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Influencing the pozzolanic reaction of silica fume in a high-performance cementitious composite
Všetečka, Tomáš ; Šoukal, František (referee) ; Novotný, Radoslav (advisor)
This work deals with the effect of cement hydration and pozzolanic reaction of a high-perfomrance cement composite containing Portland cement and silica fume as binder. Concentrations of 0,5; 1,0; 2,0 and 4,0 wt.% of calcium ions to the binder were chosen to observe the effect. The selected compounds were calcium oxide (CaO), calcium hydroxide (Ca(OH)2), calcium formate (CF), calcium nitrate tetrahydrate (CN) and calcium chloride (CC). Calorimetric measurements showed that the optimum water to binder ratio was 0.4. Due to the lower workability, no high-performance cement composites were prepared but only pastes of high-performance cement composite. The effect of the added compounds on the silica fume-containing system was evaluated by isothermal calorimetry, with only samples containing CaO or Ca(OH)2 showing a measurable response. The effect of the added compounds on the silica fume containing system was evaluated by isothermal calorimetry. Subsequently, the effect of 4,0 wt.% Ca2+ in the CF, CN and CC forms on the system containing silica fume and 1,0 wt.% Ca2+ in the CaO or Ca(OH)2 form was evaluated using the R3 test. Isothermal calorimetry was also applied to paste samples containing cement and silica fume as a binder system, where a significant effect on the length of the induction period, on the value of the minimum heat flux in the induction period and on the value of the maximum heat flux in the main hydration peak was observed, especially for the compounds CF, CN and CC. The flexural tensile and compressive strengths of the paste samples were determined at 1, 3, 7 and 28 days after the start of hydration. The highest influence on the three-point bending tensile strength was again observed for compounds CF, CN and CC, with samples reaching significantly lower values than the reference (this was probably due to insufficient dissolution of the compounds). A lower influence on the flexural tensile strengths was observed for the oxide and calcium hydroxide samples. In the case of compressive strengths, there was a significant increase for CF, CN and CC compounds at 0,5 wt.% and 1,0 wt.% Ca2+ concentrations. In the thermal analysis and diffractometry results, a trend of loss of portlandite at the expense of CSH gel was observed for samples containing 4,0 wt.% Ca2+ in compounds CF, CN and CC. Thus, the added compounds probably influenced the kinetics of cement hydration so much that the silica fume had more time for pozzolanic reaction.
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Biodegradation of 3D printed composites based on poly(3-hydroxybutyrate)
Gazdová, Nikol ; Menčík, Přemysl (referee) ; Melčová, Veronika (advisor)
This bachelor thesis deals with the biodegradation of 3D printed bodies composed of poly(3- hyroxybutyrate), polylactic acid, bioceramics and plasticizer. These components were selected for their biocompatibility and properties that could be used in tissue engineering as a temporary, absorbable bone tissue replacement. The main objective was to investigate the effect of the individual constituent bodies on the biodegradation itself. Biodegradation was carried out at 37 °C in a solution simulating the ionic concentration of blood plasma. Samples were sequentially withdrawn at monthly intervals for five months. To evaluate the results, 2 methods were used, weight change and compression test, where the strength of each body was evaluated. From the evaluation of the data it was not possible to reach a uniform result on which substance influences biodegradation the most, because it always depended on the ratio of the other substances. To investigate the effect of poly(3-hydroxybutyrate) and polylactic acid on the rate of biodegradation, mixtures of RP9, RP10 and RP15 were compared. It showed that a higher polylactic acid and lower poly(3-hydroxybutyrate) content had a significant positive effect on the biodegradation rate, as the difference between the weight loss for the RP9 blend with the highest poly(3-hydroxybutyrate) content and the RP10 blend with the highest polylactic acid content was 8.37% for solid bodies and 4.13% for porous bodies. For strength, the difference was 73.32% and 73.65% for the solid and porous bodies, respectively. Observing the effect of bioceramic content on the RP11, RP12 and RP15 mixtures, we concluded that this effect was almost negligible on the biodegradation rate The difference in weight loss between the RP11 mixture with the lowest bioceramic content and the RP12 mixture with the highest bioceramic content was only 1, 68 % for solid bodies and 0.99 % for porous bodies, while mixture RP15 showed the highest biodegradation rate despite having a medium value of bioceramics in the mixture. For the mechanical properties, this then amounts to a difference of 10.4% for the solids and 7.57% for the porous bodies. When comparing the effect of plasticizer for mixes RP13, RP14 and RP15, the effect was more on the strength drop, where the difference in strength drop for mix RP13 with the lowest plasticizer content and RP14 with the highest plasticizer content was different by 20.3% and 18.16% for the solid and porous body, respectively. The decrease in weight was then different by 4.1 % and 0.83 % for the solid and porous body, respectively. Finally, bioceramics from different companies emerged as an important element for the biodegradation rate. Hydroxyapatite from Applichem was the best biodegraded and hydroxyapatite from CN Lab was the worst. The difference for weight loss was 17.35% for the solid and 5.93% for the porous body. The strength loss was then different by 55.6% for the solid body and 33.38% for the porous body.
