Vliv dlouhodobého působení přírodmích podmínek na hydrofóbní vlastnosti povrchových vrstev

Ing. Radka Navrátilová, Ph.D.

In this paper water transport and storage parameters of hydrophobic plasters are studies. This article is focused on behavior of water and its degradation process inside of material matrix. Most of physic-chemical deteriorations of building materials are related to the penetration of moisture into building structure. For higher resistance of penetration water into materials, hydrophobic additions are used. Especially inner hydrophobic additive was applied to the interior structure to reduce destructive effect of water. Water storage parameters are slightly better for plaster without hydrophobisation. However, from the quantitative point of view the difference was not so important. Comparative measurements with pure lime-metakaolin plaster were done as well.

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Ing. Radka Navrátilová, Ph.D.

The effect of hydrophobic agent on rheological properties of modified plasters is analyzed in this paper. Influence of time and external temperature (10, 20 and 30°C) on samples is examined. Main aim of rheological test is determination of flow curves, obtained by applying a succession of constant strain rates for short times. On the basis of the experiments performed, it can be concluded that the both time and temperature have very significant influence on rheological properties same as hydrophobic addition. A comparative measurement with pure metakaolin-lime plaster was done as well.

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Ing. Radka Navrátilová, Ph.D.

Článek shrnuje vliv vylučovaného vodíku a dihydrátu bis(trihydroxozinečnatanu) vápenatého (Ca[Zn(OH)3]2·2H2O) na vývoj pórovité struktury cementového tmelu v okolí žárově zinkované oceli. Tyto látky vznikají katodickou (vodík) a anodickou (zinečnatany-vzniklé reakcí s hydroxidy) korozní reakcí žárově zinkované oceli (nebo čistého zinku) v cementovém tmelu. Pórová struktura cementového tmelu byla sledována rtuťovou porozimetrií, analýzou obrazu prostřednictvím rastrovací elektronové mikroskopie a konfokální mikroskopií. Vlivem koroze žárově zinkované oceli za vývoje vodíku dochází ke zvýšení pórovitosti cementového tmelu na fázovém rozhraní žárově zinkovaná ocel/tmel. Tato porézní struktura je zachována po celou dobu zrání cementového tmelu. Kinetika koroze zinkované oceli souvisí prioritně s transportem vody tmelem. Uvedený zinečnatan vápenatý není schopen samostatně zajistit přechod koroze zinkované oceli z aktivního do pasivního stavu.

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Ing. Radka Navrátilová, Ph.D.

The article deals with the corrosive effects of acids on the selected surface layers of concrete with/ without an epoxy coating. Concrete sample was placed in extreme environments, which represented the 40% sulphuric acid solution. In addition to measuring surface degradation of concrete, this work focused on the depth of acid penetration into the sample. It can be concluded that the long-term effects of aggressive environments severely degrades the concrete surface on the samples causing corrosion of Type II.

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Ing. Radka Navrátilová, Ph.D.

In this paper water storage parameters of hydrophobic plasters are determined. This article is focus on hygric properties of lime-metakaolin plaster connected with hydrophobicity. Most physic-chemical deterioration of building materials related to the penetration of moisture into building structure. Therefore, the aim of the testing was in description of influence of inner hydrophobic additive, which was applied to the interior structure of the element. Higher resistance of penetration water into materials show samples with hydrophobic additive. Water storage parameters are slightly better for plaster without hydrophobsation. However from the quantitative point of view the difference was not so important. Measurement involves not only properties of hydrophobic plaster, but comparative measurements with pure lime-metakaolin plaster were done as well.

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Ing. Radka Navrátilová, Ph.D.

Influence of hydrophobic additives on resistance to alkali environment is described in this paper. This article is focus on surface properties of vibropressed concrete connected with hydrophobicity. The aim of the testing was in description of influence of several types of hydrophobic additives, which were applied either to the interior structure or either as a coating on the surface of the element. In some cases, it was a combination of both. The article is about specific measurement of resistance against alkalis. Higher resistance to alkali and therefore better durability properties show samples with hydrophobic coating than with inner additives. All the samples with inner impregnation exceeded its permitted limits established for the alkali resistance multi-times. Measurement involves not only resistance to alkalis but also tests of frost resistance and water absorption depending on time.

