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The study of the influence of selected temperature regime and potassium ions on the process of synthesis of belite (2CaO·SiO2, C2S) was carried out. The basic raw material was calcium carbonate (CaCO3) and amorphous silica (SiO2). The dosage of both components was based on the stoichiometric ratio of CaO:SiO2 in belite. The modification of the raw meal was carried out in the form of potash, K2O. Potash was dosed in the form of potassium carbonate, K2CO3, and potassium sulfate, K2SO4. The firing process was performed in a superkanthal furnace with two temperature modes, firing temperature: 1150 °C / 3 hours soaking and 1450 °C / 5 hours soaking. The evaluation performed by the experiment was based on mineralogical analysis by XRD analysis.

The stability of ettringite as high-watery mineral is highly dependent on the ambient temperature. Under standard laboratory conditions, onset of decomposition of this phase occurs at temperature of 80°C already and the theoretical temperature of the complete decomposition of ettringite is 180°C. Ettringite decomposition can occur at significantly different temperatures under humidity conditions other than the laboratory ones. Within the work verification of the possibility of synthetic preparation of ettringite by direct addition of aluminum sulfate, Al2(SO4)3·18H2O, and calcium hydroxide, Ca (OH)2, as an alternative method to the yeelimite hydration procedure was carried out. The stability of the resulting systems was examined in two different environments, namely in a laboratory environment and the environment of saturated water vapour. The phase composition of the samples was determined by X-ray diffraction (XRD) analysis, thermal analysis and scanning electron microscopy (SEM).

The aim of the work was to investigate the influence of extremely low and high temperature on the course of hydration of cement stone compared to the reference sample hydrated at normal conditions. The work was structured in such a way that Portland cement was first subjected to standard technological tests. Next, sets of test prisms using cement paste were prepared. This samples were immediately exposed to saturated water vapor in three temperature environments: 5 °C, 20 °C and 80 °C. The course of the hydration process during the first 28 days was monitored by the determination of the phase composition by XRD analysis and thermal analysis, and mediated by means of determination of tensile strength after bending and compressive strength. The low temperature did not have a negative effect on the final properties of the hardened cement stone. On the other hand, high temperature accelerated the initial phase of the hydration process, but negatively affected the resulting mechanical parameters

This paper deals with the verification of the possibility of preparing synthetic ettringite in a way of direct addition of aluminum sulfate and calcium hydroxide as an alternative to the hydration of yeelimite. The stability of the resulting system was studied using the X-ray diffraction (XRD) and differential thermal analysis (DTA) in two different environments, namely in a laboratory environment and the environment of saturated water vapour. The evaluations of X-ray diffraction analysis and thermal analysis show that in the ettringite sample stored in the laboratory environment, evaporation of molecular water and subsequent transformation of ettringite into metaettringite or monosulfate can occur over time. Conversely, exposition of saturated water vapour environment can lead to saturation of the system by free calcium ions due to the slow dissociation of calcium carbonate, and thereby increase the amount of ettringite at the expense of gypsum and aluminum amorphous phase. To verify the above, it is recommended long-term monitoring of samples exposed in monitored environments.

This study is focused on possibilities of utilization of fluidized combustion fly ash for manufacturing of fired hydraulic binders as one of the principal raw materials for production of binders close to traditional cements. As a basic raw material high-calcium limestone was used, which was subsequently mixed with fluidized combustion filter fly ash (FCFFA) and fluidized combustion bed fly ash (FCBFA). The selected value of the hydraulic module was 1.7. Total two two-component raw material mixture were prepared which were burnt in a laboratory furnace under conditions at temperature of 1200 °C and 1250 °C. The evaluation was done on the basis of mineralogical composition using X-Ray diffraction (XRD) analysis, determination of the chemical composition of clinker and achieved basic physical properties. The aim was to produce a binder which could be very similar to strongly hydraulic lime or to cements of lower strength classes.

