|
|
Effect of plasticizers on the behaviour and properties of alkali activated materials
Langová, Markéta ; Koplík, Jan (referee) ; Kalina, Lukáš (advisor)
Alkali activated materials could be suitable alternative to construction materials based on ordinary Portland cement (OPC). Therefore, it is advisable to pursue these binders further on. Aim of this thesis is to clarify the effect of lignosulfonate-based plasticizer and polycarboxylate-based superplasticizer on the behaviour and nature of alkali activated materials. For the purposes of studying the efficiency of plasticizing additives, the change of workability of alkali activated blast furnace slag in dependence on time, effect of additives on mechanical properties as well as, with usage of isothermal calorimetry, their impact on kinetics of solidification and hardening had been observed. The stability of the plasticizing admixtures in a high alkaline environment such as water glass and sodium hydroxide had been studied using infrared spectrometry. As a last step, X-ray photoelectron spectroscopy (XPS) had been used while clarifying the chemical changes in the structure of plasticizing additives after adsorption to blast furnace slag.
|
|
|
Study of shrinkage reducing admixture efficiency in alkali activated systems
Fojtík, Ondřej ; Koplík, Jan (referee) ; Bílek, Vlastimil (advisor)
Significant drying shrinkage is one of the major issues for the wider application of materials based on alkali-activated slag (AAS). Some shrinkage reducing admixtures (SRA) were developed for the ordinary portland cement systems. A couple of previous studies focused on the efficiency of these SRA in alkali-activated materials. The studies were mainly concentrated on the SRA based on polypropylene glycol. This thesis deals with efficiency of the SRA based on 2 methyl-2,4-pentanediol in AAS pastes and mortars. Influence of the SRA and activator (waterglass) dose on the drying shrinkage and other properties of AAS (flexural and compressive strength, autogenous shrinkage, workability, setting time and microstructure) were investigated. It was found, that at the activator dose when Na2O/slag mass ratio equals 4 or 6 %, SRA causes retardation of hydration, which leads to shrinkage reduction, however strength is reduced significantly, weight lost during the drying is increased and the coarsening of the pore structure occurs. At the activator dose when Na2O/slag mass ratio reaches 8, 10 or 12 %, in the presence of SRA the drying shrinkage is reduced, weight lost during the drying is similar to the reference, strength is increased and microstructure is unchanged against reference. It has been proved that SRA works properly in AAS only at higher activator doses.
|
|
|
Influence of inorganic admixtures on shrinkage reduction of alkali activated materials
Šístková, Pavlína ; Koplík, Jan (referee) ; Kalina, Lukáš (advisor)
This bachelor thesis is focused on the influence of inorganic admixtures on shrinkage reduction of alkali activated materials. In the theoretical part the issue of alkali activated materials is explained in detail focusing on the reduction of their shrinkage. Alkali activated system is constituted by alkali activated blast furnace slag. Firstly, the effect of inorganic dashes is monitored such as low calcium fly ash and finely ground limestone. Furthermore, the influence of inorganic additives for reducing shrinkage has been studied, namely magnesium oxide and calcium oxide. The aim of this work is to determinate the mechanical properties and shrinkage of individual alkali activated mixture and then discuss whether there was a reduction of shrinkage and what the effect of added dashes and inorganic admixtures was.
|
|
|
Leachability of Cu, Ni and Co from alkali-activated matrices
Janíčková, Vlasta ; Kalina, Lukáš (referee) ; Koplík, Jan (advisor)
The work deals with the determination and comparison of leaching of heavy metals from two types of alkali activated systems based on blast furnace slag and high-temperature fly ash. These systems are capable in their structure encapsulate heavy metals, toxic substances or radioactive substances, which can be harmful for the environment. The aim of this work is to prepare a mixture with acceptable mechanical properties. Leachibility from matrix was tested according to ČSN EN 12457–4, followed by analyses Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Structure of matrix was analysed using Scanning electron microscope (SEM).
