Dana Koňáková

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.

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.

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.

Thermal Expansion of Aluminate Cement-Based Composite Containing Basalt Fibres with Different Length

This article is focused on thermal expansion of cement-based composite. Studied materials are concrete containing alumina cement, silica aggregates and they are reinforced by basalt fibres. Three different concrete varying in fibres length were prepared and its basic physical properties and thermal expansion were measured. Fibres lengths were 6mm and 12mm. Total amount of fibres in mixtures were constant, whereas the ratio of the fibers were changed. Results were compared with reference concrete with no fibres. It was proved positive effect of fibres on thermal expansion, when the lowest values of thermal strain were shown by material with just longer fibres.

The Comparison of Water, Water Vapour Transport Properties and Mechanical Characterization of Two Commercial Plasters on Market in the Czech Republic

This article deals with the comparison of two different renovation plasters produced by different companies in the Czech Republic. The selected stuccos were Feinputz 212 supplied by HASIT Šumavské vápenice a omítkárny s.r.o and Kbelosan F from Knauf Praha spol. s.r.o. They were studied in the means of basic physical properties, mechanical properties, water transport properties and water vapour transport properties. Results revealed only slight variations in bulk density, matrix density and open porosity, but in the means of transport properties, the plaster Feinputz 212 showed much higher openness to water and water vapour transport.

Influence of Moisture Content on the Thermal Properties of Concrete Containing Agricultural Waste Materials

This article deals with concrete containing waste material originating in a coir fibres extraction from outer protective peel of a coconut. Coir pith is used as cement replacement in amount of 5% and 10%. The influence of moisture content on the thermal properties of studied concrete is determined by means of experimental measurements of basic physical properties, hygric transport parameters and thermal characteristics. From achieved results it can be concluded, that the higher amount of coir pith is used, the better values of thermal characteristics material show. But at the same time thermal characteristics are more influenced by moisture content.