Investigation of the behaviour of structural lightweight concrete produced with metakaolin under elevated temperature

In this thesis, the mechanical properties of the lightweight concrete produced with various amounts of metakaolin were investigated. Before starting the laboratory study, domestic and foreign literature related with the thesis subject was examined. Five different series of lightweight concrete-mixtures were prepared by replacing the cement with metakaolin at proportions of 0, 5,10,15 and 20 % by weight. Then, physical and mechanical changes of the series were determined at the end of the 3,7,28-day curing periods. 3, 7, 28 days curing period of change in strength was examined at the end of the 28-day series in the physical, mechanical and high temperature strength after the losses were recorded. Taking three specimens one specimen from each set prepared, these specimens have been exposed to various temperatures. (400, 600, 800 o C After this operation, the losses in mechanical strength of the specimens have been determined. Scanning electron microscope (SEM) has been used to determine the changes from high-heat exposure on each specimen's internal structure. End of the study , 15% up to metakaolin additives have been found to increase the resistance of the concrete. The other physical tests ( ultrasound , porosity, such as sorptivit ) has been shown to support this conclusion . Depending on temperature increase strength loss was observed in all series , the highest temperature resistance of all doped series showed 15 %. However , especially at a temperature of 600 ° C higher the percentage of metakaolin series has declined affected by elevated temperatures. Microscopic examination as a result of the deterioration in the internal structure of the sample after high-temperature strength values are determined and are supported.