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- ItemHygric and mechanical parameters of ternary binder based plasters lightweighted by expanded perlite(IOP Publishing, 2018-07-12) Čáchová, Monika; Koňáková, Dana; Vejmelková, Eva; Vyšvařil, Martin; Bayer, PatrikThis article is focused on modern plasters with improved thermal insulating ability. The studied plasters were composed of lime, cement, ceramic powder, expanded perlite and silica sand. Regarding the matrix, three kinds of binders were used. Lime was partially replaced by ceramic powder. These waste materials show good pozzolanic reactivity and thus bring economic and ecological benefits. Portland cement was added as a third component to the mixture for the purpose of improving mechanical performance of the studied plasters. In this article, mechanical properties of designed plasters are presented. It was proved that matrix strengthening brought positive effect and eliminated the deterioration of mechanical behaviour; the final values of compressive strength were over 3 MPa. Due to desired high porosity of the studied plasters, their durability can be strongly affected by presence of the water. Therefore, in this article, the hygric parameters were studied too. Namely, the water absorption coefficient, apparent moisture diffusivity, the water vapour diffusion resistance factor and sorption and desorption isotherms belong among studied hygric characteristics. In this article, pore size distribution curves, which affect the discussed parameters, are presented.
- ItemRheological and mechanical properties of alkali-activated brick powder based pastes: effect of amount of alkali activator(IOP Publishing, 2018-07-12) Vyšvařil, Martin; Vejmelková, Eva; Rovnaníková, PavlaThe rheological behaviour and mechanical properties of alkali-activated materials prepared by activation of a brick powder by alkaline solution (alkali + water glass) is presented in this paper. The effect of quantity of alkaline activator on the rheological and mechanical properties of brick pastes prepared from two types of brick dust was monitored. The rheological investigation included the characterization of flow properties and viscoelastic properties of the fresh mixtures. Compression and bending strengths were determined at 7, 28, 56 and 90 days. These materials have a low yield stress and a high viscosity strongly influenced by the amount of alkali activator. The fresh brick pastes become liquid more easily with increasing amount of alkali activator. The rising amount of alkali activator leads to a decrease of the material cohesion. The results of rheological and mechanical properties investigation showed considerable differences in behaviour of particular types of brick dust.
- ItemEffect of particle size of waste brick powder on the properties of alkaline activated materials(IOP Publishing, 2018-07-12) Brînduş-Simuţ, Jiřina; Vyšvařil, Martin; Bayer, Patrik; Keppert, Martin; Rovnaníková, PavlaThe properties of alkaline activated brick dust mixed with water glass with a silicate modulus (Ms) of 1.0 were studied in fresh mixtures as well as hardened products in connection with the particle size of the dust. The brick dust (ground waste brick) was separated into 5 fractions according to particle size. The influence of particle size on the rheological properties of the fresh mixtures was studied via measurements of the yield stress and viscosity. The flexural and compressive strengths of the hardened products were determined after storage under laboratory conditions for 7, 14 and 90 days; the influence of 7 days of curing at 65°C on strength was evaluated as well. The microstructure of the hardened products was studied by means of porosimetry and SEM.
- ItemThe Assessment of Cement Mortars after Thermal Degradation by Acoustic Non-destructive Methods(IOP Publishing, 2017-10-25) Topolář, Libor; Kysilková, Daniela; Hoduláková, MichaelaThanks, the terrorist attacks on the worldwide interest in the design of structures for fire greatly increased. One of the advantages of concrete over other building materials is its inherent fire-resistive properties. The concrete structural components still must be able to withstand dead and live loads without collapse even though the rise in temperature causes a decrease in the strength and modulus of elasticity for concrete and steel reinforcement. In addition, fully developed fires cause expansion of structural components and the resulting stresses and strains must be resisted. This paper reports the results of measurements by Impactecho method and measurement by ultrasound. Both methods are based on the acoustic properties of the material which are dependent on its condition. These acoustic methods allow identifying defects and are thus suitable for monitoring the building structure condition. The results are obtained in the laboratory during the degradation of composite materials based oncement by high-temperature.
- ItemTernary binder based plasters with improved thermal insulating ability(IOP Publishing, 2017-10-25) Čáchová, Monika; Koňáková, Dana; Vejmelková, Eva; Vyšvařil, MartinNew kind of plasters with improved thermal insulating ability are presented in this article. Improvement was reached by utilization of lightweight expanded perlite with high porosity. The second used aggregate was silica sand. Regarding the binder, three kind were combined for the reason of better plaster performance. Pure lime, Portland cement and pozzolanic ceramic powder were employed. Basic physical properties and thermal characteristics were determined. The porosity of plasters reached desired higher value about 50% and the thermal conductivity in dry state was lower than 0.16 Wm1K1.