Tensile Strength of Nanofibrous Concrete
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Journal of Engineering Physics and Thermophysics, Vol. 93, No. 4, July, 2020
NANOSTRUCTURES TENSILE STRENGTH OF NANOFIBROUS CONCRETE E. A. Sadovskaya,a S. N. Leonovich,b S. A. Zhdanok,c and E. N. Poloninaa
UDC 624.012
Results of testing nanofibrous-concrete test beams for axial tensile strength, for cleavage tensile strength, and for compressive strength have been given. Concrete matrices covering a broad spectrum of compressive-strength classes of concretes of construction grade were used as a basis. A macrolevel fiber (steel or polymeric) or a nanolevel fiber (carbon nanotubes) was made part of a concrete matrix. An increase of 80% in the axial tensile strength and of 145% in the cleavage tensile strength was recorded in the nanofibrous-concrete test pieces. Diagrams of axial tensile straining of the test pieces have been obtained. Keywords: nanostructured carbon, nanotubes, fiber, nanofibrous concrete, axial tensile, cleavage, and compressive strength. Concrete belongs to the category of materials with brittle fracture. Increasing the fracture toughness of concrete is a relevant and promising trend in building materials science. It is believed that in concrete there are always certain incipient cracks (defects) with which the main crack begins to develop. The fracture toughness of concrete (its crack resistance) may be increased not only by single-level (traditional) reinforcement of its structure, but also by multilevel dispersed reinforcement. Dispersed reinforcement of concrete by fiber is capable of retarding the formation of a main crack in it. Concretes of high fracture toughness are in demand in the areas where higher-than-average crack resistance and tensile strength, and also high impact strength and wear resistance, are required. Dispersed reinforcement of a concrete matrix contributes to the fundamental change in the conditions and energy of formation of cracks in the material′s structure. Fibrous concrete is a concrete containing fibers as part of it. These fibers play the role of a dispersed reinforcement which improves the strength of a concrete matrix. An analysis of the literature has shown that such concrete is water-resistant, possesses high tensile and breaking strength and a higher-than average elastic modulus, is resistant to chemical substances, atmospheric actions, crack formation, and wear, and is noted for its frost resistance, fire resistance, the absence of shrinkage, and the high resistance to impact [1–5]. The objective of the present work is to assess the influence of the reinforcement of concrete by various fibers on its axial tensile strength, cleavage tensile strength, and compressive strength. Investigations were carried out at the "Atomstroyexport" Construction Laboratory (Russia) located at the construction site of the Belarusian Nuclear Power Plant (NPP) in accordance with requirements of the National Standard of Belarus (STB), the International Standards Organization (ISO), and the International Electrotechnical Commission (IEC) STB ISO/IEC 17025-2007. In the experiments,
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