|
|
|
Advanced ceramics for tissue engineering
Vojtíšek, Jan ; Koplík, Jan (referee) ; Bartoníčková, Eva (advisor)
This bachelor´s thesis deals issues of ceramics materials suitable for tissue engineering. An artificial substitute for human tissue can be divided to several generations. This include inert, bioactive and bioresobable materials. Resorbable substitutions are prepared from materials, which could substitute host tissue, for example hydroxyapatite. HA can be prepared in different ways (dry and wet way). To better application in medicine, ceramics foams prepared by in situ foaming or replication technique are using. Experimental part of this paper deals preparing of hydroxyapatite powder and process optimization. Samples was characterized by IR and Raman spectrometry, XRD analysis and particle size was studied by SEM. Ceramics foams was prepared by in situ foaming from Al2O3, HA and composites (in ratio 50 – 50, 75 – 25, 90 – 10). Porosity was evaluated by stereomicroscope, density and level of sintering was studied by SEM microscopy.
|
|
|
The binder based on the high-calcium ash - the influence of the alkali activator
Šichnárek, Vojtěch ; Kotrla, Jan (referee) ; Koplík, Jan (advisor)
The aim of this thesis was examination of the influence of different alkali activators to final properties of binders based on fluidized bed combustion fly ash. There were prepared mixtures containing sodium waterglass or sodium carbonate. Curing time, consistence, and strengths after 2, 7, 14 and 28 days were measured. X-ray diffraction and X-ray fluorescence were used to find out the composition of samples. There were taken images and element spectra using scanning electron microscope and isothermal calorimetry was used to determine the heat flow during the time of curing. The results indicate that the use of water glass achieves better initial workability and pressure strengths are higher than besides sodium carbonate. However, when sodium carbonate is used, pressure strengths are lower, but they are less dependent on the amount of the activator and do not change as much with time. Crystallographic composition is dependent to the activator used – by using sodium waterglass there was more of ettringite and portlandite in the sample.
|
|
|
The influence of different anions on fixation of Cu in alkali-activated blast furnace slag
Böhm, Petr ; Kotrla, Jan (referee) ; Koplík, Jan (advisor)
The work deals with the fixation of copper in alkali activated blast furnace slag and with the influence of anionts (sulphate, nitrate, chloride and oxide) to its immobilization. This is tested according to leaching tests ČSN EN – 12457 4. The concentration of copper in leachates was determined by inductively coupled plasma optical emission spectrometry. The aim of this work is to check the influence of addition (copper) to the resulting mechanical properties and also specify, how the heavy metal is bonded in the matrix. The structure was examined by scanning electron microscopy.
|
|
|
Calcium aluminate hydrates - laboratory preparation and characterisation
Koplík, Jan ; Opravil, Tomáš (referee) ; Šoukal, František (advisor)
Calcium aluminate phases are important parts of Ordinary Portland cement and Alumina cement. Various calcium aluminate hydrates originate during the hydration of calcium alumina phases. Their origin depends on the conditions of hydration. In the diploma thesis was investigated hydration of four calcium aluminate phases – CA, CA2, C12A7, C3A under the conditions of four pH – 6, 9, 11, 12,65. Calcium aluminate phases were prepared from CaCO3 and Al2O3 by clinkering in solid phase in laboratory oven. The phases were hydrated for 48 hours. Kinetics of the hydration was investigated by calorimetry. Calcium aluminate hydrates were identified by XRD and DTA.
|
|
|
Semiconducting ceramics for thermoelectric application
Jebavá, Alžběta ; Koplík, Jan (referee) ; Bartoníčková, Eva (advisor)
This diploma thesis focuses on the syhnthesis of multicomponent ceramic system based on Ca-(Mn,Co)-O. The thesis is devided in theoretical and experimental part. The theoretical part is describing ceramic materials for thermoelectric application, preparation and synthesis of these materials and their processing. The experimental part is dealing with synthesis of ceramic powder which is processed to the porous ceramics. The properties of prepared porous ceramics are observed.
|
|
|
Combined aluminium-silicon based sol-gel binding system for refractory
Taraba, Vojtěch ; Koplík, Jan (referee) ; Švec, Jiří (advisor)
The following piece of work deals with the use of a combined aluminium-silicon based sol-gel binding system for refractory. The effect of different gelling agents on the gelation process was observed and rheometric measurements were performed for MgO. After optimizating the drying process, the resulting gel was characterized by thermal analyses, based on which the firing temperatures were selected. Qualitative analysis of the gels fired to the selected temperatures was performed using FTIR. Using XRD, the semi-quantitative phase composition of the samples was monitored as a function of firing temperature. The topography of the test bodies prepared based on results of the previous analyses was later observed using a scanning electron microscope.
|
guest ::
RSS feed.