherm. 1 Introduction The durability and service life assessment of building materials and structures...
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