Papers by Author: Jiří Maděra

Abstract: The presented paper aims at thorough uncertainty analysis of combined experimental and computational approach for determination of equivalent thermal conductivity of highly perforated bricks. The thermal conductivity is determined using experimental guarded hot plate method. However, due to large dimensions of analyzed specimens, the measurement is influenced by experimental errors due to abnormal heat leakage. Therefore, numerical modeling of heat transfer is performed in order to quantify this leakage and the resulting value of thermal conductivity is subsequently corrected. The uncertainty analysis is essential part of presented approach leading to its justification. It involves statistical errors, measurement errors as well as results of merged sensitivity analysis. Within the frame of this paper, highly perforated clay brick without cavity fillings was investigated. The results indicated that accuracy of presented approach is very sufficient and combined standard uncertainty is lower than 10 %.

Abstract: The in-situ examination of the historical enclosure wall of the Star Game Preserve located in the capital of the Czech Republic, Prague, is presented in the paper, in order to obtain necessary information for a qualified design of renovation and reconstruction treatments. At the visual inspection of the researched structure, the previous reconstruction methods are identified and evaluated, together with possible moisture sources. Moreover, the damage extent and propagation are assessed. Most of the oldest as well as newly constructed parts of the enclosure wall are found in bad condition and dilapidating. On this account, the building stone (arenaceous marl) forming the original historical masonry is examined to find compatible materials for the reconstruction works. Its chemical composition is accessed by X-Ray Fluorescence analysis. For the researched stone, basic physical, mechanical, hygric and thermal properties are measured. Using the obtained data, the proper material for reconstruction purposes will be identified.

Abstract: In situ analysis of hygrothermal state of the Sedlec Ossuary, Czech Republic, is presented in the paper. Within the experimental analysis, the measurement of moisture distribution in several profiles of historical masonry is done on a gravimetric principle. Non-destructive measurement of moisture content on the wall surface is done as well, using a capacitive moisture meter. Moreover, the interior and exterior climate is monitored over an almost two year period. On the basis of the obtained experimental results the hygrothermal conditions in both the masonry and the interior are assessed, including the identification of main moisture sources.

Abstract: This paper aims at computational simulation of effect of zeolite admixture on service life of concrete building envelope from point of view of freeze/thaw resistance. Hygrothermal behavior of two types of concrete is studied in this paper: reference concrete without any admixtures and zeolite concrete with 40 % zeolite as cement replacement. The computations are performed using computer simulation tool HEMOT, which processes the input parameters using finite element method. The simulation is assumed under dynamic climatic conditions of Prague. As the results of the computational simulations showed, assuming analyzed amount of zeolite, any positive effect of on freeze/thaw resistance was not found related to unprotected building envelope. However, the results indicated, hygrothermal performance of zeolite concrete can be very considerate to applied external layers and thus extend their service life.

Abstract: Lime plaster modified with pozzolana based on calcined kaoline mixed with mudstone and reference lime plaster are studied in the paper. For the studied materials, determination of bulk density, matrix density and total open porosity is done first. Then, specific attention is paid to the assessment of moisture diffusivity and chloride diffusion coefficient that are considered as decisive parameters for the materials’ durability. The measured data are used as input parameters for computational modeling of studied materials’ performance using computer code TRANSMAT 6.2 based on finite element computer simulation tool. On the basis of measured and calculated results, the applicability of newly developed plaster for renewal of historical buildings is discussed.