Introduction. In reinforced concrete structures, the ends of reinforcing bars are anchored in the concrete by launching the reinforcement beyond the considered section for the length of the force transfer zone from the reinforcement to the concrete as well as by using anchoring devices. If the required design length of the reinforcement cannot be ensured, special measures to anchor the reinforcement bars are applied [1, p. 5.36]. One of these measures is to install special anchoring devices in the form of plates at the ends of the longitudinal bars. When anchoring devices in the form of plates, special attention is paid to the welding type of the plate with the bar, which should prevent the bar from being pulled out when longitudinal forces from external load are applied. Materials and methodology. The material to be investigated was reinforcing bars of class A500C with diameters of 25 and 32 mm, connected at the ends to metal plates by means of contact welding. Holes with a diameter equal to the diameter of the reinforcement were drilled in the metal plates. The bars were inserted into the holes flush with the surface of the plates and welded to the plates by one and double sided welding. A total of two bars were used per welded joint. The strength of welded connection of reinforcing bars with plates was determined on the tensile testing machine HMS-100 by applying maximum tensile force to reinforcing bars. The fracture pattern of each reinforcing bar to plate joint was noted. The results of the experiment. As a result of the experiment, it was found that the destruction of the connection between the two reinforcing bars of 25 mm and 32 mm diameter and the metal plate during one-sided welding occurred by destroying the welding connection and pulling the bars out of the plate. When the bars were joined on both sides, there was no pulling out of the plate. In this case, one 25-mm-diameter bar joint is out of service due to bar breakage in the area of contact with the weld and the other is due to the exhaustion of its physical yield strength. The destruction of the 32mm diameter bars and metal plate joint in the two-sided welding process was due to the rupture of one bar in the area of its contact with the weld and the cracking of the other bar's contact with the weld. Conclusions. As a result of the experiment, it was found that the strength values of the welded connection between reinforcing bars 25 mm and 32 mm in diameter and a metal plate at bilateral welding were 1,33−1,36 times higher than those at one-sided welding.
Problem statement. These days, the use of secondary waste generated as a result of human activity is a relevant issue in the construction industry. One of the directions of realization of this task is the production of light structural and heat-insulating concrete by using light aggregates − industrial waste. The analysis of the current state of light concrete development and research showed that on the basis of production waste, structurally heat-insulating products made of light concrete can be obtained, which, unlike products made of heavy concrete, will significantly reduce the load on building structures and increase their heat-insulating and sound-insulating ability. In addition, the use of industrial waste as filler will lead to a decrease in the cost of construction products. The analysis of the publications showed that light structural and heat-insulating concrete can be obtained on light aggregates, such as granulated slag, cullet, waste from the processing of rubber tires, etc. It is known to use granulated slag with a bulk weight of 880 kg/m3 to obtain light structural and heat-insulating concrete with a bulk weight of 1 720−1 780 kg/m3 and a compressive strength limit of 7,3−8,2 MPa [1]. However, nowadays, in connection with the reduction of metallurgical production, the volume of such slags production has significantly decreased. In literary sources there is information about the use of cullet with a volume weight of 700 kg/m3 for the production of light concrete [2]. However, the widespread use of cullet is restrained due to the economic component, namely, that secondary processing of cullet is more effective for the manufacture of new glass-based products. It is known to use rubber crumb with a bulk weight of 300 kg/m3 with a fraction of 1−6 mm, which is formed as a result of processing rubber automobile tires, in construction [3]. The introduction of rubber crumb into the composition of the concrete mixture leads to a decrease in the mass of structures and an improvement of its deformable, heat-insulating and sound-insulating characteristics. Analysis of the production technology of polypropylene containers [4] showed that during the production of such containers aggregate and fiber are formed. The aggregate is blue or transparent granules, most of which are triangular and rectangular in shape. The water absorption of polypropylene aggregate is 8,6 %, and its density is 1,06 g/cm3. The specified information source provides data on the use of polypropylene fiber only, and there is no information on the use of aggregate. The purpose of the article was to determine the possibilities of using light aggregate − a production waste polypropylene containers, to obtain compositions of light constructive and heat-insulating concrete. At the same time, the goal of researching the strength characteristics of these concretes depending on the amount of aggregate in the mixture was also set. Conclusions. The possibility of using light structural and heat-insulating concrete in warehouses as a filler for polypropylene container production waste is considered. Studies of the compressive strength and volumetric weight of concrete showed the possibility of obtaining light concrete with a volumetric weight of 1,395 to 1,805 kg/m3 when achieving a concrete grade of compressive strength of M25 to M250. In our opinion, the use of light concrete with a volume weight of 1 625 to 1 805 kg/m3 and a compressive strength grade equal to M100−M250 will be the most acceptable for the construction of buildings and structures in terms of structural and thermal insulation characteristics. In the future, it is necessary to conduct tests of these concretes deformable characteristics with the establishment of their elastic characteristics and concrete classes in terms of strength.
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