Ингушский государственный университет, г. Магас, Россия Аннотация. В статье представлены результаты экспериментального исследования прочности при изгибе сталефибробетонных образцов (СФБ) после воздействия высоких температур. Рассмотрены свойства СФБ на основе высокопрочной цементно-песчаной матрицы при армировании пятью различными видами фибры. Процент содержания каждого вида фибры по объему составлял от 0,5 до 6,0%. Все виды фибры имели различные прочностные и геометрические характеристики. Результаты исследований показали, что прочность на растяжение при изгибе образцов СФБ, в диапазоне воздействия температур от 20 до 1100 о С, зависит от объемного содержания фибры и ее прочностных и геометрических характеристик. Практически полное разрушение СФБ наблюдалось при достижении температуры 1100 о С для всех рассматриваемых видов фибры и при всех процентах армирования. Остаточная прочность при такой температуре не превышала 5МПа.
Introduction. At the present time, in the construction of nuclear power plants (NPP), non-removable formwork made of high-strength steel fibre concrete (SFRC) is used. Due to improved physical and mechanical properties and high adhesion to monolithic concrete, the SFRC formwork is a load-bearing element. The result is a structure with combined reinforcement in the form of bar reinforcement and high-strength SRFC layers. The calculation of the actual stress-strain state of such structures requires knowing the design characteristics of used materials. High-strength SFRC is understudied material, and research of its properties, especially under long-term loads, is a crucial task. Materials and methods. Experimental studies of the effect of dispersion reinforcement parameters (type of steel fibre and its volume) on the creep value of SFRC made on a high-strength cement-sand matrix have been carried out. The research was carried out on the same matrix composition for three types of steel fibres suitable for the manufacture of 30 mm formwork sheets with a thickness of 30 mm, and most commonly found the in Russian market. A volumetric fibre content of up to 6 % was considered in the study. The load level is 0.3 of the breaking strength (prism strength). Results. The actual values of the SFRC creep parameters required to carry out the calculations of structures with combined reinforcement. Conclusions. It is found that the introduction of steel fiber up to 6 % provides a reduction of ultimate creep measure up to 20 % as compared to a fine-grained matrix. However, with up to 1.5 % volumetric content of fibre, an increase of up to 10 % in creep may also occur as a result of matrix decompaction. In the view of the large number of factors affecting the properties of SFRC, the calculated characteristics should be determined experimentally.
The paper presents results of experimental and numerical modeling of flexural behavior of RC beam strengthened be stay in place SFRC sheet formwork in a tensioned zone. Analysis of influence of the SFRC on crack propagation. As a result monolithic concrete provides the perception of tensile forces before the formation of main cracks in the steel fiber concrete.
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