The purpose of the master's thesis is to verify the durability of concretes and mortars that are exposed to aggressive environmental conditions, with controlled development of their physical and mechanical properties. Controlled mechanical properties of concretes and mortars are compressive, bending and splitting tensile strength and dynamic modulus of elasticity. What the concretes and mortars have in common are the same components and a water-cement ratio of 0,45, where mortars do not contain coarse aggregates. In this thesis, we try to establish the impact of the chemical alkali-carbonate reaction (ACR) on mechanical properties, weight and length of mortar samples. The mortars were made with four different carbonate aggregates with the nominal fraction 0/4 m, and by combining two different cements. The prism-shaped samples (40x40x160 mm) were exposed to different accelerated ageing conditions over a period of 14 months (a solution of deionised water or 1 mol sodium hydroxide, and a temperature of 20 °C or 60 °C). We also tested the resistance of the concrete samples in the case of a cyclic freezing and thawing load, up to 250 cycles. Before the freezing/thawing test, we also tested their mechanical properties. We determined their pressure strength, splitting tensile strength and resistance to water penetration. However, we performed these tests before the start of loading freeze/thaw cycles, the influence of which was checked by determining the dynamic modulus of elasticity of concrete.
The results have shown that ACR affects mechanical properties of dolomite mortar samples, but not their mass and length. Therefore, we have concluded that ACR is not an expansion reaction. We have also determined a high resistance to freezing/thawing and high watertightness of all concrete samples. This means that we have designed concrete mixtures that are capable of providing a long lifespan of reinforced concrete elements, even up to 200 years and more.
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