The present work focuses on the use of fluid fly ash for Portland clinker burning. Fluid ashes are carriers of all basic oxides represented in the cement raw meal. However, while the share of hydraulic oxides is in ashes sufficient, there is a significant deficiency in calcium oxide content. Preliminary studies have shown that the combination thereof with calcite as the second essential component of the fluid fly-ashes for the raw material based on Portland clinker burning application, it is necessary to solve a problematic issues. The first one concerns the potential leakage SOx resulting from decomposition of CaSO4 ash into the atmosphere. The second circumstance is the correction tracks raw meal in order to redistribute in the samples prepared under the initial studies, the obtained clinker minerals content in favor of calcium silicate, of them further in favor of alite. The last issue is the evaluation of the impact of fluid utilization of fly ash as a partial raw material bases for reducing CO2 emissions in the Portland clinker burning.

Extensive research on sulphosilicate clinkers has been performed, primarily given by the ecological aspects. The formation of thaumasite and ettringite has become an important issue due to possible concrete deterioration, and also reducing greenhouse gas emissions. This work was aimed at hydration of ternesite based clinkers at low temperatures, with respect to thaumasite formation. Five clinkers with various compositions corresponding to stoichiometric ratios of elements in thaumasite and ternesite were prepared. Clinker-water suspensions were stored at 5 °C for up to 810 days. X-ray diffraction, DSC/TG, and SEM/EDS were used as the analytical tools. All the clinkers contained ternesite, belite, anhydrite, and free lime. As shown by the results, ternesite and belite preferably hydrate to CSH gels, and sulphate ions forming ternesite become a part of gypsum. The remaining portion of gypsum originated from anhydrite hydration. Gypsum reacted with silica and carbon dioxide to form thaumasite. Thaumasite was clearly identified already after 28 days of hydration, and for one sample, its content finally reached approximately 34 wt. %. It should be considered that the application of sulphoaluminate cements may possibly be connected with the sever risk of sulphate attack.

This article describes the results of experimental works, dealing with long-term observing of ettringite stability (Ca6Al2(SO4)3(OH)12·26H2O). Thermodynamic stability of this mineral is important in terms of potential use of fluidized bed combustion (FBC) ash as an additive to Portland cement. Within the experimental work it was carried out observing of the ettringite formation by hydration of yeelimitu (Ca4Al6(SO4)·O12) in laboratory conditions. For the preparation of yeelimite it was proposed a three-component raw material mixture, consisting of a high percent limestone and gypsum and corundum. This mixture was subsequently placed in platinum crucibles and burnt in superkanthal kiln at 1200 °C. Formed clinker was mixed in chosen ratio with water and it was prepared a set of testing samples. These samples were exposed in the laboratory environment for up to 180 days. The hydration of the clinker was carried out using X-ray diffraction analysis (XRD) by determining the mineralogical composition.

The work aims to study the behaviour of blended cement with fluidized filter ash (FFA) considering to formation of the increased proportion of ettringite and its eventual transformation into thaumasite. In part of an experiment there were prepared three cements, two of them served as a reference one-component and the reference blended cement with limestone, a third one was tested blended cement with a FFA. All three cements were put to determination of basic technological properties and next they were observed during hydration process.

