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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Nové možnosti využití lehčených kameniv z druhotných surovin / Development od flooring systems with usage od lightweight aggregate

Jankovský, Jiří January 2012 (has links)
The work deals with the possibilities of lightening of the flooring system. Flooring system is solved by lightening the material. The surface layer is modified by lightweight fillers made from the waste materials, lightweight waste materials and fillers made from natural substances. Simultaneously is this work dealing with options of lightening the surface layer by microspheric fillers of separated waste fly ash.
22

Studium závislostí složení betonů na hodnoty modulů pružnosti / Study of the dependence of concrete composition on the values of elasticity modules

Křížová, Klára January 2013 (has links)
The modulus of elasticity is one of the basic characteristics of concrete defining elastic deformation of concrete and it plays a significant role in the static design of structures. Due to current trends in concrete technology, offering a wide variability in the proposals of the composition of concrete, there are changes not only in strength characteristics but also in the modulus of elasticity of concrete. The aim of this doctoral thesis is to study the dependence of different compositions on modulus of elasticity of concrete. Design of concrete composition is prepared with respect to the use of different types of cement, mineral admixtures, types and fractions of aggregates. The work is mainly focused on the determination of static modulus of elasticity in compression with the addition of dynamic modules. In the first phase determined modulus of elasticity are compared with tabulated values according to Eurocode 2, which are derived for the specific strength class of concrete. Part of this work is the compilation of the main technological aspects of concrete which can favorably affect the modulus of elasticity.
23

Konstrukční vlastnosti ultralehkých betonů a jeho optimální využití v konstrukcích / Structural Properties of Ultralight Concrete and its Optimal Application in Structures

Kadlec, Jaroslav January 2017 (has links)
This doctoral thesis deals with design of three variants of ultra lightweight concrete (ULC) and their mechanical properties. The ULC usually has the dry density of 900-1200 kg/m3 and it is possible to use it for load bearing structures. Low density of ULC is achieved by replacing heavy aggregate for lightweight aggregate. The lightweight aggregate is known under the trade name Liapor in the Czech Republic. To achieve density below 1000 kg/m3, an aeration of the paste has to be done. An exchange of heavy aggregate for lightweight aggregate results in a very fragile behavior of ULC. A great attention is paid to bond strength between concrete and reinforcing steel in the thesis. In addition to the standard test of bond strength testing by pull-out, a modified pull-out test is designed, which includes the effect of minimum reinforcement cover. The mentioned test more precisely simulates a real behaviour of the structure exposed to bending moment. The doctoral thesis tries to point out on different parameters between measured data and the applicable standard for the design of load-bearing structures.
24

Využití těženého kameniva do podkladních vrstev vozovek / The usage of the quarried aggregates to base layers of pavements

Borkesz, Michael January 2017 (has links)
The work deals with the possibilities of using fine crushed and quarried aggregate to base layers of roads. The introduction of the theoretical part explains the origin of this type of aggregate. There are also described the tests, which were used to verify the attributes and features of these mixtures and their use in cemented base layers of roads. In a brief way, the work also deals with foreign research and the possibilities that arise from it. In the practical part is then described the process of mixture preparing and laboratory tests carried out on them, the production of test specimens, load tests of these specimens and interpretation of the results. The conclusion summarizes the findings. Here are also discussed ways to apply them in practice.
25

Vliv složení a mikrostruktury vulkanických hornin na jejich technologické vlastnosti / Influence of composition and fabric of volcanic rocks on their technological properties

Krutilová, Kateřina January 2015 (has links)
Because of a very variable geological composition of the Czech Republic, there is a various scale of all genetic types of rocks that are used for the production of crushed stone. The most often used group of rocks are effusive magmatic rocks, which represent about 34 % of crushed stone marketed (Starý et al. 2010). These rocks are used for all kinds of construction purposes including roads. The experimental material of crushed stone used in this thesis was sampled from 40 active quarries in the Czech Republic. The studied volcanic rocks originated from Neoproterozoic and Paleozoic complexes of Barrandien, Carboniferous and Permian of Krkonose Piedmont Basin, Carboniferous and Permian of Intrasudetic basin, area of ordovician Železné Hory, from the main volcanic center of Bohemian Massif in the north-west Bohemia (České středohoří Mts. and Doupov Mts.), Neovolcanic area of Czech Cretaceous basin and area of Neovolcanic East and West Sudeten. Petrographic study was carried out in a form of standard petrographic analysis of thin sections and chemical analysis, which helped inclusion of rocks to a classified systems. The whole suite of volcanic rocks was separated to five petrographic-technologic subgroups defined as: (1) rhyolites / porphyres, (2) phonolites, (3) basalts s.l., (4) spilites and (5)...
26

Studium tepelně izolačních vlastností cementových betonů při zvýšené teplotě / Study of thermal insulation properties of cement concrete exposed to high temperature