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Application of Machine Learning for Prediction of Mechanical Properties of Mortars and Concretes
Prudil, Matěj
This paper deals with the application of machine learning (ML) in the field of concrete technology. Two databases of test mortars and concretes were created from selected academic theses, which include mechanical properties in relation to their composition. These databases were used to develop two ML models that predict the mechanical properties of mortars and concretes depending on their composition. The mortar test database contains a total of 242 mechanical property records and the concrete test database contains 111 records. The materials in the database are CEM I, CEM II and CEM III cements combined with additives such as ground granulated blast furnace slag, high temperature fly ash and micro-ground limestone.
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Utilization of waste glass in cement composites
Gottwaldová, Aneta ; Dufka, Amos (referee) ; Bodnárová, Lenka (advisor)
Bachelor thesis deals with the processing of waste glass in cement composites. Bachelor thesis includes a search theoretical and experimental part. Specifically, it was verified by fluorescent waste glass and glass screen at a dose of 5, 10, 15 and 20 weight % of a batch of cement. Properties of composites were examined after 7, 28, 56 and 90 days. We monitored TG analysis and XRD analysis of cement composites with waste glass.
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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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The utilization of the asphalt and concrete recycled materials to roads
Žďára, Zbyněk ; Šperka, Pavel (referee) ; Stehlík, Dušan (advisor)
This diploma thesis is divided into two parts, theoretical and practical. The is a review om the topic of recycled asphalt pavement and recycled concrete and their possible use in road construction in the theoretical part. The individual chapters deal with describing these materials, their production, and their use in construction layers of pavements. In the next chapters the attention is also paid to their problematic features and foreign experience using these materials in pavements. In the practical part, laboratory samples of recycled asphalt pavement and recycled concrete and their mixtures with cement are tested. The main purpose is to verify the applications of these mixtures of recycled asphalt pavement and recycled concrete in the bonded base layers of the pavement. Another purpose is to compare how these mixtures individual properties with different proportions of both components and different amounts of cement will be different. In the end, the two mixtures with the best properties was selected and the modulus of elasticity was experimentally determined for the possibility of replacing the currently used base layers and the economic evaluation of this design was made.
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The Influence of different Types of Fiber-reinforcement on the Behavior of Concrete Slabs
Wünsche, Dominik ; Žítt, Petr (referee) ; Kocáb, Dalibor (advisor)
The bachelor‘s thesis deals with the issue of concrete, specifically self-compacting concrete, fiber concrete and other types of concrete used. The work consists of two parts, the theoretical one, which will deal with the properties of the concrete. It describes the individual test methods used in the practical part. The test methods are the ultrasonic pulse method, the resonance method, the static modulus of elasticity, the compressive strength, and especially flexural strength. The second part is a practical part, which is processed by an experiment. In the experimental part, it will be mainly about carrying out tests of self-compacting concrete slabs and concrete with the addition of steel fibers. Subsequently, selected characteristics of concrete are determined and the whole experiment is evaluated.
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The development of high-strength concrete with a high content of el. fly ash
Roubal, David ; Ťažký, Tomáš (referee) ; Hela, Rudolf (advisor)
This diploma thesis deals with the study of high-strength, high-volume fly ash concrete. The theoretical part of this thesis focuses on the detailed characteristic and main principles of high-strength concrete, high-volume fly ash concrete. In addition, according to the findings, the technology of high-strength and high-volume fly ash concrete, including principles of high strength, has been described. On the basis of the findings, high-strength, high-volume fly ash concrete for specific compressive strengths has been designed and created in the experimental section. These concretes were then subjected to a number of tests.
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Comparison of selected parameters of tensile strength of concrete
Rozsypalová, Iva ; Žítt, Petr (referee) ; Daněk, Petr (advisor)
The thesis deals with a comparison of the selected strength tension properties of the hardened concrete and finding relationships between them. This is essentially a simple tensile strength, tensile flexural strength and tensile splitting strength. The text describe the testing procedures to determine the tensile strength of concrete. Furthermore, there are presented the results of testing on different types of concrete (plain concrete, lightweight concrete, steel-fiber concrete, polymer-fibre concrete and high strength concrete). The conclusion deals with the derivation of dependancy between concrete strengths and comparing the values obtained from the available relations with the results of the tests.
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