The single most reliable indicator of a material’s durability is its performance in long-term tests, which cannot always be carried out due to a limited time budget. The second option is to perform some kind of accelerated durability tests. The aim of the work described in this article was to develop a method for the accelerated durability testing of binders. It was decided that the Arrhenius equation approach and the theory of chemical reaction kinetics would be applied in this case. The degradation process has been simplified to a single quantifiable parameter, which became compressive strength. A model hydraulic binder based on fluidised bed combustion ash (FBC ash) was chosen as the test subject for the development of the method. The model binder and its hydration products were tested by high-temperature X-ray diffraction analysis. The main hydration product of this binder was ettringite. Due to the thermodynamic instability of this mineral, it was possible to verify the proposed method via long term testing. In order to accelerate the chemical reactions in the binder, four combinations of two temperatures (65 and 85°C) and two different relative humidities (14 and 100%) were used. The upper temperature limit was chosen because of the results of the high-temperature x-ray testing of the ettringite’s decomposition. The calculation formulae for the accelerated durability tests were derived on the basis of data regarding the decrease in compressive strength under the conditions imposed by the four above-mentioned combinations. The mineralogical composition of the binder after degradation was also described. The final degradation product was gypsum under dry conditions and monosulphate under wet conditions. The validity of the method and formula was subsequently verified by means of long-term testing. A very good correspondence between the calculated and real values was achieved. The deviation of these values did not exceed 5 %. The designed and verified method does not also consider the influence of other effects, for instance, chemical corrosion or corrosion caused by frost-thaw cycles. However, this method could be a supplementary tool applicable to the study of degradation processes and the estimation of a binder´s durability as well. Jeden z nejspolehlivějších ukazatelů trvanlivosti materiálu jsou jeho vlastnosti v dlouhodobých testech, které ale nemohou být vždy provedeny kvůli časovému omezení. Druhou možností je provést zrychlené testy trvanlivosti. Cílem práce popsané v tomto článku bylo vyvinout metodu pro zrychlené testování trvanlivosti pojiv. Byl zvolen přístup založený na Arrheniově rovnici a teorii chemické reakční kinetiky.

Due to ecological overloading decrease, industrial by-products are utilized. Fly ash also belongs among these by-products. In Portland-composite cements, the high-temperature fly ash is applied nowadays, but fluidized bed combustion fly ash (FBC fly ash) is not used. The reason is that the FBC fly ash hydrates to form an undesirable ettringite, C 3 A . 3CaSO 4 . 32H 2 O. Decomposition temperature of ettringite in ambient conditions is most often mentioned in a range of 50 °C to 110 °C. In order to assess the ettringite long-term stability, ettringite was synthesized by hydration of mineral yeelimite, 3CaO . 3Al 2 O 3 . CaSO 4 . The aim of this paper is long-term observation of the hydration of yeelimite in environment of saturated water vapour and examination of how stable the products of hydration are under given conditions. Raw materials for preparation of yeelimite were gypsum, limestone and corundum, weighed according to stoichiometric ratio of yeelimite. The mixture was heated at temperature of 1200 °C, soak 3 hours. After quenching and grinding, yeelimite was hydrated with a water-yeelimite ratio of 0.3. The system was cured as pastes and stored in conditions at laboratory temperature and in settings of saturated water vapour (100% R.H.). In order to follow the progress of synthesis regularly, namely up to age of 180 days of hydration, X-ray diffraction (XRD) was chosen using diffractometer Empyrean PANalytical (CuK-alpha). Based on the XRD patterns, only minor part of ettringite was formed, whilst a majority of yeelimite was preserved. It has been found that ettringite was not the only one product of yeelimite hydration. From an age of 20 days of hydration, a small amount of monosulfate was identified, whose quantity rose gradually. Especially at later ages of hydration, transformation of ettringite into monosulfate was observed.

This work describes the crystallization and subsequent decomposition processes of ternesite when fired in an open air system. The effects of temperature and sintering period on phase composition and crystallinity were assessed post-mortem in samples fired in platinum crucibles in a laboratory furnace. High temperature XRD was used for observing phase and crystallinity changes in situ. The results indicate that the temperature of 1150 °C is neither high enough for a full synthesis of ternesite of sufficient quality nor high enough for its decomposition. It appears that the temperature of ternesite decomposition in an open system is around 1250 °C. The crystallites grow very fast at the beginning, until the size of 160 nm above which the grow rate is decreasing.

