Advanced Materials Research Vol. 897

Abstract: Low-lime saturated belite clinkers were prepared under different regimes of burning in the laboratory. Development of compressive strengths of the obtained belite clinkers was evaluated in relation to the reactivity of raw meals, burning temperature and time, and degree of lime saturation. Electron and optical microscopy, X-ray diffraction analysis and high-temperature microphotometry were the methods used for characterization of belite clinkers. It was discovered that the quickly-burnt belite clinker has unexpectedly lower hydraulic activity with respect to the longer-time burnt, recrystallized clinker. The reason could be little contamination of its crystal lattice by secondary oxides as determined by electron microanalysis.

Abstract: 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.

Abstract: This work deals with proposal and testing of cement mixtures normative called as Bricking cement. The norm demanded properties were tested on these cement mixtures depending on amount and type of used chemical admixtures. Technically it is possible to define this mixture binder as premix binder for ambulatory preparation of mortar and plaster admixtures.

Abstract: 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.

Abstract: The course of hydration and the resulting structure in binders containing pozzolan and latent hydraulic materials is still widely investigated area. In this work we studied the course of hydration by calorimetry of cement with several types of different reactive admixtures. After determining the results of hydration the DTA / TG analysis of the resulting material was carried out. Qualitative comparisons of resulting products are primarily implemented.

Abstract: 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.

Abstract: Influence of typical ceramic deflocculant – sodium hexametaphosphate – on the rheological properties (viscosity) of calcium aluminate cement paste, porcelain raw materials mixture (casting slip), and fired porcelain body respectively, was determined. It was used two different typed of calcium aluminate cements (from two sources – producers - Istra, Almatis) with different content of Al₂O₃ (40 % and 70 %). Sodium hexametaphosphate decreases of water content needed to prepare slip casting with constant viscosity. Deflocculant increases the modulus of rupture MOR of dried green body and its bulk density. Sodium hexametaphosphate admixture is very suitable for the creation of porcelain body with low porosity after firing.

Abstract: This work is opening study in issue of potential utilization of high-speed shredder for portland cement grinding. The article deals with comparison the influence of traditional ball mill with high-speed shredder on shape and size of grains.

Abstract: The paper presents the results of the study of selected fiber-cement boards parameters influenced by sulphur-oxidising (Acidithiobacillus thiooxidans) and sulphur-reducing bacteria (Desulfovibrio desulfuricans) attack. The experiments proceeded during 80 days under laboratory model conditions. The surface changes, chemical composition and pH of leachates as well as weight changes were investigated. The more extensive leaching of silicon and calcium ions from the cement matrix was confirmed under bacteria influence. The pH of liquid media has been settled to 7 and 9 for Acidithiobacillus thiooxidans and Desulfovibrio desulfuricans, respectively after initial increasing. Very small decrease in weight of samples in range 0.001 - 0.93 % was measured after the experiments.