Hlavní faktory ovlivňující modul pružnosti betonu

Abstract

One of the basic characteristics of concrete constructions under load are resistance and shape changes. Own weight, utility and random loads deformations of these structures seem relatively insignificant, taking their sizes or other materials into consideration. the more important they are in terms of stability of structure and its inner tension. Deformational concrete properties have crucial significance for large sized structures with heavy loads, such as some bridge objects on line structures, tunnels, halls, prestressed structures and high strength concrete structures. Modulus of elasticity is fundamental characteristic used for expressing elastic (reversible) concrete deformations. It is an integral part of the static calculations and is closely related to other mechanical properties of concrete such as shrinkage and creep. The actual rates of modulus of elasticity depend on the composition, quality of used components, placing and treatment. Gross aggregate, water cement ratio and air content of the concrete are the most important when it comes to the input components. Despite their essential role, properties of gross aggregate are not followed enough. Its usual characteristics required by the standards are being described; however, those that could influence the modulus of elasticity are out of the focus. Those are modulus of elasticity of the rock, petrographic characteristics of the current part of the extraction site and amount of material contamination that occur in the layer and are later included in the aggregate used for concrete. This thesis evaluates the modulus of elasticity of rocks, closeness of its quality in a particular area and differences among extraction sites of the same petrographic kind, which is greywacke. It describes how deformational properties of concrete can vary due to changes of aggregate qualities that are usually not watched. The thesis deals with finding options how to reach the required modulus of elasticity that would be in accordance with valid Eurocodes and the project requirements, through the right choice of ingredients in the Northen Moravia region.