Currently ternesite, Ca5(SiO4)2SO4, is used in the cement production, is one of two key phases of calcium sulfoaluminate cement. Some investigators claim that this phase is nearly inert or very low reactive and it hydrates only after later age of hydration. In order to improve knowledge in this field, process of hydration of neat ternesite clinker under specific conditions of exposure was observed in this study. Ternesite was prepared by firing of raw meal consisting of high calcium limestone, microsilica and calcium sulfate hydrate. The resulting ternesite clinker was subsequently hydrated in four storage environments. Kinetics of hydration process was monitored in water and in environment of saturated carbonic acid, at two different temperatures of 5 and 40 °C. Mineralogical composition of hydrated samples was analyzed by X-Ray diffraction analysis (XRD) and by differential thermal analysis (DTA) in particular ages of hydration. Based on the results, it can be claimed that rate of decomposition of ternesite was related to conditions of storage. The rate of decomposition was significantly accelerated by the environment of carbonic acid and also by the elevated temperature. Presence of calcium carbonates in mineralogical forms of calcite, vaterite and aragonite, coupled with gypsum and thaumasite was identified. V současné době se používá ternesit, Ca5 (SiO4) 2S04, při výrobě cementu, je jeden ze dvou klíčové fáze cementu vápenatého sulfoaluminátu. Někteří výzkumníci tvrdí, že tato fáze je téměř inertní nebo velmi nízký reaktivní a hydratuje pouze po pozdějším věku hydratace. Za účelem zlepšení znalostí v této oblasti byl v této studii pozorován proces hydratace čistého tetranositového slinku za specifických podmínek expozice. Ternesit se připravil vypálením surové moučky skládající se z vápence s vysokým obsahem vápence, mikrosiliku a hydrátu síranu vápenatého. Výsledný ternesitový sliník byl následně hydratován ve čtyřech skladovacích prostředích. Kinetika hydratačního procesu byla monitorována ve vodě av prostředí nasycené kyseliny uhličité při dvou různých teplotách 5 a 40 ° C. Mineralogické složení hydratovaných vzorků bylo analyzováno rentgenovou difrakční analýzou (XRD) a diferenční tepelnou analýzou (DTA) v jednotlivých stádiích hydratace. Na základě výsledků lze tvrdit, že rychlost rozkladu ternesitu souvisí s podmínkami skladování. Rychlost rozkladu byla výrazně zrychlena okolním prostředím kyseliny uhličité a také zvýšenými teplotami. Byla zjištěna přítomnost uhličitanu vápenatého v mineralogických formách vápence, vaterite a aragonitu spolu se sádrou a thaumasitem.

The research work was focussed on grinding processes of beta gypsum using Pulverisette 6 planetary mill in order to obtain best technological properties. Sulphur binders originate by burnout of calcium sulphate dihydrate at different temperatures. All types are classified in air mortars therefore they can solidify, harden and remain stable only on air. Laboratory processed beta gypsum prepared from Pregips calcium sulphate characterised with high purity and relatively low moisture from Precheza a.s. Přerov chemical works was selected as basic material. The microstructure was monitored using MIRA 3 scanning electron microscope.

The goal of researching works was production of alpha hemihydrate of calcium sulphate by pressureless dehydration method in different solution of chloride salts at same molal concentration. Production was done in innovated dehydration device and main watched parameter was influence of dehydrating solutions based on KCl, NaCl and CaCl2 on properties of produced alpha plaster.

In the last years we have to think about the question of emission reduction. One of the biggest producer of these emission is industry, where the cement industry comes under it. The effort of cement-workers and other manufacturers of building materials is the reduction of harmful oxides in our air, including CO2, which is one of a group of unfavourable oxides.This paper deals with the study possibility of partial compensation limestone by FBC-ash. The expected effect is the reduction of CO2 emissions and saving limestone. Following the previous stage of the research a recipes were designed for Portland clinker burning limestone-based and FBC ash, it was carried out laboratory burning and on produced cements were made basic technological tests.

This paper deals with opportunity of FBC – ashes using for hydraulic binder preparation, and as one of the main material for preparation of binders closed to traditional cements. This way prepared binder should be closed to strong hydraulic limes potentially cements of lower strength classes.

Sulphur binders originate by burnout of calcium sulphate dihydrate at different temperatures. All types are classified in air mortars therefore they can solidify, harden and remain stable only on air.

