Durability of reinforced concrete in the coastal zone of the Far Eastern Federal District

Abstract

The article examines the durability of reinforced concrete structures in the coastal zone of the Far Eastern Federal District under the combined effects of marine salt aggression and cyclic temperature transitions through 0 °C, leading to frost damage and accelerated reinforcement corrosion. It is shown that under alternating wetting and drying, chloride mass transfer is intensified by capillary suction, while chemical interactions with seawater ions reduce the alkalinity of the cement paste and accelerate steel depassivation. Based on long-term field observations and laboratory tests (depth-wise chloride profiles, microstructural analysis, ultrasonic assessment of the dynamic modulus of elasticity, and corrosion potential mapping), the nonlinearity of degradation processes and a pronounced synergism are identified: microcracks induced by frost action form channels for accelerated salt ingress, while salt crystallization increases internal stresses. Quantitative data demonstrate the critical role of elevated water-to-cement ratio and small cover thickness, as well as a sharp dependence of resistance on aggregate type: limestone aggregate causes the greatest loss of stiffness, whereas basalt provides substantially more stable behavior. It is established that densification of the matrix with active mineral additives significantly reduces chloride permeability and shifts the time to reaching hazardous electrochemical potentials. The presented results make it possible to assess the relevance of proposed materials and structural solutions for infrastructure facilities in the coastal zone of the Far Eastern Federal District and to refine predictions of residual service life under conditions of nonstationary moisture transport.