Nováková, Iveta January 2014 (has links)
Master`s thesis is divided in to two parts, practical and theoretical. In theoretical part are listed basic information’s about light weight concrete, special emphasis are given to characteristic and practical application of compact light weight concrete with Liapor aggregates. In this study is described influence of high temperature on concrete structure and chemical, mechanical and physical changes, which take place during exposal to high temperatures. Further is evaluated surface permeability of concrete and addition of polypropylene fibres to concretes resistive to high temperatures. The practical part deals with design, production and testing of cement based concrete with use of different aggregates (light weight aggregates Liapor, basalt). The properties and use for applications in high temperatures is also mentioned. The influence of high temperature on strength, absorption, thermal conductivity, changes of surface permeability and degradation of testing specimens due to heat loads according to normative heat curve (ISO 834). For better transparency are experimental tests divided in to five phases and the measured values are evaluated on the end of each phase. In conclusion are resumed all knowledge’s obtained by testing and evaluated the most suitable formulation. The approach for further research is also mentioned.
27

Studium chování betonů při působení vysokých teplot / Studying the behavior of concrete at high temperatures

Fiala, Jiří January 2015 (has links)
This thesis deals with the behavior of cement concrete at high temperature with a focus on the impact behavior of aggregate, cement type and polypropylene fiber reinforcement. The theoretical part describes the issue of cement concrete at high temperatures, especially processes in the cement matrix, aggregates and polypropylene fibers. Furthermore, theoretical part describes the selection of a suitable type of cement and aggregates in concrete exposed to high temperatures. In the experimental part was designed the concrete composition with various kinds different types of aggregates and two types of cements. The temperature stress of test samples was performed according to ISO standard temperature curve 834. Subsequently, was made the verification of the physic-mechanical properties such as changes in bulk density and compressive strength after heat load. Moreover, the surface appearance of samples after heat load was evaluated, especially the occurrence of samples, the crack width and explosive spalling. Mineralogical composition changes of prepared samples before and after heat load were observed via X-ray diffraction analysis. Finally, we made a photogrammetry on a test plates after heat load which defined the size of the area and depth of spalling concrete surface.
28

Lehké malty s obsahem alternativních surovin odolné působení nepříznivých vlivů / Lightweight mortars with content of alternative raw materials and resistant to adverse effects

Morkusová, Kristýna January 2018 (has links)
This diploma thesis describes research and following development of lightweight cement mortars with alternative raw materials. Attention was focused on study of the effects of extreme influences such as high temperature (up to 1200 °C), freeze-thaw and agressive sulfur dioxide. Verification of durability of developed mortars was realized using physical and mechanical tests (density and strength), physical and chemical methods (computed tomography) and scanning electron microscopy. Assessment of durability was realized in a longer period of time (90 days).
29

Ultralehké betony s vysokými užitnými vlastnostmi / Ultralight concrete with high utility properties

Popelková, Adéla January 2018 (has links)
This diploma thesis deals with the technology of production of ultralight concretes using direct lighten cementing compound and at the same time indirect lighten using lightweight aggregate. Further work deals with the choice of suitable raw materials for these concretes. The practical part consists of a proposal of several different recipes, experimental verification and by comparing their properties in a fresh or hardened state.
30

Využití umělého spékaného kameniva vyráběného z pevných energetických odpadů do betonu / THE USE OF SINTERED ARTIFICIAL AGGREGATES PRODUCED FROM SOLID ENERGETIC WASTE FOR CONCRETE.

Batelka, Michal Unknown Date (has links)
This work deals with issues aimed at the possibility of treating the material which has not been used yet – coal tailings. The work includes among others the production, its optimalization and utilization of a new type of lightweight artificial aggregate in the process of production of concrete. The possibility of manufactured the artificial aggregate is dealt with the principle of self-burning of the raw material's batch at the agglomerative grate. The optimalization of the burning process was performed both with the homogenous and the layered batch. Further part of the work focuses on the fabrication of diverse types of concrete and determination of their parametres. This section is significantly extended with the comparison of basic physical and specific properities of the new type of concrete with those of the commonly produced types. The last part of presented work deals with the ecological - economic situation of these issues. The proposed solution points to the possibility of utilization of the coal tailings which are put to the tailings heaps. It was managed to optimize the burning process and to find the most convenient system for storing the raw material's batch at the agglomerative grate. Next, it was proved that the types of concrete produced with a new sort of aggregate are also suitable for fabricating the construction concrete with the strength above the border of 50 MPa, which are applicable even in harder conditions. These sorts of concrete also have a lower volume weight and very good bending properties. The major finding, which underlines the contribution of this work, is that the up to now unused material is suitable for fabrication of relatively high-quality and thermally stable aggregate of strength on the border of 5 MPa, which can be use for fabricating concrete with very good results even in this field. Another great contribution of this work can surely be the fact, that a preliminary economic balance of the manufacturing pr

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