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Influence of anticorrosive surface treatment of steel reinforcement fibers on the properties of ultrahigh-performace cement composite
Bocian, Luboš ; Ptáček, Petr (referee) ; Novotný, Radoslav (advisor)
This thesis characterized surface layer of brass on commercially available steel microfibers. Subsequently, it was studied how to remove this surface layer of brass off these microfibers. Additionally, this thesis investigated influence of removal of brass surface layer on mechanical and ballistic properties of RPC composites. It was also studied how previously mentioned surface layer of brass influences interface between steel microfibers and matrix. It was found out that the surface layer of brass on commercially available steel microfibers is uneven and that the brass fills scratches present on steel underneath the surface layer of brass. It was also found out that conc. HNO3 and mixture of NH3 and H2O2 in volume proportion of 3 : 1 can be used to remove the surface layer of brass. The only thing to consider is that steel microfibers from conc. HNO3 corrode. Flexural strength of composite made with fibers from mixture of NH3 and H2O2 is higher than flexural strength of composite made with commercially available steel microfibers with surface layer of brass after 28 and 95 days. Compression strength wasn’t significantly affected in any composite used in this thesis after 28 and 95 days. Composite made with fibers from mixture od NH3 and H2O2 showed slightly better ballistic resistance than composite made with commercially available steel microfibers with surface layer of brass. In terms of SEM analysis of interface between matrix and steel fibers of certain composite, it was found out that there was no evidence of infiltration of components of brass into matrix.
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Reactive powder concretes (RPC) with polymer latexes
Petrů, Ludmila ; Koplík, Jan (referee) ; Šoukal, František (advisor)
This thesis deals with the effect of polymeric latexes on the properties of concrete based on reactive powders. Three types of commercial latexes were used for the preparation of the samples, namely Revacryl, Duvilax and Plextol. Revacryl AE 2091 is an aqueous dispersion of styrene-acrylate copolymer with a high content of solids. Duvilax BD-20 is a homopolymer polyvinyl acetate dispersion that does not contain fillers with plasticizers. Plextol X 4002 is an aqueous, self-setting acrylic emulsion with a high content of solids. These latexes were added to the samples at concentrations of 0,20; 0,40; 0,60; 1,20 and 2,50 %. To determine the effect of latex on processability, the flow rate of the fresh mixture was measured. The main objective was to determine the ballistic resistance of modified concretes based on reactive powders. The DOP test was used for the determination. Furthermore, the change in mechanical properties was determined by adding a polymer to concrete based on reactive powders. The improvement in properties is expected to be due to the formation of a polymer film and a polymer-cement co-matrix. To demonstrate the film formation, the microstructure of the samples was observed by a raster electron microscope.
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Influence of anticorrosive surface treatment of steel reinforcement fibers on the properties of ultrahigh-performace cement composite
Bocian, Luboš ; Ptáček, Petr (referee) ; Novotný, Radoslav (advisor)
This thesis characterized surface layer of brass on commercially available steel microfibers. Subsequently, it was studied how to remove this surface layer of brass off these microfibers. Additionally, this thesis investigated influence of removal of brass surface layer on mechanical and ballistic properties of RPC composites. It was also studied how previously mentioned surface layer of brass influences interface between steel microfibers and matrix. It was found out that the surface layer of brass on commercially available steel microfibers is uneven and that the brass fills scratches present on steel underneath the surface layer of brass. It was also found out that conc. HNO3 and mixture of NH3 and H2O2 in volume proportion of 3 : 1 can be used to remove the surface layer of brass. The only thing to consider is that steel microfibers from conc. HNO3 corrode. Flexural strength of composite made with fibers from mixture of NH3 and H2O2 is higher than flexural strength of composite made with commercially available steel microfibers with surface layer of brass after 28 and 95 days. Compression strength wasn’t significantly affected in any composite used in this thesis after 28 and 95 days. Composite made with fibers from mixture od NH3 and H2O2 showed slightly better ballistic resistance than composite made with commercially available steel microfibers with surface layer of brass. In terms of SEM analysis of interface between matrix and steel fibers of certain composite, it was found out that there was no evidence of infiltration of components of brass into matrix.
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