Investigation on seawater freeze-thaw damage deterioration of marine concrete structures in cold regions from multi-scale

Influenced by the periodic tidal movement, the deterioration environment composed of the tide, seawater, air temperature (freezing) and sea temperature (melting) has become the key to the degradation of the marine reinforced concrete (RC) structures in cold regions. In view of this, the freeze-thaw cycles (FTCs) test of RC structures was carried out, and the damage distribution of concrete with seawater FTCs was tested. Subsequently, based on the temperature distribution, pore water crystallization law and critical saturation of concrete under seawater FTCs, the calculation method of FTCs damage was established from multi-scale, which the calculation results can well reflect the damage behavior of specimens with seawater FTCs. It is significant for the stiffness degradation of specimens with fewer FTCs, and the strength begins to decay for specimens with more than 50 FTCs. Moreover, there is an obvious FTCs boundary for concrete with 50 FTCs, and the depth of the FTCs boundary is close to the limit for RC specimens with 75 FTCs. Based on the discussion of the effects on FTCs, the influence of temperature distribution is much higher than that of critical saturation.