Corrosion-Induced Degradation of Marine Reinforced Concrete Structures: Case Studies from Polish Ports and Implemented Repair Methods

Most marine hydraulic structures, such as breakwaters, quay walls, and piers, operate both above and below the water surface throughout their service life. Maintaining, modernising, or reinforcing these concrete and reinforced concrete structures, which are in constant contact with seawater, poses a significant engineering challenge. Ensuring structural performance and operational continuity during repair work is particularly demanding. This study identifies the main types of environmental impact and the associated mechanisms of concrete degradation in marine infrastructure, including chemical, physical, and mechanical interactions that accelerate deterioration. Documented examples of corrosion damage observed in harbour breakwaters, quay walls, and pier structures are presented, along with proposed repair strategies and their practical implementation. Photographic documentation illustrates the extent of damage, repair processes, and the final condition of the renovated elements. The paper focuses on selected case studies of repair and strengthening works carried out on marine reinforced concrete structures exposed to the aggressive conditions of the Baltic Sea. The analysed facilities are located in Polish ports along the Gulf of Gdańsk, with the exact location of each provided in the respective case description. Each case study includes a detailed account of the applied repair technologies, ranging from surface reprofiling and polymer-cement coatings to low-pressure crack injection, prefabricated GRC elements, and CFRP strengthening systems. The findings demonstrate that accurate diagnosis of deterioration processes, combined with repair strategies tailored to the specific structural type and extent of damage, can effectively mitigate corrosion, restore structural and operational capacity, and significantly extend the service life of port infrastructure.