Tomáš Kovářík

Production of refractory chamotte particle-reinforced geopolymer composite

Geopolymer resins are obtained by alkaline activation of aluminosilicate sources where raw calcined clays are one of the suitable potentialities. Besides the fact that chemical composition has an essential effect on final properties of the geopolymer binder, the type of filler strongly affected resulting properties of such granular composite. However, very few comparative studies have been done on detail description of composite systems: binder - granular filler, in relation to aggregate gradation design and rheology properties of the mixture. The aim of this work is to develop and describe granular composite concerning workability of the mixture and kinetics of geopolymerization/polycondensation through flow behaviour. The rheological measurements indicated that initial viscosities of the mixtures and their evolution are different for various proportions of the filler. Moreover, it was demonstrated that increase in complex viscosity responds to the creation of chemical bonds and the formation of structural network. Finally, a correlation of the mechanism of geopolymer formation was carried out by differential scanning calorimetry (DSC).

The influence of metakaolin substitution by slag in alkali-activated inorganic binders for civil engineering

In this study the effect of metakaolin replacement by milled blast furnace slag in alkali-activated geopolymeric binder was investigated in accordance to their rheological and mechanical properties. It was demonstrated that slag addition into the metakaolin binder can improve mechanical properties of final products. Our investigation was focused on broad interval of metakaolin substitution in the range from 100 to 40 volume per cents of metakaolin so that the volume content of solids in final binder was maintained constant. Prepared binders were activated by alkaline solution of potassium silicate with silicate module of 1.61. The particle size analyses were performed for determination of particle size distribution. The rheological properties were determined in accordance to flow properties by measurements on Ford viscosity cup and by oscillatory measurements of hardening process. For the investigation of hardening process, the strain controlled small amplitude oscillatory rheometry was used in plane-plate geometry. For determination of applied mechanical properties were binders filled by ceramic grog in the granularity range 0-1 mm. The filling was maintained constant at 275 volume per cents in accordance to ratio of solids in dry binder. The mechanical properties were investigated after 1, 7 and 28 days and microstructure was documented by scanning electron microscopy. The results indicate that slag addition have beneficial effect not only on mechanical properties of hardened binder but also on flow properties of fresh geopolymer paste and subsequent hardening kinetics of alkali-activated binders.

Biomaterials and Nanotechnology Approach to Medical Enhancement

Over the past few decades, biomaterial science has emerged as a new field in which a regeneration or replacement of damaged tissue has become one of the main focuses. Also, great advances in the application of multifunctional nanoparticles for biomedical applications have been made. Implementation of nanomedicine in cellular, preclinical, and clinical studies has led to exciting advances ranging from fundamental to applied research. This chapter will examine the key aspects of application of traditional biomaterials, their physicochemical properties, and behavior in biological system. Moreover, the unique properties of nanomaterials are highlighted in relation to their vast nanostructural characteristics and the field of application. With 164 references.

Ceramic-like open-celled geopolymer foam as a porous substrate for water treatment catalyst

This paper presents results from experimental study on microstructural and mechanical properties of geopolymer-based foam filters. The process for making porous ceramic-like geopolymer body was experimentally established, consists of (a) geopolymer paste synthesis, (b) ceramic filler incorporation, (c) coating of open-celled polyurethane foam with geopolymer mixture, (d) rapid setting procedure, (e) thermal treatment. Geopolymer paste was based on potassium silicate solution n(SiO2)/n(K2O)=1.6 and powder mixture of calcined kaolin and precipitated silica. Various types of ceramic granular filler (alumina, calcined schistous clay and cordierite) were tested in relation to aggregate gradation design and particle size distribution. The small amplitude oscillatory rheometry in strain controlled regime 0.01% with angular frequency 10 rad/s was applied for determination of rheology behavior of prepared mixtures. Thermal treatment conditions were applied in the temperature range 1100 – 1300 °C. The developed porous ceramic-like foam effectively served as a substrate for highly active nanoparticles of selected Fe+2 spinels. Such new-type of nanocomposite was tested as a heterogeneous catalyst for technological process of advanced oxidative degradation of resistive antibiotics occurring in waste waters.

Mechanical properties of non-woven glass fiber geopolymer composites

This experimental research focuses on mechanical properties of non-woven glass fabric composites bound by geopolymeric matrix. This study investigates the effect of different matrix composition and amount of granular filler on the mechanical properties of final composites. Matrix was selected as a metakaolin based geopolymer hardened by different amount of potassium silicate activator. The ceramic granular filler was added into the matrix for investigation of its impact on mechanical properties and workability. Prepared pastes were incorporated into the non-woven fabrics by hand roller and final composites were stacked layer by layer to final thickness. The early age hardening of prepared pastes were monitored by small amplitude dynamic rheology approach and after 28 days of hardening the mechanical properties were examined. The electron microscopy was used for detail description of microstructural properties. The imaging methods revealed good wettability of glass fibers by geopolymeric matrix and results of mechanical properties indicate usability of these materials for constructional applications.

Characterization of Heat-Resistant Geocement Based on Potassium Silica Solution

The aim of this paper is detailed description of synthesis geocement composite material based on K2O-Al2O3-SiO2 system and characterization its thermal properties. The series of analytic tools were used (XRF, XRD, SEM, BET, particle-size distribution) for accurate identification of chemical and physical properties of raw material. Optimum technological prescription was determined and geocement specimens were tested for identification of mechanical and thermal properties. Three series of specimens were heated up to 1000, 1100 and 1230°C and flexural strength was determined. The thermal analysis TMA and DMA were used for characterization of heat-resistant properties. The maximum shrinkage in the range 30-1000°C was for the first run in temperature rate 20°C/min. only 3%. The heating exposure at slower rate (3°C/min.) caused reduction of shrinkage up to 1.5% at 1000°C. Geocement represents attractive thermal properties.