Ashes from fluidized bed combustion, i.e. FBC ashes, are not being practically used for the production of hydraulic binders. The problem is their chemical and mineralogical composition. FBC ashes are characterized by a higher content of SO3, highly active free CaO and sometimes higher loss on ignition. The higher proportion of these substances has resulted in volume and temperature instability. However, FBC ashes could be used within a certain limit concentration in binders with relatively similar chemicalmineralogical composition such as Portland cement. The potential use of FBC ash for the preparation of blended Portland cements was studied in this paper. For this purpose, two types of FBC ashes and one type of traditional fly ash were selected. The first representative was a filter FBC ash, the second one was a bed FBC ash. Fly ash from pulverized coal combustion was used for comparison. The samples were prepared by co-grinding of the selected ash, Portland clinker and gypsum in a laboratory ball mill to a given value of specific surface area. Ash content was 15 % and 30 % of the total sample weight. The samples were subjected to the determination of basic technological properties -the water/cement ratio, setting times, strength, and soundness. The course of the hydration process was monitored by the qualitative method of X-ray diffraction analysis (XRD). The hydration product quantification was performed by the thermogravimetric analysis (TGA/DTA). The amount of CaO attributable to Ca(OH) 2 and CaCO3 was quantified. Based on the results, a conclusion was made that the utilization of FBC ash in blended Portland cement production is possible. The values of the physical-mechanical properties of the blended cements based on FBC ashes are similar to the reference. In the case of lower FBC ash content, they are even comparable with ordinary Portland cement. (C) 2017 The Authors. Published by Elsevier Ltd.

The article deals with preparation of Portland cements from raw material powder with reduced carbonated component. This component is replaced with fluidised fly ash. With prepared model cements tests of basic technological properties were carried out.

Currently, the binders of self-levelling mixtures are most commonly implemented as one-component or two-component (binary) systems. One-component systems are usually Portland cement or alumina cement alone, both further modified especially by plasticizers and dispersive additives. In addition to their indisputable advantages, one-component as well as binary systems have some drawbacks including worse technological properties in the case of one-component systems based on Portland cement and higher financial costs in the case of binary systems which are usually mixtures of anhydrite II and α-gypsum. These deficiencies should be addressed by a ternary system which represents a compromise between the quality and affordability of existing systems. The basis of this ternary system is Portland cement to which an expansion agent composed of alumina cement and gypsum or dry hydrate is added. In this system, it is expected that the required strength and volume stability will be provided by Portland cement and the expander, respectively. The aim of this work is to study the ternary binder system based on Portland cement, alumina cement and gypsum or supplementary non-traditional connective components for use in the industrial production of self-levelling mixtures.

This work is the opening chapter of the study that deals with products of degradation, which might form in hardened cement paste after exposure to sulphate attack. The article deals with ettringite preparation design and then with the realisation of this design

The purpose of research work has been to verify an influence of α-gypsum grinding on its final property. The production of α-gypsum was performed by pressureless method in salt solution with partial substitute still used dehydrating solution of sodium chloride and calcium chloride.

Presented article deals with burn of raw admixtures with low content of carbon component for Portland cement burn. Fluidized ash is used as substitution of carbon component. At burnt model cements there are tested basic technological properties and it is observed hydrating process.

The paper focuses on the study of the formation mechanism of belite (dicalcium silicate) catalyzed with potassium ions in the form of chemically pure salt of potassium sulphate at various modes of firing in order to increase its reactivity. To verify the function of potassium sulphate as a substance enhancing the reactivity of C2S, 3 material mixtures were tested; they contained 0, 1 and 2 % of K2O recalculated per fired dicalcium silicate.

The aim of the research was to find and test suitable plasticizing admixtures, which have result in reduction of high water coefficient, in order to improve final technological gypsum properties from waste sources of raw material.