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Ing. Radka Navrátilová, Ph.D.

The review of hydrophobic materials application on surfaces of concrete structures to achieve its protection again the environmental conditions is described in this paper. The article is focused on the characteristics of selected hydrophobic materials, chemical base of origin and their characteristics. The second part describes the possibility of experimental methods of measuring of new hydrophobic surface layer, particularly the quality and efficiency of their hydrophobic properties.

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Ing. Radka Navrátilová, Ph.D.

In this paper open porosity as a function of hydrophobic properties was examined. It was measured three kinds of porous building materials which differ in their structure and properties. Especially, concrete samples such as: aerated concrete (denote as AC), normal strength concrete (denote as NSC) and ultra high performance concrete (denote as UHPC). We were focused on measurement of open porosity and distribution of pores in structure by microscopic method. The result clearly shows that concrete samples differ in among of pores, its geometric shape and deep and mainly in its distributions.

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Ing. Radka Navrátilová, Ph.D.

The effect of hydrophobic agent admixture on water vapour and liquid water transport properties of newly designed lime plasters is analysed in the paper. The major part of physico - chemical building deterioration is related to the penetration of moisture and soluble salts into the building structure. For that reason, the modified lime plasters were in the broad range of basic material properties tested. From the quantitative point of view, the measured results clearly demonstrate the big differences in the behaviour of studied materials depending on applied modifying admixtures. From the practical point of view, plaster made of lime hydrate, metakaolin, zinc stearate and air-entraining agent can be recommended for renovation purposes. The accessed material parameters will be used as input data for computational modelling of moisture transport in this type of porous building materials and will be stored in material database.

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Ing. Radka Navrátilová, Ph.D.

Lime plasters are the most popular finishing materials in renewal of historical buildings and culture monuments. Because of their limited durability, new materials and design solutions are investigated in order to improve plasters performance in harmful environmental conditions. For the practical use, the plasters mechanical resistivity and the compatibility with substrate are the most decisive material parameters. However, also plasters hygric and thermal parameters affecting the overall hygrothermal function of the renovated structures are of the particular importance. On this account, the effect of moisture content on the thermophysical properties of a newly designed lime plasters containing hydrophobic admixture is analysed in the paper. For the comparative purposes, the reference lime and cement-lime plasters are tested as well. Basic characterization of the tested materials is done using bulk density, matrix density, and porosity measurements. Thermal conductivity and volumetric heat capacity in the broad range of moisture content are experimentally accessed using a transient impulse method. The obtained data reveals the significant increase of the both studied thermal parameters with increasing moisture content and gives information on plasters behaviour in a highly humid environment and/or in the case of their possible direct contact with liquid water. The accessed material parameters will be stored in a material database, where can find use as an input data for computational modelling of coupled heat and moisture transport in this type of porous building materials.

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Ing. Veronika Steinerová, Ing. Radka Navrátilová, Ph.D.

Cílem uvedeného článku je způsobem srozumitelným nejen pro úzce specializovanou, ale i širší odbornou veřejnost dostatečně přesně objasnit problematiku koroze žárově zinkované výztuže v betonu.

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Ing. Veronika Steinerová, Ing. Radka Navrátilová, Ph.D.

Cílem uvedeného článku je způsobem srozumitelným nejen pro úzce specializovanou, ale i širší odbornou veřejnost dostatečně přesně objasnit problematiku koroze žárově zinkované výztuže v betonu. Je zde poměrně detailně zhodnocen dřívější pozitivní náhled na využitelnost žárově zinkované výztuže se zohledněním koroze a především soudržnosti s betonem.

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Ing. Radka Navrátilová, Ph.D.

In this paper is described principle of hydrophobicity as a function method for increases durability and service life of building materials. Several types of hydrophobic additives, which were applied either to the interior structure or either as a coating on the surface of the element, were tested. In some cases, it was a combination of both. The article is about specific measurement of resistance against alkalis. Higher resistance to alkali and therefore better durability properties show samples with hydrophobic coating than with inner additives. All the samples with inner impregnation exceeded its permitted limits established for the alkali resistance multi-times, i.e. result is in terms of resistance significantly negative.

