Influence of dispersed reinforcement parameters on the high-strength steel fiber concrete creep perfomance

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.