The 21st century is known as the "century of the ocean". The development of ocean resources cannot do without the demand for marine engineering construction. Due to the special water vapor environment of the ocean, the concrete in the splash zone of the constructed marine engineering will be severely corroded, affecting the service life of marine engineering. In order to improve the service life of marine engineering, the commonly used method is to brush anti-corrosion coating on the surface of the splash zone of the marine engineering that has been poured. This has a certain effect on anti-corrosion of marine engineering, but the effect is limited. Some universities have jointly developed a repair/protection material using Sulphoaluminate cement, which can improve the corrosion resistance of marine engineering fundamentally from the perspective of material properties.
The cement used in marine engineering construction is also called special cement, which is a kind of cement that has more prominent functional properties than ordinary cement in a certain aspect. Compared with ordinary cement, marine cement needs to have stronger ability to resist chloride ion corrosion in water, and the density also has different requirements. The mineral composition of cement clinker, the comprehensive utilization of blended materials, and the cost of production and research and development are all necessary factors to consider for the preparation of high-quality marine cement.
Sulphoaluminate cement has remarkable ability to bind chloride ions. With the decrease of the water-cement ratio of Sulphoaluminate cement, its ability to bind chloride ions will be significantly enhanced, making its ability to resist chloride ion erosion stronger. The age and variety of Sulphoaluminate cement are also important factors that affect the diffusion performance of chloride ions in concrete. Therefore, Sulphoaluminate cement is a good solidifying adhesive material for chloride ions, and can effectively restrict the diffusion of chloride ions inside concrete through physical and chemical actions. And through this characteristic, it can effectively improve the microstructure inside concrete, enhance the structural strength of the interface between the substrate and the adhesive material, increase the distortion degree of the ion transmission path, and increase the ion diffusion coefficient as the water-cement ratio increases.
When the marine Sulphoaluminate cement works in seawater, due to the fact that seawater can provide a large amount of SO42-, these Sulphoaluminate ions will inhibit the transformation of three-sulfur type hydrated Sulphoaluminate calcium (AFt) into single sulphur type hydrated Sulphoaluminate calcium (AFm), thus causing an increase in the structure water of AFt and a decrease in density, making its crystal structure grow more fully. As Sulphoaluminate ions can replace chloride ions in Ca-Al hydrocalumite and generate Aft, chloride ions also affect the stability of AFt, generating a chemical balance between the two under certain conditions. The content of AFm is very small in the structure of slurry, so the damage degree to the structure of slurry caused by the transformation of AFm from Ca-Al hydrocalumite in the structure of slurry is very low.