Within the research at Institute of Technology of Building Materials and Components the questions of belite cement hydration speed improvement have been solved for a long time. In comparison with common Portland cements (alite type) these cements obtain almost identical final properties but the main shortage of them due to which they are not practically produced is their very low hydration process speed and thus insufficient initial strength for construction practice. A development of lower hydration heat is another difference of the belite cement from common Portland cements. In case of concreting of massive constructions as for example water dams this can be perceived as an important benefit, however in case of concreting during cold season of the year this appears as a definite negative. The belite cement also shows a lower inclination to concrete efflorescence and higher strength to aggressive environment due to lower CaO content. Both of the properties can be definitely understood as benefits compared to orthodox alite clinker. The raw material base of belite cements require less lime than production of common Portland cements and on that ground the implementation of its production would be a positive benefit for ecology in sense of CO2 emission reduction and also in improvement of economy of non-renewable raw material sources. The raw material is burnt to lower temperature than alite cement resulting in lower CO2 emission released in the atmosphere during the cement production. In addition at reduction of the temperature for more than 100 °C also heat consumption is reduced for 10 to 14 %, which has positive economical and ecological effects due to lower consumption of fuels. Within the research focussed on improvement of belite cement properties the study of hydration process course and technological properties of belite (C2S) prepared using low-energy burning modes was the aim of the research.

The task is solved in connection with Ministry of Industry and Trade project which is involved in development of a complex building programme based on high quality gypsum binder from secondary raw materials. Within one of sub-stages a solution of production of small plaster elements is subject of the project which should present a basic unit for construction of interior plaster partition walls. In the framework of the task a cast of plaster shaped block was carried out using a pilot form of own production. A plaster produced in optimised pilot way from the synthetic gypsum modified with plasticizer and retarding additive was used as a filler binder. After demoulding the produced block was exposed in laboratory environment and tested for setting of selected required properties according to standard EN 12859 (dimensions, density, flatness, tensile strength on bend, pH).

Due to the very gradual hydration of anhydrites and their very low strengths, modification of the properties of anhydrite by a suitable external exciter was resolved within the work. The experimental work was conducted on natural anhydride, and as possible exciters for hydration, the following products were selected and tested: water-free sodium sulphate; Portland cement CEM I 42,5 R; hydrated lime CL 90 Carmeuse. The dose of the exciter was consistent, i.e. 4.5 wt%. The affect on the increased speed of the hydrating process and the quality of the technological properties was monitored. The catalytic effect was evaluated by monitoring the course of the hydration process (using XRD analysis and thermo-gravimetric analysis) and also on the basis of the achieved technological properties.

The insufficient occurrence of raw material resources on our territory was one of the historical reasons for marginal production of sulphated binders from secondary raw-material resources. Also the unprofitability of material production based on calcium sulphate was related to this fact. This was changed in the end of the last century when formation of waste raw materials increased with industrial development. Secondary gypsums became basic raw material for production of plaster boards, plaster mixtures and anhydrite self-levelling mixtures. Wet flue gas cleaning desulphation process during which the energogypsum is formed is nowadays realised in major part of our power stations. Annual production of the energogypsum produced in this way in particular power stations is about 250 kt. The energogypsum is generally stored in stock piles as a so called stabilisate and partially is delivered to cement works as a solidification regulator. Chemogypsum is produced in chemical works where waste waters with content of SO42- occur, which must be desulphated with lime in water ambient. Further it is formed in citric acid productions where also sulphated waters occur. Last but no least it is also produced in industrial production of phosphates. Production of titanium dioxide is another example of the industry where the possibility of gypsum formation exists.

The necessity of continuously saving of natural resources and the continuously increasing utilization of waste materials, which results in by product of the primary production, is in the interest of sustainable life on the Earth. These valuable secondary raw materials are stored as waste and urge for use as inexpensive and easily available material. The Institute of Building Materials and Elements Technology at the Brno University of Technology, solves in the long term the problem of alpha gypsum preparation by dehydrating the gypsum in the solution of chloride salts. The gypsum dehydrates to alpha-hemi-hydrate by this method under atmospheric pressure in liquid environment. The tests were brought as far as to the stage of laboratory production. The chloride ions are after dehydration washed out and afterwards the gypsum is dried.

