DESIGN AND TECHNOLOGY OF DURABLE CONCRETE FOR SEA PORT AND TRANSPORT STRUCTURES IN CONDITIONS OF FROST EXPOSURE

Currently, the design of structures with a service life of 50 years in conditions of frost exposure is carried out on the basis of regulatory documents that recommend requirements for concrete quality indicators, its composition and materials for its manufacture. To a certain extent, this is a prescriptive principle, since the recommended requirements adopted during the design process are mandatory at the construction stage. The level of requirements depends on the aggressiveness of the environment and the parameters of temperature influences. As a result of laboratory selection, the working composition of concrete is determined, on the basis of which the technology of concrete works is being worked out. To ensure the service life of concrete for 50 years in an aggressive environment of class XF 4 with frost exposure, it is recommended to apply the following restrictions to the composition and quality indicators of concrete: water-cement ratio (V/C) – not higher than 0.45; cement consumption – not less than 340 kg/m3; air intake – at least 4%; concrete strength class – at least B35; brand for frost resistance – depending on the air temperature in winter in the construction area. A number of restrictions are set to the quality of materials for concrete (cement, crushed stone, sand, water) and indicators of technological properties of the concrete mixture. It should be noted that calculation methods for selecting the composition of the required frost resistance have not been developed. Therefore, the composition of concrete for the required grade of frost resistance is determined by the selection method. In this regard, the selection of the composition of concrete for frost resistance is a long, complex and time-consuming process performed by high-level technologists. Computational methods of durability prediction are developed to optimize design solutions by taking into account the actual operating conditions of structures and the use of materials with quality indicators sufficient to ensure the required service life of structures in specific operating conditions. The development of methods for calculating the durability of concrete determines the need to investigate the effectiveness of technological techniques used in the manufacture of structures and the boundary limits of the requirements for concrete technology to ensure the durability of structures in conditions of frost exposure.