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Polymer-silicate composite based on alternative raw materials under conditions of increased temperature
(Elsevier, 2016-08-03) Melichar, Tomáš; Bydžovský, Jiří
The paper presents research into studying the properties of composite materials with polymer-silicate matrix and porous (lightweight) filler. Specifically, the matrix based on cement substituted by 35% of alternative raw material was considered. In case of filler aggregate based sintered ash was used. Investigated materials were exposed at high temperatures. Thermal loading took place gradually in temperature increments of 22 °C (reference conditions), 400, 600, 800 and 1000 °C with subsequent controlled cooling. Attention was also focused on various ways of cooling – slow in the furnace (1 °C/min) and immersion in water (bath temperature c. 18 °C). Suitability of matrix modification and use of porous fillers based on alternative raw materials was proved by set of analyses. After exposure in an environment with a temperature of 1000 °C followed by quench cooling was set residual compressive strength of about 40%, which is relatively high for this type of the matrix. The curves of residual strength with different types of cooling are intriguing too. Selected samples were also investigated by using micro/structural techniques, where the emphasis was placed on the formation of any defects related.
Flexure response of thermal loaded concrete specimens by acoustic emission method
(EDP Sciences – Web of Conferences, 2017-05-24) Pazdera, Luboš; Topolář, Libor; Mikulášek, Karel; Smutný, Jaroslav; Hoduláková, Michaela; Chobola, Zdeněk; Seelmann, Herbert
The response to fire of concrete structural members depends on the thermal, mechanical, and deformation properties of concrete. These properties vary significantly with temperature depending on the composition and characteristics of the concrete batch mix as well as heating rate and other environmental conditions. The paper presents the effects of a high temperature on selected physical properties of concrete. The main aim of the article is the evaluation of monitoring concrete properties loaded in a few thermal steps up to 1200 °C. Therefore, the concrete specimens were heated in a programmable laboratory furnace at a heating rate of 5 °C/min. The specimens were loaded at six temperatures, 200 °C, 400 °C, 600 °C, 800 °C, 1000 °C, and 1200 °C maintained for 60 minutes. The acoustic emission activity and some material characteristics were evaluated in a three-point bending test.
Effect of firing temperature on the structure of the aggregate from sintered ashes
(Elsevier, 2016-08-03) Černý, Vít; Tůmová, Eva
Production of artificial aggregate from ashes is worldwide known technology that uses up to 100% of ash in the mixture. There are known two types of aggregate. First is based on binders and known as cold-bonded. Second type of aggregate is produced by self-firing process that uses a content of combustible substances in the mixture. After ignition this fuel generates enough energy for the sintering process. The paper gives an account of the influence of parameters of ash and conditions of firing on the quality of ceramic body made from ash. Temperatures of 1050 °C, 1150 °C and 1200 °C were examined. The research focused on the structure of the ceramic body as well as its physic-mechanical parameters. The results show also that firing temperature is essential for forming the structure. An important indicator is the share of melt that form a solid ash body.
Composites Based on Alternative Raw Materials at High Temperature Conditions
(Budapest University of Technology and Economics, 2017-10-24) Melichar, Tomáš; Bydžovský, Jiří; Dufka, Amos
This paper presents newly developed polymer-cement composites. The primary binder (cement) was partially substituted by use of blast-furnace slag and high-temperature fly ash. A lightweight aggregate – agloporite (grain size in range 1–2 mm) was used among other components. This porous aggregate is produced from energy by-products (fly ash). Attention was focused on the behavior of the composites when exposed to elevated temperatures (400 °C–1,000°C). The influence of several different methods of temperature decrease was assessed – slow (in furnace 1°C/min) and rapid (laboratory ambient 22°C and water bath 18°C). Specific dimensional changes were determined, including strength characteristics and bulk density.
The Effect of the Wear of Rotor Pins on Grinding Efficiency in a High-speed Disintegrator
(Kaunas University of Technology, 2018-02-19) Dvořák, Karel; Dolák, Dušan; Paloušek, David; Čelko, Ladislav; Jech, David
One of the directions intensively investigated in the field of milling is high-energy milling (HEM). One type of HEM is high-speed grinding in high-speed disintegrators. This type of mill is particularly suitable for the grinding and activation of fine powder materials. It has several advantages, such as a very intensive and continual refining process. One disadvantage is that its grinding pins are prone to abrasion, which may result in a decrease of the efficiency of grinding. This effect was investigated in this paper.

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