Master of Science / Department of Civil Engineering / Asadollah Esmaeily / Reinforced concrete exceptional durability is a major reason why it is the most popular structural material in many infrastructures around the world. Most concrete structures serve for several decades; therefore problems of concrete durability gradually arise. To insure that concrete structures perform functionally, it is necessary to maintain and inspect them regularly. The durability of the reinforced concrete structures generally depends on four major factors: structure design and construction, maintenance, concrete aggregates, and environmental conditions. The most common causes of concrete deterioration are carbonation, design and construction errors, alkali-aggregate reactions, freeze-thaw cycles, and corrosion. Each type of concrete deterioration has its own signs and characteristics. Choosing the best repair technique to address concrete deterioration requires specific analysis and tests to find the cause of the deterioration and the extent of the damage. This study analyzes concrete structures inspection techniques to recognize the source of the problem and the part of the structure which has been affected. Choosing the most proper repair and strengthening techniques to prevent the structure from getting exposed to any further environmental and chemical are the next steps.

The deliberate use of fly ash in the production of concrete has been used for decades, but recent trends tend to maximise its utility properties. These are different types of activations from chemical through thermal to mechanical. An alkaline agent is added to chemical activation which, by etching the glass structure of the ash grain, promotes its reactivity. Mechanical activation is mainly focused on granulometry and particle size distribution curve. In this thesis three mechanical activation methods are compared: separation the ash into fractions by grain size, mixing these fractions to achieve the ideal particle size distribution curve and grinding. Four types of ash were collected from the Tušimice power plant – ash from individual electrostatic separators (I, II and III) and SESYP ash which represents the total volume of production. Ash from individual separators differ not only in the particle size but also in the chemical composition and reactivity. Better properties generally have smaller ash particles. This is used by mechanical activation by sorting. When mixing the individual ash fractions, the aim is to achieve an optimal grading curve of either the ash itself or the fine particle set in the concrete. In this work, ash is only used to calculate the mixing ratio and the grading curve according to Funk was selected as optimal. The last compared option of activation was grinding ash. Grinding was carried out in an industrial mill for 15, 30, 45, 60 and 75 minutes. The efficiency of the modified ash was monitored for cement paste in terms of rheology and for concrete in terms of consistency, strength and durability. Based on the results we can say that mechanical activation by sorting is suitable for special purposes, but it’s necessary to realise that coarser ash fractions remain unused. When mixing the fractions to ensure matrix density, the efficiency was shown mainly on the durability characteristics. Grinding cause positive effect.