The work was devoted to the analysis of a commercially manufactured binder imported from Germany which is supposed to represent a natural anhydrite according to the accompanying documentation, industrially modified by hydration process activating agents. A similar analysis of the anhydrite binder commercially manufactured in Germany was carried out at the very beginning of investigation into the given problem. In the introductory study of applied research engaged in the feasibility of preparation of self-levelling mixes based on anhydrite binder, a specimen binder made by a German producer declared as a purely anhydrite binder, was analysed. However, it was found out by the analyses performed that this binder is a premium quality -gypsum according to all manifestations by a modified liquefying and retarding agent, possibly by other compounds. Due to potential changes that may have occurred since the initial study in the composition of the so-called anhydrite binders, exploration of composition of the binders currently used in the Czech Republic for preparation of self-levelling mixtures was carried out in this part of the experimental work. The exploration detected that the composition of the binding phase is the matter of know-how for the majority of companies, and as a result, the only one sample of binder has been obtained so far from the company which reserved their anonymity for this work.

In order to save limited natural resources by utilising industrial by-products, this paper focuses on an entirely new application of fluidized bed combustion fly ash (FBCFA) into Portland composite cements. It is not currently used because undesirable ettringite, 3CaO·Al2O3·3CaSO4·32H2O, is formed during the hydration of FBCFA. Although the stability of ettringite has been the subject of much research, the solution is not yet fully clear. Ettringite is generally considered to be stable up to a temperature of 110°C; however, some investigators claimed that ettringite may already decompose at even ambient temperatures. To prove these statements, ettringite was prepared by the hydration of ye’elimite, 3CaO·3Al2O3·CaSO4, and the system stored at laboratory temperature in two environments: in laboratory settings and in an environment of saturated water vapour. The mineralogical composition of ettringite was long term (up to 160 days of hydration) and was analysed by X-ray diffraction (XRD) and differential thermal analysis (DTA). The hydration of ye’elimite is a relatively complex process. Only approximately 30% of ettringite was formed under laboratory conditions that appeared to gradually convert into metaettringite. Within an environment of saturated water vapour, we observed the conversion of ettringite into monosulfate. Original ye’elimite was indicated as the dominant phase of both storages.

Brno University of Technology solves in the long term the problem of alpha gypsum preparation by dehydrating the gypsum in the solution of chloride salts. This study verified that alpha-gypsum can be trouble free prepared by gypsum dehydration in solution of a number chloride salts, among others CaCl2, MgCl2 or NaCl. In the same time it was found that owing to the different electro-chemical behavior of Potassium ions, the by heat conditioned reaction of gypsum with the KCl solution the dehydration doesn’t take place, but a partial substitution of Potassium ions by Calcium ions takes place. The product of this reaction is the mineral görgeyit, K2SO4.5CaSO4.H2O.This important problem was solved by reduction of the extremely electro-chemical high mobility of Potassium ions by the method of the mixed chloride solution with Potassium and Sodium ions, the mobility of which is in comparison with the preceding only one third. Samples of hemihydrate in the solution of mixed salts were prepared and tested in conclusion of the research.

Presented work is a part of an experiment where limestone is partially replaced by fluidized fly ash during cement manufacturing. Hydration of this type of cement is connected to formation of AFt phases – thaumasite and ettringite that cause serious damage to cement stone. Thaumasite (CaSiO3·CaCO3·CaSO4·15H2O) is less known and less common. It forms especially at lower temperatures. During its growth C-S-H phases are built into thaumasite unite cell, therefore, cement stone decomposes. To preclude thaumasite formation, further research of this mineral is necessary; therefore, its synthetic preparation in sufficient quality is important. The aim of this work was to verify several routes for thaumasite synthetic preparation. In the beginning, burning of mixtures prepared on stoichiometric proportions of compounds in thaumasite was done then two methods used in literature were tried and in the end a new method based on main calcium silicate phases was realized. Předkládaná práce je součástí experimentu kde se vápenec částečně nahrazuje fluidním popílkem při výrobě cementu. Hydratace tohoto druhu cementu vede k vzniku AFt fází – thaumasit a ettringit, které způsobují vážné škody na cementovém kameni. Thaumasite (CaSiO3· CaCO3· CaSO4·15H2O) je méně známý a méně častý.