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The effect of appication of fine organic fibers to cement composites
Kavka, Lukáš ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
This bachelor thesis describes the effect of using fine organic fibers in cement composites. In the theoretical part of bachelor thesis a composite material was defined and his individual components were described. Then was created a research of information about organic fibers focused on natural fibers. The basic parameters of cellulosic fibers and polypropylene fibers, the effect on the properties of cement composites and their application in practice were described. In the practical part there were created a reference concrete and 3 types of concrete with the addition of various types of organic fibers. The influence of fiber addition on the properties of fresh and hardened concrete were investigated. Another task of practical part was monitored the resistance of cellulose fibers in acidic and alkaline media in which the tested fibers were deposited. The development of pH solutions was examined over time.
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Study the abrasion resistance of concrete
Kolková, Kristína ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
The thesis deals with the issues of concrete abrasion resistance and it consists of a theoretical research part and an experimental part. The types of abrasion affecting concrete construction and abrasion effect of flowing water-borne sand are described in the theoretical research part. A substantial part is dedicated to the impact of concrete properties and to each material of the concrete mixture on the abrasion resistance. The impact of addition of various types of fibers is inquired. The mixtures with the addition of 2 kg.m-3 and 4 kg.m-3 of basalt fibers and the addition of 1 kg.m-3 and 2 kg.m-3 of polypropylene fibers are designed in the experimental part. The mixtures are compared to a reference mixture without fibers. Density and consistency of fresh concrete settling at 5 minutes are determined in fresh condition. Density, compressive strength, tensile strength, watertight, concrete absorption and bending tensile strength are determined on hard concrete. The impact of the addition of fibers to the concrete abrasion resistance is inquired using the Bohm abrasion method and wheel abrasion method. A water jet is used as another method for testing abrasion resistance and for comparing the suitability of the used methods.
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The effect of appication of fine organic fibers to cement composites
Kavka, Lukáš ; Hela, Rudolf (referee) ; Bodnárová, Lenka (advisor)
This bachelor thesis describes the effect of using fine organic fibers in cement composites. In the theoretical part of bachelor thesis a composite material was defined and his individual components were described. Then was created a research of information about organic fibers focused on natural fibers. The basic parameters of cellulosic fibers and polypropylene fibers, the effect on the properties of cement composites and their application in practice were described. In the practical part there were created a reference concrete and 3 types of concrete with the addition of various types of organic fibers. The influence of fiber addition on the properties of fresh and hardened concrete were investigated. Another task of practical part was monitored the resistance of cellulose fibers in acidic and alkaline media in which the tested fibers were deposited. The development of pH solutions was examined over time.
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Improvement of mechanical properties of the sintered ceramics by plasma remelting
Ctibor, Pavel
Ways how to improve mechanical properties on a surface of bulk ceramics are drawn. In the experiments the author reach surface treatment by plasma torch producing thermal plasma and usually utilized for plasma spraying. Commercial bulk ceramic materials produced via sintering or casting were tested. The materials were members of ternary systems magnesia - alumina - silica and zirconia - alumina - silica. Before and after thermal treatment the microstructure was studied and the microhardness was measured on materialographically polished cross sections using Vickers indentation (HV) in surfacial layers and also deep inside the bulk body. Slurry abrasion resistance (SAR) was determined according ASTM G 75 standard. Various degree of improvement of HV and SAR was detected on treated samples. The microstructural character of completely remolten surfacial layer, partly influenced intermediate layers and original bulk body is discusses in connection with evaluated mechanical tests.
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