| Abstract [eng] |
The aim of this master's thesis is to investigate the efficiency of self-healing concrete using additives whose effect on concrete regeneration has not been fully investigated. Also to test alternative ways of forming crystals that can fill a crack in concrete structures and to test a new method for evaluating the effectiveness of self-healing concrete. An analysis of literature and research was performed during the work. General knowledge about the basic principles of self-healing concrete, necessary conditions and test methods has been collected. The results of scientific research and the theoretical applicability of little-studied materials for concrete healing are analyzed. In the experimental part of the work, tests were performed to find out the influence of various mineral and polymer additives on crack sealing. During the tests with cement paste samples, it was found that the additives of amorphous silica, calcium stearate and sodium alginate used in the samples were not effective in closing the crack. The possibilities of selh-healing of cracked concrete specimens were investigated using additives based on the formation of syngenite, ettringite and calcium carbonate in the crack. The results of this study show that the samples consisting of a mixture of potassium sulfate and anhydrite were the most effective in self-healing, however the efficiency of self-healing concrete is highly dependent on the amount of water in the crack. In this master‘s final degree project, the crack closure efficiency was evaluated by the crack width measurement and water permeability methods. However, the tests showed that the evaluation of the crack closure efficiency by measuring the crack width on the sample surface is not suitable for reliable quantitative analysis. In the experimental part of the work it was also tested the possibility of the formation of crack-filling crystals using the method of liquid-liquid diffusion. The results show that crystals of the crack-filling material can be formed in aqueous solutions of materials, and the method of crystal growth materials in aqueous solutions can be adapted to the development process of new crystalline additives. Taking into account that the assessment of self-healing concrete efficiency is still not standardized, a new methodology for self-healing efficiency assessment was developed during the master's final project. During the test, it was found that full crack closure can be achieved even in a smooth crack by using water-retaining means. The methodology used may be promising, but the methodology needs to be improved in order to perform a highly accurate quantitative analysis. |
