PERSPECTIVES OF THE USE OF MODERN BUILDING MATERIALS IN ROAD CONSTRUCTION

Abstract

The authors analyzed the foreign experience of using keyed joints in reinforced concrete span structures of bridges. Fiber concrete with polypropylene fibers was chosen as the investigated material. Such fibers are chemically neutral, water-resistant, have a high resistance to dynamic loads, reduce the risk of formation and development of cracking, increase abrasion what is important in the manufacture of road construction. Optimization of concrete composition with polypropylene fibers for concreting joints by physical and mechanical parameters was carried out. Parameters of optimization were compressive strength, tensile strength at bending, axial tensile strength, prism strength and abrasion. The authors performed a series of tests to study the behavior of fiber concrete in keyed joints. The analysis of obtained results out depending on the nature of failure, the value of the ultimate load and fiber concrete deformations were carried out. The influence on the joints strength of the cross-section reinforcement percentage and the nature of placement of the reinforcing rods was considered. It was established if to place a cross-reinforcement in two levels it increases the strength of joints in comparison with a single level with the same percentage of reinforcement. It was noted that the fracture of all samples occurred from the sear key. Cracking of fiber concrete experimental samples occurred at later stages of loading compared with samples of ordinary concrete, and the fracture was not brittle, without tearing off parts of concrete. Increase in strength is due to the chaotic placement of polypropylene fibers in concrete, and therefore, to remove fibers from concrete, it is necessary to spend more energy, which ultimately leads to an increase in strength of joint. Experimental data suggest possibility and feasibility of polypropylene fibers in concrete joints in precast concrete structures of bridges