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Influence of variations in cement composition on bleeding and mortar workability over time
Peřina, Tomáš ; Klečka,, Tomáš (referee) ; Hela, Rudolf (advisor)
This diploma thesis is divided into two parts, the theoretical and practical part. The theoretical part is to study of factors influencing the workability and bleeding of concrete. There is mentioned the production of cement and standard requirement. The task of the practical part is to assess the cements produced by the cement works Hranice and Prachovice. These cements test in terms of water separation. In combination with these cements use superplasticizing admixtures from Mapei and Stachema and determine the impact of water separation on cement pastes. Determine rheology on the cement pastes. Define influence of variations in cement composition affect the stability of cement mixtures.
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Reological properties of cement pastes modified by amorphous SiO2
Zimmermann, Štěpán ; Rovnaník, Pavel (referee) ; Vyšvařil, Martin (advisor)
The subject of this thesis are the rheological properties of cement paste with the addition of amorphous silicon dioxide. The basic rheological parameters are that describe the behavior of cement pastes in the fresh state. The work also included rheological tests including measurement principle and method of evaluation. Effect of mineral admixtures with high content of amorphous SiO2 is summarized the available scientific articles. In the experimental part, the effects of impurities with a high content of amorphous SiO2 on the rheological properties of fresh cement paste. It was tested by substitution of up to 10 % by weight of cement in the cement pastes mineral admixtures of different chemical composition, particle size and pozzolanic activity. Flow measurement was measured yield value, viscosity, and flow index. The stability of cement pastes was investigated oscillatory measurements. To complement the behavior pastes in the fresh state was determined by calorimetry. Test results were compared with those determined by reference samples and compared the effect of various ingredients.
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Study of alkali metals ions diffusion in hardened cement
Doležal, Martin ; Janča, Martin (referee) ; Šoukal, František (advisor)
This master thesis is aim to study alkali diffusion (sodium, potassium) in hardened cement paste body. It´s deal with impact of various sorroudings (hydroxide, nitrate and carbonate) in various concentrations and temperature effect. This work is also deal with changes in cement paste and medium. Teoretic part is talking about cement production and cement chemistry, alkali-silica reaction, plasticizer, diffusion an cement testing metods. This work is aimed to white (Aalborg CEM I 52,5 R – SR 5) and road (Mokrá CEM I 42,5 R – sc) cement. Experimental part describes constitution of tested cement pastes, conservation of them and sampling. Diffusion is study by ICP-AES which affected the loss of alkali from the solution and SEM which affected alkali migration (diffusion) in cement paste. In several cases, the formation of a saturated alkali edge was observed, followed by steady diffusion. In the case of potassium there was very slow diffusion through the body mass. The influence of medium and temperature was evaluated as the most significant. The effect of medium concentration wasn´t significant. Also changes in the porosity on the body were observed. The diffusion itself was affected by secondary products gorwing on the surface of body and in the medium. The work deals with them in the last part.
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: Development of special high strength concrete with low volume changes
Meruňka, Milan ; Hela,, Vlastimil (referee) ; Hela, Rudolf (advisor)
The bachelor thesis deals with problems of volume changes of concrete, especially shrinkage of concrete. Types of concrete changes, causes, occurrences, and ways to eliminate them are described. The experimental part is focused on monitoring the volume changes of concrete within 28 days of maturing using a different type and dose of shrinkage reducing additions, a summary of cement pastes within 24 hours of mixing, the development of temperatures of the hydration temperatures of concrete and cement pastes.
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Influence of hydration accelerators on zinc - doped cement mortars
Beneš, Pavel ; Šilerová, Iva (referee) ; Šiler, Pavel (advisor)
This work deals with monitoring the hydration of cement mortars and cement pastes made from CEM I 42.5 R cement doped with zinc oxide in an amount of 1 % wt. To eliminate the delay in the onset of hydration due to the presence of zinc oxide, the following accelerators were added to the cement mixtures in different proportions: calcium oxide, formic acids and calcium formate. Hydration was monitored using isoperibolic calorimetry. Furthermore, the mechanical properties of mixtures were investigated, namely the tensile strength after bending and the compressive strength after 7 days and after 28 days. The cement mortars were further subjected to additional analyses, such as porosimetry, DTA/TG and SEM.
