Dušan Dolák

Effect of the Firing Process to the Lime Crystallinity

This work is focused on the effect and properties of input material on speed of decarbonation. Various types of limestones were used from quarries all around the world and their different properties and behavior were studied. The aim of this research is to find the influence of chemical composition, petrography, porosity and microstructure of limestones on speed .and profile of decarbonation. Process of decarbonation of calcite is subsequently evaluated for the crystallinity of the newly formed product.

The Relation of Limestone Origin and its Reactivity to the Preparation of Desulphurization Agents

Limestone is used in the flue gas desulphurization process due to its ability to form sulfur compounds. Different qualities of limestone absorbents can be used in the process and it is therefore important to measure the reactivity of these materials. A limestone with a 90 to 95% of calcium carbonate is used to prepare limestone slurry for the flue gas desulphurization. It is very important to explore the different properties of the raw material for a better understanding of the desulphurization process and also the impact on the economic aspect of the process [1-3]. This article presents a study about limestones reactivity, which is measured by the Bischof-Uhde method. At first the study monitors the impact of the milling of set of Czech limestones on their reactivity and furthermore deals with the influence of the genesis and porosity of the set of world limestones also on the reactivity of limestones in the desulphurization process.

Testing and Optimization of Production of Technical Foam for the Production of Cement Foam

In the current construction industry, great importance is given to the usage of thermally insulating building materials. One of the many such materials can be a cement foam or foam concrete, a mixture of cement mortar and technical foam. This material can be, due to its consistency right after mixing, applied to uneven horizontal surfaces where usage of conventional thermal board insulation materials would be complicated. This paper discusses the methodology of testing of the physical and mechanical properties of foaming additives such as strength, density, foaming number and half-separability of technical foams. Then this methodology was subsequently verified on the five commonly used foaming additives in the Czech Republic.

Comparison of Mineralogical Changes during Thermal Processing of Limestones

Thermal treatment of materials involves phase transformations. In the case of conventional laboratory furnace or in an industrial process, the samples are analysed after cooling. In this way, these phases can be monitored. A possible solution is non-ambient XRD analysis. Using HT-XRD analysis, it is possible to monitor the mineralogical composition at different temperatures in real time. The results of measurements on chemically precipitated limestone and limestone from the Cretaceous era show slight differences in temperature of decarbonation, but not clearly demonstrated the presence of unstable phases. This measurement, however, allowed the observation of a change in the size of the crystallites in the change of temperature.

Effect of Firing Temperature on Reactivity and Sedimentation Volume of Different Types of Limestones

Limestone as a natural rock tends to have various parameters. Variation in parameters, as well as firing temperature have significant impact on key properties of quicklime. Sedimentation volume and reactivity determine quality of quicklime in building industry. This paper is focused on monitoring the reactivity and sedimentation volume of quicklime prepared from various types of limestone at different temperatures. Selection of limestones with high purity collected from various quarries around the world were characterized by porosity, chemical and petrographic composition. To create quicklime, these samples were fired at 4 different temperatures. Reactivity measurements were made on quicklime with specific particle size. Sedimentation volume of hydrated slurry was determined. Obtained results suggest that there is tendency for slower reactivity and smaller sedimentation volume with increased firing temperature.

Alternative Evaluation of the grindability of Pozzolanic Materials for Cement Production

An ecological way of reducing CO2 emissions in cement production is the usage of blended cement with an active pozzolan. A part of this issue is the adjustment of granularity of raw materials. This is often achieved by the grinding of the input components. All conventional methods for the evaluation of grindability require a specific grinding instrument. These grinding instruments do not have any other practical use and thus are not very common. This paper focuses on the alternative evaluation of grindability. Inspired by the VTI method used in the coal industry, which uses porcelain laboratory ball mill and compares material based of oversize particles, a new method was created. The first modification in methodology was the use of a planetary mill instead of a porcelain drum mill. Another modification was in the measurement of undersize by means of laser granulometry. This method was then tested on clinker, slag, and recycled glass, which can also be used as an active pozzolan in blended cement. Also, co-milling measurements were made on clinker-pozzolan combinations. These results were then used in the calculation of the grindability index, which can be used for the comparison of properties. The modification of the VTI methodology has a positive impact on the evaluation of grindability, especially with regard to fine particles, thanks to the use of laser granulometry and at the same time it makes use of more a commonly available grinding apparatus

Impact of Plasticizers on Technological Properties of Gypsum

Sulphate binders based on gypsum are widely used in building industry. This research work was focused on testing the influence of Melflux plasticizers on the final properties of the gypsum mixture. The aim was to determine the correct concentration of the plasticizer considering workability and improvement of mechanical properties, especially the compressive strength. Different concentrations of plasticizers were tested in mixture of alfa and beta plaster. Each batch was created as paste of normal consistency to create accurate comparison. The results of experiment show significant improvements of mechanical strength of the hardened mixture while maintaining same consistency. This knowledge can be utilized in the design of high-strength sulphate binders.

Initial Analysis for Study of Pure Limestone Decarbonation

Over the past 70 years dozens of works that deal with the relationship between the properties of limestone, burning modes and properties of lime were created. The expected properties of lime should be proportionate to the nature and burning technology of limestone. But very often the reality is different. General relationships and dependencies have not been found yet. The aim of this work was to determine the relationship among the properties of limestone, lime, hydrated lime. The second aim has been to describe influence of the burning process on the properties of the material mentioned above. For this purpose it was necessary to get a enough wide set of data by performing a comprehensive analysis of various types of limestone. Partial dependencies have been already found on the initial results. An example might be dependence of the samples porosity to decarbonation rate or to its geological age. Due to the realization of this stage of research a coherent set of data was created. This dataset will be used for further research in this area.

Impact of Grinding Technology on Final Properties of Portland Cement

Portland cement got his name derived from the appearance of concrete that resembles sandstone located near city of Portland in England. In 1824, John Aspdin was granted a patent for the production of Portland cement.In the past, energy and economic demands on production of cement were lower than they are today. Production was characterized by a slower burning mode and coarser grinding. Product produced this way were reaching lower compressive strength.Currently there are several companies producing Portland cement. Main ones in Czech Republic are Holcim, Heidelbergcement group and Lafarge Cement a.s. Their production methods are very similar. The differences are mostly in the possibility of using local raw materials with different chemical composition and the technical equipment of factories. In the production, the main emphasis is on reducing energy and financial cost.One way to save energy and money is to use mechanical-chemical activation when grinding Portland clinker.

Impact of Milling Intensifiers on Specific Surface Area of Cement

Milling of cement is one of the more demanding procedures in cement production. During milling process, fine particles have tendency to aggregate. This paper focuses on effect of intensifiers of milling. Conventional industrial intensifiers, as well as clean basis, as are glycerol or triethanolamine were used. Milling took place in laboratory planetary mill. Mixtures with intensifiers increased their specific surface area faster than reference in first 10 minutes of milling, but after 20 minutes specific surface area of all mixtures reached maximal values. Additional milling caused reduction of specific surface area. This effect was less pronounced when intensifiers were used. Usage of intensifiers has many benefits, but it should be considered in relation to the used mill and ecological situation.