Durability of concrete in supporting structures of the contact network of electrified railways

Abstract

On electrified railways, prestressed centrifuged reinforced concrete poles are widely used as overhead contact system supports. Despite their high‐strength concrete, some poles develop cracks and reinforcement corrosion after several years. Field and laboratory investigations on railways in Ukraine and Azerbaijan revealed no ASR corrosion. The underground section is subject to electrocorrosion on direct‐current lines; in the above‐ground section, atmospheric CO ₂ carbonation progresses as a front. Upon reaching the reinforcement, this front triggers corrosion, leading to cracking and cross‐section loss. Thermodynamic analysis showed that carbonation proceeds via CO ₂ dissolution, with front kinetics governed by diffusion through pore moisture; a kinetic equation is proposed. Concrete reactivity toward carbonation is governed by the volume of water‐accessible pores; a new equation for its determination is proposed. Effective CO ₂ diffusion coefficients and kinetic relationships of front progression were established from experimental and field data. Statistical analysis identified concrete cover thickness scatter as the dominant factor governing pole durability. The minimum cover ensuring the standard service life (e.g., 50 years) was established.