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Possibilities of using tailings from the ore mining for the production of blended cements.
Šrámek, Ondřej ; Gazdič, Dominik (referee) ; Dvořák, Karel (advisor)
The bachelor's thesis deals with the possibility of partial replacement of Portland clinker in blended cements. It is focused on the study of the slate’s usability, especially their calcination ability and the analysis of the activatability of pozzolanic properties by a suitable temperature. A search of the available literature was performed in this work. Also suitable type of sedimentary slate was selected, on which a basic experiments was performed. The experiments showed that slate has enough minerals with the potential of pozzolanic properties and this was proved at a calcination temperature above 600 °C.
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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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Lime Mortars Modified by Fine Ground Brick Body
Šmerdová, Ludmila ; Vyšvařil, Martin (referee) ; Rovnaníková, Pavla (advisor)
Natural pozzolanic materials played an important role in Ancient architecture. In the last decades and nowadays it is artifical pozzolan which especially finds its use as an additive to mortar and concrete to improve some, especially the mechanical properties. This master thesis deals with study of pozzolan type of fine brick powder which is a by-product of the production of calibrated bricks. Along with studying pozzolanic activity of brick powder, lime mortar with different proportions of brick powder as an additive or replacement of lime dust are investigated. What is observed is its impact on the consistency of these mortar, water absorption, strength in time or fracture-mechanical parameters of mortar. The results may indicate the possible potential use of this source of pozzolanic admixture in lime mortar and plaster which are nowadays mainly used for the restoration of facades of historic buildings.
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Pozzolanic Activity of Silicon Dioxide
Barek, Jaroslav ; Žižková, Nikol (referee) ; Rovnaníková, Pavla (advisor)
The aim of this bachelor's thesis is to investigate and identify the present status of resources with dominant amorphous silicon dioxide content and summarize feasible test methods to assess pozzolanic activity. The use of pozzolan as a partial replacement of Portland cement reduces the carbon dioxide emitted per tonne of product and can also improve various physical properties of the resulting cementitious composites. Assessment of the pozzolanic activity of cement replacement materials is increasingly important because of the economic sustainability of cementing materials. The pozzolanic activity of wheat straw ash, silica fume, nanosilica, two diatomites, glass powder and expanded perlite have been investigated and compared using the strength activity index test, the modified Chapelle test and the pozzolanicity test in accordance with the European Standard EN 196-5. From an experimental investigation of seven different pozzolans, the following main conclusions can be drawn. In the case of an acid-base titration (determination of [OH–], the procedure specified in EN 196-5) is better to use Tashiro (mixed indicator) instead of required methyl orange, Tashiro changes color at the endpoint of a titration distinctly. Strength activity index: the procedure used was based on EN 450-1. In its current form, this procedure is misleading because of two other significant properties of the pozzolan, namely its density and its water-reducing/increasing capabilities. Based on the results of our experimental investigation, the current testing procedure is evaluated against an alternative in which the 25% pozzolan replacement for cement is performed on a volumetric basis and the volume fraction of water is held constant.
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Investigation and Modelling of Concrete Carbonation
Rovnaníková, Markéta ; Keršner, Zbyněk (referee) ; Bajza, Adolf (referee) ; Havlica, Jaromír (advisor)
The corrosion of steel reinforcement is probably the most frequent type of degradation of reinforced concrete structures. Reinforcing bars are protected from corrosion by a thin iron oxide layer which is formed on their surface due to a high alkalinity of the surrounding concrete. Corrosion may start when this layer is destroyed (i) either by chloride ion penetration (when the concentration of dissolved chloride at the depth of the reinforcing steel exceeds a critical value) or (ii) by a reduction in the pH value of pore solution to values below 9.5. Such a reduction in alkalinity is the result of carbonation of the Ca(OH)2 in the concrete mass, i.e. of its reaction with the atmospheric CO2. The main aim of this work is an experimental investigation and modelling of carbonation process. The effect of relative humidity, curing period and replacement of Portland cement by supplementary cementing materials (SCM - fly ash, blast furnace slag and metakaolin) on carbonation process has been studied. Calcium hydroxide content in the presence of SCM and their pozzolanic activities have been also determined. Furthermore, lots of parametric studies and comparison of carbonation models have been provided. The software tools based on the introduced models and considering the input data to be statistically independent random variables have been described and used for other parametric studies.
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Plasters modified by burnt clays
Soukupová, Eva ; Příhoda,, Jiří (referee) ; Sokolář, Radomír (referee) ; Michoinová,, Dagmar (referee) ; Rovnaníková, Pavla (advisor)
The doctoral thesis deals with the reactivity of burnt clays in connection with modified lime mortars. The theoretical part of the doctoral thesis provides an overview of the properties of lime mortars, their quality and ways of their degradation. The different types of burnt clays (brick powder, bentonites and burnt clay shale), their origin, properties and factors affecting their reactivity and methods of its evaluation are stated. The properties and reactivity of burnt clays are evaluated on the basis of determination of pozzolanic activity, mineralogical and chemical composition, surface area, density, content of the amorphous phase and granulometry in the experimental part of the doctoral thesis. The compositions of lime mortars containing burnt clays and evaluation of an impact of burnt clay on the properties of mortars in the fresh and hardened state are given. Consistency, bulk density, workability and air content of mortars in the fresh state are evaluated. Strength characteristics depending on the time, water absorbability, porosity, capillary attraction, adhesion, coefficient of diffusion resistance, frost resistance, shrinkage, mineralogical composition and microstructure of mortars in the hardened state are evaluated. Attention is also paid to the influence of the cellulose ether addition into the modified lime mortars.
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