MODIFICATION OF CONCRETE RAILWAY SLEEPERS AND ASSESSMENT OF ITS BEARING CAPACITY

The issue of concrete modification of railway sleepers remains relevant in connection with the growing demand for this product and increased requirements for the operational characteristics of one of the basic materials of the track superstructure. The problem is a partial early failure of sleepers, loss of load-bearing capacity in the early periods of operation (in the first years or after ten years). A lot of work has been done in this direction, most of them are aimed at concrete modification, but it is also worth considering the design features of the sleepers, and in order to increase the bearing capacity it is necessary to consider other ways to solve the problem. The aim of the researching was to modify the properties of concrete by polycarboxylate-based superplasticizers as concrete modifiers, determines their optimal dosages (from 0.8 to 1.1% by weight of cement) in accordance with the physical and mechanical properties of the raw materials and the required concrete workability. The sleepers considered in this article are reinforced with a wire with a diameter of 7 mm (one of the options for enlarged reinforcement). An option for additional reinforcement of sleepers in the area of the rail seat is proposed. Tests were carried out to determine the physical and mechanical properties of raw materials, the strength of concrete, and full-scale tests of the spars for crack resistance in bending were also carried out. The tests were carried out on certified equipment. According to the research results, it was concluded that for the production of sleepers that meet the requirements, it is necessary to use high-quality cements, polycarboxylatebased superplasticizers and additional reinforcement.