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Study of the possibilities of using superabsorbent additives in concrete
Kubíček, Matyáš ; Jančář,, Josef (referee) ; Hela, Rudolf (advisor)
This bachelor's thesis deals with the study of self-healing of cracks in cement composites. In the theoretical part, four chapters describe the mechanisms that influence the durability of concrete or can extend it. In the first chapter, I deal with concrete additives that affect the water consumption in concrete. This chapter is focused on plasticizers. In the second chapter, I deal with the treatment of concrete, how long to treat it and what are the ways of treating it. In the third chapter, I write about rehabilitation, about the additional life extension of building structures using various technologies and mechanisms. The fourth and last chapter of the theoretical part is the most comprehensive and discusses the self-healing mechanisms of concrete with the help of several types of microorganisms that heal cracks with their products. Then about calcium lactates, which are often combined with microorganisms to improve the effects of self-healing. About non-metallic polymer fibers, both natural and synthetically produced, added to concrete to improve properties. In the last subsections, I mention the use of colloidal SiO2 solutions and especially superabsorbent polymers, the investigation of which plays a significant role in this thesis. In the experimental part, the influence of the amount of superabsorbent additive in concrete on the ability of self-healing is investigated. The ability to heal cracks, which will be artificially created after mixing the concrete mixture, when placing the concrete in the forms, is investigated. Furthermore, the influence of the effect of the superabsorbent additive in different deposits will be investigated. Subsequently, the samples will be tested for tensile strength after bending and compressive strength.
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Verification of ECPC and EPCC concepts for the use of the k-value of selected active admixtures with mixed cement
Prudil, Matěj ; Slánský,, Bohuslav (referee) ; Hela, Rudolf (advisor)
This bachelor thesis deals with the verification of the replacement of blended cement, latent hydraulic and pozzolanic additions used in the production of concrete. In the theoretical part of this thesis, the use of blended cements in concrete production is firstly described and the effect of additions on the properties of fresh and hardened concrete is briefly discussed. The next chapters focus on fly ash and blast furnace slag as Type II additions and their basic properties. The theoretical part also focuses exclusively on the concepts used to replace cement with active additions. These concepts are successively presented in this thesis as: K-value concept, Equivalent concrete performance concept (ECPC) and Equivalent performance of combinations concept (EPCC). In the experimental part, the properties of the test mortars with cement replacement by concrete active additions (slag from Kotouč Štramberk and high temperature fly ash from Opatovice and Chvaletice) are compared. The above mentioned concepts for the replacement of cement with active additions are evaluated in the experimental part from the economic point of view (prices per m3 of concrete) and ecological point of view (calculation of carbon footprint in t CO2 per m3 of concrete production). In order to compare these benefits, a concrete mix of strength class C30/37 is proposed according to each concept. From the knowledge gained in the development of the ECPC and EPCC concepts, a q-value concept is proposed in the experimental part. In the last chapter of the experimental part, the resulting values of this work are compared with the experimental work already carried out to replace Portland cement with identical active admixtures.
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Effect of Cement on the K-Value of Power Plant Fly Ash
Šperling, Petr ; Hela, Rudolf
This paper deals with the determination of the k-value and activity index for power plant fly ash with CEM I 42.5 R cement and CEM II/A-M (S-V) 42.5 R cement. The objective is to determine the activity index of this active admixture for different cement replacements to determine the k-value based on the relationship between water coefficient and compressive strength for fly ash and to assess the effect of different cement types on the kvalue. Based on the results obtained, the effect of blended cement, which has a higher amount of active admixture than Portland cement, on the compressive strength, the activity index and the k-value of fly ash was assessed.
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Verification of the Applicability of Mixed Cement Types for the Production of Concrete Pavements
Klobása, Jan ; Hela, Rudolf
Concrete is the most widely used building material today. Due to the increase in the utility value of buildings, more and more emphasis is placed on the durability of buildings, which especially applies to concrete products exposed to frost and chemical deicing agents. Cement concrete pavements have the ability to transmit the effects of traffic and withstand adverse weather conditions. Concrete pavements can withstand high traffic loads without permanent deformations and have a long service life. However, it must be said that in the case of damage to the CB pavements, repairs require longer closures due to more demanding production and laying technology. The expected lifespan of a concrete road type is at least 30 years with basic and minimal maintenance, while the life cycle of tarmac roads is much shorter.
Currently, great importance is placed on reducing emissions arising from industrial production, especially cement production, where it is stated that the production of 1 ton of cement produces approximately 0.6 tons of CO2. Reducing emissions is possible thanks to secondary raw materials that are produced in large volumes in the Czech Republic, for which a suitable use is being sought.
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Development of concrete with high fly ash content and verification of durability in various environments
Ambruz, Pavel ; Voves, Jiří (referee) ; Hela, Rudolf (advisor)
This thesis contains two main parts: theoretical and experimental. The theoretical part deals with summarization knowledge of high-volume fly ash (HVFA) concretes. Among others, there are mentioned processes of producing of fly ash, characteristic features and resistance to aggressive environments of HVFA concretes. The theoretical part ends with a suitable example of practical application. In the practical part were tested properties of nine different mixtures containing 40%, 50% and 60% replacement by weight of the cement by fly ash. They were compared with the reference mixtures without fly ash addition. The main endpoints were long-term compressive strength, resistance to aggressive environments, the influence of fly ash on consistency, hydratation temperatures, water absorption and volume changes.
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Reactive Powder Concrete
Gabko, Miroslav ; Klečka,, Tomáš (referee) ; Hela, Rudolf (advisor)
Reactive powder composites (RPC) have been recently a subject of many researches of modern concrete technology. This type of concrete is very fine and its behaviour exceeds the other types of concrete, therefore there are new possibilities of its use. The design and production of RPC is complex technology process which needs to gain new results in RPC research to get the best features regarding its higher price. This thesis is focused on design of reactive powder concrete (RPC200), which compressive strength is between 200 – 300 MPa. Next goal is to prove the influence of curing regimes like high temperature or pressure, and also check the possibilities of production of low cement reactive powder composite (LCRPC).
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The influence of crystallization additives to waterproof concrete
Rosecký, Pavel ; Louda, Pavel (referee) ; Hela, Rudolf (advisor)
This bachelor´s thesis deals with influence of crystallization additives to waterproof concrete. In the theoretical part is detailed analysis individual components in concrete production, improving waterproofing properties and finally functions and properties of crystallization materials. In the practical part I deal with influence of selected crystallization additives on properties of fresh and hardened concrete.
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Development of concrete with limited volume changes
Martanová, Jana ; Skopal, Ing Karel (referee) ; Hela, Rudolf (advisor)
The bachelor thesis deals with volume changes of concrete. Attention is paid to the shrinkage. They describe the different kinds of volume changes in cement concrete, the reason for their creation and the ways in which they can be eliminated. The practical part is focused on monitoring the volume changes of concrete for 28 days using different amount of plasticing additives.
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