Solid State Phenomena Vol. 321

Abstract: The effect of fluidized fly ash (Tisová, ČEZ Group Czech Republic, class C according to ASTM C618) on the porosity (water absorption, bulk density, capillarity) and water impermeability of brick body used for the production of clay roofing tiles (Wienerberger, Czech Republic). The properties of plastic body (mixing water, drying shrinkage) are discussed too. The addition (10 %wt) of fluidized fly ash in the raw materials mixture for the production of clay roofing tiles generally reduces the sensitivity to the formation of reducing cores during firing thanks to higher porosity of dried green body (higher mixing water) - this is also related to the higher water absorption and capillarity of the fired body and hence to the impaired water impermeability when the fly ash is used.

Abstract: The mineral mullite has many outstanding refractory properties. The content of aluminum oxide in the raw material is the basic factor influencing the content of mullite in the final product. Depending on Al₂O₃ content, silica-alumina materials can be divided into fireclay and high-alumina with the Al₂O₃ content of 45 % and more. The study describes the influence of raw material, the influence of homogenization of raw material and influence of firing temperature on the mullite formation in fireclay refractory material. Three kinds of refractory clay with different chemical composition were used as raw material for fireclay grog production. Three kinds of homogenization and three different temperatures were studied as factors influencing mullite formation. Powder X-ray diffraction was used to determine mullite content in material. Quantitative phase analysis was conducted by the Rietveld method. Mullite crystals morphology was observed by scanning electron microscopy.

Abstract: Currently, the use of board materials as a material intended for the dry construction of building structure cladding in the building industry has become widespread. The most common types of board materials include wood-based boards (particle, fibre, laminated / plywood, oriented strand boards [OSB]), cement-bonded particleboards and gypsum plasterboards or gypsum fibre boards. In the case of board materials based on inorganic binders, these are most often represented by boards in which the fillers used are bonded by plaster or cement. Wood can then be used as filler, which is predominantly an assortment of inferior-quality trees or comes from a short rotation coppice, treated by various technological processes. Microstructure and material composition have the greatest influence on the physical and mechanical properties of the boards. The use of the boards in the internal or external environment is determined by their individual properties. Another indicator for the possible use of boards is the form of moisture with which the board comes into contact after installation into the structure. For the external environment, the boards have to withstand mainly liquid moisture; in contrast, in an internal environment, the boards come into contact mainly with air humidity. The diffusion properties of the individual products are also crucial for the overall design and use of the boards for structure cladding.

Abstract: Optimization of complex shrinkage-reducing additives (further, SRA’s), consisting of ordinary portland cement clinker (further, OPC clinker), salt-electrolyte and surfactants, is provided for prevention of steel reinforcement corrosion due to shrinkage mitigation in alkali-activated slag cement (further, AASC) fine concrete. Modification of AASC by SRA included 0.3 % sodium lignosulphonate, 0.15 % sodium gluconate, 1.4 – 2.0 % NaNO₃ and 6.5 - 7.7 % OPC clinker (by mass of granulated blast furnace slag) provides shrinkage reduction from 0.984 up to 0.560 – 0.605 mm/m (t=202 °С, R.H.=65 %). Unlike, SRA presented by the mentioned system with 1.50 - 1.59 % Na₂SO₄ and 4.0 - 4.65 % OPC clinker causes shrinkage mitigation from down to 0.625 - 0.640 mm/m. In addition, SRA with 1.80 - 2.05 % Na₃PO₄ and 4.0 - 4.6 % OPC clinker minimizes shrinkage to 0.713 - 0.700 mm/m. Shrinkage mitigation in modified AASC fine concrete is explained by less water, higher crystallinity of hydrated phases as well as by formation of minamiit (Na,Ca_0.5)Al₃(SO₄)₂(OH)₆, calcium hydronitroaluminate ЗСаО∙А1₂О₃∙Са (NO₃)₂∙10Н₂О and calcium hydroxylapatite Са₁₀(РО₄)₆(ОН)₂ crystals versus salt-electrolyte, i.e. Na₂SO₄, NaNO₃ and Na₃PO₄ agreeably. The 28 day compressive strength of modified AASC fine concrete is not less than the reference one (48.0 - 56.0 МPа).

Abstract: The electrical conductivity of concrete can be achieved by adding steel wires or functional fillers. Commonly used fillers are nanotubes, carbon black, nickel powder and so on. These fillers are expensive, but there is a possibility to use waste materials. This is the subject of this experiment. The conductive properties of conductive sand, sludge from the wire drawing process, iron grinding dust waste and waste carbon were verified. From these fillers, waste carbon showed the best electrical properties (impedance). The impedance of the waste carbon was 0.31 Ω and the impedance of the cement composite containing 70% of the weight of waste carbon was less than 670 Ω.

Abstract: This paper concerns the degradation of fire protection boards in the ceiling structure of the 4^th tube of Elbtunnel in Hamburg, Germany. During the routine inspection an irregularity in the ceiling material was observed. Based on this inspection five cores were drilled out of the fire protection boards. These samples were examined and analyzed using visual, X-Ray Diffraction analysis (XRD), Differential Thermal Analysis (DTA) and Scanning Electron Microscopy (SEM) images. From the inspection and the analysis of data it was possible to conclude the cause of the material corrosion of the autoclaved calcium silicate fire protection boards.