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Study of alkali metals ions diffusion in hardened cement
Doležal, Martin ; Janča, Martin (referee) ; Šoukal, František (advisor)
This master thesis is aim to study alkali diffusion (sodium, potassium) in hardened cement paste body. It´s deal with impact of various sorroudings (hydroxide, nitrate and carbonate) in various concentrations and temperature effect. This work is also deal with changes in cement paste and medium. Teoretic part is talking about cement production and cement chemistry, alkali-silica reaction, plasticizer, diffusion an cement testing metods. This work is aimed to white (Aalborg CEM I 52,5 R – SR 5) and road (Mokrá CEM I 42,5 R – sc) cement. Experimental part describes constitution of tested cement pastes, conservation of them and sampling. Diffusion is study by ICP-AES which affected the loss of alkali from the solution and SEM which affected alkali migration (diffusion) in cement paste. In several cases, the formation of a saturated alkali edge was observed, followed by steady diffusion. In the case of potassium there was very slow diffusion through the body mass. The influence of medium and temperature was evaluated as the most significant. The effect of medium concentration wasn´t significant. Also changes in the porosity on the body were observed. The diffusion itself was affected by secondary products gorwing on the surface of body and in the medium. The work deals with them in the last part.
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|
Influence of variations in cement composition on bleeding and mortar workability over time
Peřina, Tomáš ; Klečka,, Tomáš (referee) ; Hela, Rudolf (advisor)
This diploma thesis is divided into two parts, the theoretical and practical part. The theoretical part is to study of factors influencing the workability and bleeding of concrete. There is mentioned the production of cement and standard requirement. The task of the practical part is to assess the cements produced by the cement works Hranice and Prachovice. These cements test in terms of water separation. In combination with these cements use superplasticizing admixtures from Mapei and Stachema and determine the impact of water separation on cement pastes. Determine rheology on the cement pastes. Define influence of variations in cement composition affect the stability of cement mixtures.
|
|
|
: Development of special high strength concrete with low volume changes
Meruňka, Milan ; Hela,, Vlastimil (referee) ; Hela, Rudolf (advisor)
The bachelor thesis deals with problems of volume changes of concrete, especially shrinkage of concrete. Types of concrete changes, causes, occurrences, and ways to eliminate them are described. The experimental part is focused on monitoring the volume changes of concrete within 28 days of maturing using a different type and dose of shrinkage reducing additions, a summary of cement pastes within 24 hours of mixing, the development of temperatures of the hydration temperatures of concrete and cement pastes.
|
|
|
Reological properties of cement pastes modified by amorphous SiO2
Zimmermann, Štěpán ; Rovnaník, Pavel (referee) ; Vyšvařil, Martin (advisor)
The subject of this thesis are the rheological properties of cement paste with the addition of amorphous silicon dioxide. The basic rheological parameters are that describe the behavior of cement pastes in the fresh state. The work also included rheological tests including measurement principle and method of evaluation. Effect of mineral admixtures with high content of amorphous SiO2 is summarized the available scientific articles. In the experimental part, the effects of impurities with a high content of amorphous SiO2 on the rheological properties of fresh cement paste. It was tested by substitution of up to 10 % by weight of cement in the cement pastes mineral admixtures of different chemical composition, particle size and pozzolanic activity. Flow measurement was measured yield value, viscosity, and flow index. The stability of cement pastes was investigated oscillatory measurements. To complement the behavior pastes in the fresh state was determined by calorimetry. Test results were compared with those determined by reference samples and compared the effect of various ingredients.
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