Miloš Jerman

Free Water Intake as Means of Material Characterization

Free water intake experiment is analyzed from the point of view of the applicability of its output for material characterization. Several experimental setups are presented and discussed. Characteristic examples of sorptivity plots for different materials are given and their main features have been described. The application of the experiment for characterization of material damage and for explaining the water transport mechanisms in two-layer systems is presented. It is concluded that the free water intake experiment basically can be used as a means of material characterization but its strong and weak points should always be considered if conclusions on the behavior of a particular material are to be drawn.

Effective thermal conductivity of hollow bricks with cavities filled by air and expanded polystyrene

Effective thermal conductivity of hollow bricks with the cavities filled by either air or expanded polystyrene is analyzed using a hybrid experimental–computational approach. The experimental setup involves an application of a thermal insulation box and a set of temperature and heat flux probes placed at characteristic positions of the specimen-insulating box system. Using the measured heat fluxes and temperatures, the heat loss of the system is determined. A computer simulation tool based on the finite element principle is then used for modeling the temperature fields and heat losses in the studied system. Finally, the effective thermal conductivity is identified using an iterative procedure. Experimental results show that the application of expanded polystyrene as cavity filler instead of air leads to ∼30% decrease in the effective thermal conductivity of hollow brick blocks.

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.

Identification of Water Diffusivity of Inorganic Porous Materials Using Evolutionary Algorithms

Two evolutionary algorithms are introduced as universal approaches for the identification of water transport characteristics of inorganic porous materials in both absorption and desorption phases. At first, genetic algorithm and genetic programming are applied for the inverse analysis of water content profiles measured in an absorption experiment. A comparison of results with the output of the commonly used Boltzmann–Matano approach shows that the calculated diffusivities can reproduce experimental data with a similarly good or even slightly better accuracy. In the second part of investigations, a water desorption experiment is realized for autoclaved aerated concrete, a typical representative of inorganic porous materials used in the construction sector. The genetic algorithm and genetic programming exhibit an excellent performance also in this case. Both approaches can thus be considered as viable, more universal alternatives to the traditional methods.

Moisture diffusivity of wood

Moisture transport in four different types of wood is investigated. The specimens are subjected to one-sided water penetration in vertical direction and the moisture profiles are determined by the capacitance method. The calibration is done a posteriori using the last measured moisture profile by the gravimetric method. The moisture diffusivity is then determined as a function of moisture content using inverse analysis of moisture profiles.

Influence of weather-affected material characteristics on appearance of freeze/thaw cycles in building envelopes

The possible appearance of freeze/thaw cycles in external wall made of selected building material is assessed within this paper. Main objective of the presented research is to investigate the influence of weather-affected material characteristics on that phenomenon. For this sake, the samples were exposed to long-term weathering while the material characteristics were determined in the beginning of the experiment and then after two and three years. The comparative simulations of coupled heat and moisture transport inside the wall when exposed to dynamic climatic conditions were subsequently performed using reference and weather affected data. The results revealed that hygric parameters of the material, in particular, got worse which led also to deterioration of hygrothermal performance of the studied construction. The time of wetness under the external surface was twice as high when weather-affected data had been assumed. The number of possible freeze/thaw cycles was higher as well.

Computational analysis of a modified guarded hot plate experiment

A combined experimental-numerical approach for determination of apparent thermal conductivity of nonhomogenous large blocks, such as hollow clay bricks, is presented. In the first part, the input parameters (temperatures, heat fluxes) are measured. In the subsequent numerical analysis, errors in measurement given by heat losses are corrected and apparent thermal conductivity is evaluated.

Interior thermal insulation systems for historical building envelopes

The design specifics of interior thermal insulation systems applied for historical building envelopes are described. The vapor-tight systems and systems based on capillary thermal insulation materials are taken into account as two basic options differing in building-physical considerations. The possibilities of hygrothermal analysis of renovated historical envelopes including laboratory methods, computer simulation techniques, and in-situ tests are discussed. It is concluded that the application of computational models for hygrothermal assessment of interior thermal insulation systems should always be performed with a particular care. On one hand, they present a very effective tool for both service life assessment and possible planning of subsequent reconstructions. On the other, the hygrothermal analysis of any historical building can involve quite a few potential uncertainties which may affect negatively the accuracy of obtained results.

Characterization Of Fine-grained Ceramic Material For Environmental-friendly Applications In The Building Sector

A characterization of the properties of waste ceramic powder that is generated during advanced hollow brick production is presented. The main aim of the study is to facilitate environmental-friendly applications of the ceramic in the building sector. Therefore, its reactivity with cement is analyzed using isothermal calorimetry. Experimental results show that the investigated waste fine-grained ceramic material has good potential in application in concrete mix design from both environmental and economical perspectives.

Experimental Determination of Material Characteristics of New Type of Plaster

New type of commercial plaster which is not well known in the market is investigated in this paper. It is a new product delivered from Turkey, contains 80% of perlit, the binder is unknown and according to the producer it is some type of polymer. According to the producer’s data, the open porosity is 80% and the main advantages are good thermal and mechanical properties. The data in the technical data sheet are not complete, some important information is missing, therefore the basic physical, mechanical, thermal and hygric properties were studied in this paper. Moisture diffusivity, thermal conductivity and specific heat capacity are determined as a function of moisture content. Obtained data were compared with ordinary lime-cement plaster. The results can be further utilized in the computer simulation for service life assessment studies.