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Ing. Radka Navrátilová, Ph.D.

Influence of different type of hydrophobic additives on the concrete elements is presented in this paper. The aim of the article is experimental analysis of susceptibility to the formation of efflorescence depending on type of hydrophobic additive and its application. Hydrophobicity is obtained by coatings and internal additives. Measurement involves not only qualitative and quantitative efflorescence test but also determination of chemical composition of leaching salt crystals and also sorption properties. From the results obtained follows that the different kind of hydrophobic additive as well as type of its application have impact on the concrete surface properties.

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Ing. Radka Navrátilová, Ph.D.

Influence of different type of hydrophobic additives on the concrete elements is presented in this paper. The aim of the article is experimental analysis of susceptibility to the formation of efflorescence depending on type of hydrophobic additive and its application. Hydrophobicity is obtained by coatings and internal additives. Measurement involves not only qualitative and quantitative efflorescence test but also determination of chemical composition of leaching salt crystals and also sorption properties. From the results obtained follows that the different kind of hydrophobic additive as well as type of its application have impact on the concrete surface properties

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Ing. Radka Navrátilová, Ph.D.

The effect of metakaolin and hydrophobic agent admixture on properties of newly designed lime plasters is analysed in the paper. The overall majority of physical - chemical building deterioration is related to the penetration of moisture and soluble salts into the building structure. For that reason, the modified lime plasters were in the wide range of various properties tested. Comparative measurement declared the usage of metakaolin and zinc stearate does not significantly influenced basic physical parameters and water vapour transport, but reduced the liquid water transport which is very positive finding.

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Ing. Radka Navrátilová, Ph.D.

In a previous study, we presented new method measurement rheological properties of hydrophobized plaster in dependence of hardening time. Influence of external temperature on pozzolana plaster is analyzed in this paper, especially plasticity and workability of paste. Main aim of rheological test is determination of flow curves, obtained by applying a succession of constant strain rates for short times at the temperature 10°C and 30°C. Base on the performed experiments, it can be concluded that the temperature have very significant influence on rheological properties of plasters. With an increase in temperature, the application time of the mixture is shorter, from hour to minutes. A comparative measurement with pure lime plaster was done as well.

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Ing. Radka Navrátilová, Ph.D.

The influence of time on rheological properties of modified lime plaster is analyzed in this paper. Effect of composition of mixture is examined as well. Especially changes of paste due to hydrophobic and pozzolanic admixture. Main aim of rheological test is determination of flow curves, obtained by applying a succession of constant strain rates for short times. Base on performed experiments, it can be concluded that hydrophobic admixture eliminated influence of pozzolana. Also both time and temperature caused significant changes in rheological properties. Increasing values decreases the flow characteristic of the plaster. A comparative measurement with pure lime plaster was done as well.

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Ing. Radka Navrátilová, Ph.D.

The review of hydrophobic materials application on surfaces of concrete structures to achieve its protection again the environmental conditions is described in this paper. The article is focused on the characteristics of selected hydrophobic materials, chemical base of origin and their characteristics. The second part describes the possibility of experimental methods of measuring of new hydrophobic surface layer, particularly the quality and efficiency of their hydrophobic properties.

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HSC (High Strength Concrete) is increasingly used for bearing bridge structures nowadays. Bridge structures in the Czech Republic are exposed to severe conditions in winter time and durability of the concrete is therefore a crucial requirement. The high strength and low water absorption of HSC suggests that the material will have high durability. However, the situation may not be so straightforward. We carried out a study of the very poor durability of HSC concrete C70/85 used to produce prestresed beams 37.1 m in length to build a 6-span highway bridge. After the beams were cast, a production control test indicated some problems with the durability of the concrete. There was a danger that 42 of the beams would not be suitable for use. All participants in the bridge project finally decided, after extensive discussions, to attempt to improve the durability of the concrete by applying a hydrophobic agent. Paper will present the results of comparative tests of four hydrophobic agents in order to choose one for real application and describes this application on construction site.

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