Influence of technological and environmental factors on the behaviour of the reinforcement anchorage zone of prestressed concrete sleepers

The article analyses the influence of technological factors on variations in the stress and strain state during the production of prestressed concrete sleepers. The paper focuses on technological damage to the anchorage zone and its influence on concrete and the pretensioned reinforcement of the last prestressed concrete sleepers located by abutments. The article presents the calculation principles of stresses caused by thermal and humidity deformations, compares theoretical and experimental results and specifies the nature of damages. The paper deals with concrete structure and an interface between reinforcement and concrete of new and three years old prestressed concrete sleepers, explores the results of laboratory tests on deteriorating the ends of new prestressed concrete sleepers under freezing and thawing cycles, looks at changes in concrete structure and the interface between reinforcement and concrete at the ends and in the middle of prestressed concrete sleepers applying a scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). Secondary ettringite formation (DEF) in concrete micro-cracks and at the interface between reinforcement and concrete and elemental composition of the formed crystals have been determined. Significant difference in concrete structure and new solid phases at the ends of used and new sleepers has been defined. Concrete structure in the middle of the three years old railway sleeper has remained almost unchanged. The obtained results show that technological factors are affecting the deterioration nature of the ends of prestressed concrete sleepers.