Papers by Keyword: Hardened Concrete

Abstract: This paper highlights the importance of strength correction factors for a correct assessment of concrete compressive strength as a destructive test is performed. Full-scale reinforced concrete columns were prepared and the experiment consists of the extraction of cores (core diameter of 64 mm, 79 mm, and 103 mm) to carry out destructive test. The results show that the assessment of the compressive strength of concrete depends strongly on the aspect ratio and the diameter. Furthermore, the comparison between the core compressive strengths of samples with an aspect ratio of one and two could be considered as non-conventional. In addition, a likely presence of a size effect contributes to complicate the assessment of the actual compressive strength of concrete. A need of codes unification account for correction factors to interpret the equivalent compressive strength of concrete has been discussed.

Abstract: Nowadays, applying new materials is widely used in concrete construction to study their effects in enhancing the properties and the durability of concrete. This research includes studying the using of manufactured aggregate, which is so-called '' Anti-slip sand '' in specific proportions to know its influence on strength properties of normal strength hardened concrete which involves compressive strength, flexural strength, tensile splitting strength, and density. Anti-slip sand at different rates of (25%, 50%, 75%, and 100%) replaces the natural sand in the concrete mixture to investigate its effect on the properties of concrete. The study shows that the best results of concrete properties are found when replaced the natural sand by 100% of anti-slip sand. Compressive, flexural and tensile strengths of concrete are increased with increment ratios of (44%, 40%, and 20%) respectively compared with other concrete mixture contains only natural sand. In addition, the study shows that the density of hardened concrete is decreased from 2420 kg/m³ in concrete with 100% natural sand to 2360 kg/m³ with a decrement ratio of 2.5% in concrete with 100% anti-slip sand.

Abstract: Port infrastructure facilities, located in cold climatic zones in contact with sea water, are destroyed due to carbonation of concrete and sulfide corrosion. The restoration of the reinforcement protective layer by standard methods does not provide high-quality grip of the concrete structures that has undergone destruction and the repair concrete. The study of the “old” and “new” concrete grip using forced heating of the “new” one shows that mixing water with cement clinker components dissolved in it penetrates through the pores and capillaries deep into the “old” concrete to a depth of 60–70 mm under the temperature factor influence. After hardened concrete got its standard strength, it exceeds concrete grip, hardened under normal conditions by 30%.

Abstract: he experimentation was to study the effect to cement concrete surface flexural strength by simulating the different natures and thickness of cement mortar, The slump was defined as 20mm and 70mm, on behalf of the low plasticity of concrete and plastic concrete, the three conditions of the surface mortar thickness 25mm, 15mm and 5mm was to simulate the different thickness of mortar extracted during concrete construction,which adopted three different mortar ratio and mortar consistency, the concrete specimens with the 150*150*550mm steel mould were made from concrete and the surface layer of mortar,the specimen surface as a curved flat was to determine the surface flexural tensile strength.The results show that: the surface flexural strength of concrete is affected by the components,natures and thickness of cement mortar, the higher the surface mortar strength is, the higher concrete surface bending strength is.