Dominik Gazdič

Slag-Sulphate Binder Preparation

Within the work the questions of the slag-sulphate binder preparation were solved. It was specifically a monitoring of obtained technological properties and course of the hydration process in dependence on dosing ratio of particular binder components. A finely ground Stramberk blast furnace slag was the basic raw material to which Polish natural anhydrite was added together with Portland cement CEM I 42,5 N as alkaline exciter.

Commercially Used Sulphate Binders Based on Anhydrite

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.

Method for the Accelerated Testing of the Durability of a Construction Binder using the Arrhenius Approach

Abstract 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.

Testing Self-Levelling Floor Screeds on the Basis of Ternary Binder

The work deals with processing and testing self-levelling floor screeds on the basis of ternary binder system of Portland cement - aluminous cement gypsum, to meet the target of ettringite development.

Monitoring of Calcium Sulphate Phase Transformations Using High-Temperature X-Ray Diffraction

Within the task the so called high-temperature X-ray diffraction analysis (HT-XRD) was used in the field of sulphated binders. Gypsum or calcium sulphate CaSO4.2H2O is the basic raw material for the sulphated binder production. As it is known by gradual warming of gypsum its different phase transformations can be obtained which significantly differ in its properties. Using this analysis identifications of temperatures of particular phase transformations in the CaSO4·xH2O system can be performed.

Possibilities of Alpha Gypsum Preparation in Chloride Salt Solutions

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.

Effect of the Milling Agents on Pozzolanic Activity of Glass

Currently the replacement of primary raw materials in cement production is relevant topic. One of the potentially usable materials can be recycled glass. But its disadvantage is tendency to agglomeration. This experiment describes the effects of the milling agents on the milling process of the glass powder. At first step seven different milling agents were compared among others and next the dependence between pozzolanic activity and specific surface are were monitored for two of them. The utilization of milling agents increased glass specific surface area significantly. Nevertheless, pozzolanic activity of the glass can be reduced when using milling agents because they may also act to a certain extent repellently to the reaction solution.

Synthetic Preparation and Properties of Ettringite

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.

Influence of Plasticizers on Properties of Anhydrite Binder

This paper deals with the development and research of sulphate binder based on anhydrite for the industrial production of dry mortar self-leveling mixtures. As part of the experimental activity, selected plasticizers for the sulphate binders were tested. These additives were added in various weight ranges. The tests were carried out first on anhydrite pastes and then on anhydrite mortars of standard composition. Their influence was mainly observed on the achieved basic technological properties, such as the consistency, the initial setting time and the achieved strength.

Influence of Ambient Temperature on Course of Cement Stone Solidification

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