Eva Vejmelková

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.

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.

Characterization of Building Stones Involved in Historical Masonry

Basic physical properties, pore size distribution and hygric properties of several types of stones which are used in reconstructions of historical buildings on the territory of the Czech Republic, namely several types of sandstone and argillite, are investigated. Basic physical characteristics are measured using the water vacuum saturation method, pore distribution by mercury porosimetry. Values of water absorption coefficient and apparent moisture diffusivity are determined by methods utilizing the results of water sorptivity measurements. Water vapor transport properties are accessed by the cup method. The obtained data represents valuable information for the application of studied materials in reconstructions and renewal of historical buildings.

Mechanical, hygric and thermal properties of building stones

Basic physical properties, pore distribution, mechanical, hygric, and thermal properties of several types of building stones which were used in historical buildings on the Czech territory in medieval times, namely several types of sandstone and argillite, are investigated. Bulk density, matrix density and open porosity are measured using the water vacuum saturation method, pore distribution by mercury porosimetry, compressive and bending strength by a hydraulic testing device. Apparent moisture diffusivity is determined by utilizing the results of water sorptivity measurements, the dependence of moisture diffusivity on moisture content is obtained by measuring moisture profiles using a capacitance technique and subsequent solution of the inverse problem of moisture diffusion. Water vapor diffusion permeability is measured by the cup method, sorption isotherms are determined by the desiccator method. Thermal conductivity and specific heat capacity are measured by an impulse technique in the moisture range from the dry state to full water saturation.

Thermal Properties of PVA-Fiber Reinforced Cement Composites at High Temperatures

Properties of polyvinyl alcohol-fiber reinforced cement composites are investigated as functions of temperature up to 1000 °C. Basic physical properties are measured using the water vacuum saturation method. High-temperature thermal diffusivity is determined by a transient method based on the analysis of temperature field at one-sided sample heating. High-temperature specific heat capacity is obtained using a non-adiabatic method. Experimental results show that the studied material exhibits a satisfactory resistance to high-temperature exposure and has a potential for using in high-temperature applications in building industry.

Innovative Lime-Pozzolana Renders for Reconstruction of Historical Buildings

Bulk density, matrix density, open porosity, compressive strength, bending strength, water sorptivity, moisture diffusivity, water vapor diffusion coefficient, thermal conductivity, specific heat capacity and thermal diffusivity of two innovative renovation renders on limepozzolana basis are analyzed. The obtained results are compared with reference lime plaster and two commercial renovation renders, and conclusions on the applicability of the particular renders in practical reconstruction works are drawn.

Pore System and Hydric Properties of Two Different Lime Plasters with Finely Crushed Brick

Two different lime plasters with finely crushed brick are studied in this article. In the first plaster the pozzolan mixture was used as silica sand while in the second it was dosed as replacement of the lime substitute and silica sand (the substitution levels being 20% and 50%). Classic lime plaster was used as a reference material. Studied parameters were basic physical properties (measured by water vacuum saturation and by helium pycnometry), characterization of pore system (by mercury porosimetry) and transport of liquid water.

Basic Physical and Mechanical Properties of Composites Based on Three Different Cements

This article is focused on cement based composites. Two cements differing in mineralogical composition are utilised as main binder in composites mixtures. Results of measured physical parameters of studied materials are presented. For the sake of comparison, a reference material with Portland cement was also prepared. Basic physical properties (measured by water vacuum saturation method and by helium pycnometry), characterizations of pore system (determined by mercury porosimetry) and mechanical properties are the matter of this study. Composites show various open porosity; the results of open porosity of materials containing special cements show higher values, in comparison with composite based on Portland cement. This fact of course influences other material characteristics - mainly mechanical properties.

Hygric Properties of HPC with Natural Pozzolana

The water vapour transport and the liquid water transport of high performance concrete (HPC) with the content of natural pozzolana are the described in this paper. Studied properties are presented by means of water vapour diffusion coefficient, water vapour diffusion resistance factor and absorption coefficient respectively. The natural pozzolana (NP), namely natural zeolite, is used as supplementary cementitious material which affects the durability properties of the end product. The obtained results revealed the effectiveness of NP in the terms of both studied properties when used in small amounts, i.e. at about 20% of cement weight. On the other hand substitutions higher than 40% result in worsening of the resistance of the concrete to water and water vapour ingress and its movement trough the material.

Comparison of the Effects of Different Pozzolana on the Properties of Self-Compacting Concrete

The article compares the basic physical, mechanical and both liquid water and water vapour transport properties of self-compacting concrete containing different pozzolanic admixtures. Limestone, fly ash and metakaolin were used. A concrete mixture without any pozzolana was also manufactured as a reference. The best values of studied properties were recorded for the metakaolin concrete.