The Marine Environment, The High-performance Concrete Resistance To Chloride Ion Erosion Performance

High performance concrete (HPC) is one of new building materials. Due to its excellent properties, such as high workability, high strength and high durability it is widely used in civil engineering.However, the resistance against the chloride ion induced corrosion is an important topic for structures in marine environment.Ordinary concrete can be in use in marine environment for 40 to 50 years, while the service life of HPC structures can be over one hundred years. This indicates much lower maintenance cost and the reduction in environmental pollution caused by concrete destruction.The diffusion of chloride ion in concrete takes place through cracks, defects and pores in concrete.In the present paper the ability of HPC to resist the chloride ion induced corrosion has been determined. The relationship between the concrete microstructure and the chloride ion penetration in concrete, as well as the influences of raw materials and mixing proportions on the microstructure of HPC have been investigated and analyzed.The HPC in this paper belongs to the class C60. It is composed of Portland cement, mineral and chemical admixtures. To simulate the real application conditions specimens were cured in real marine environment and loaded as in practice application. The influences of water to binder ratio, the quality and content of fly ash, the ratio between ground granulated blastfurnace slag (GGBS) and fly ash, the superplasticizer and the sand ratio on the properties of fresh and hardened HPC have been determined. Based on the experiment results an optimal mixing proportion for HPC has been obtained.In the research the HPC contained 0.01% air entraining agent and 1.2% superplasticizer (in cement weight). The slump reached 20 cm and the strength was higher than the reference mixture. Even 40% cement was replaced by mineral admixtures, i.e. 25% by fly ash and 15% by GGBS, the strength can fill the requirement.In the experiments the content of air entraining agent in concretes was constant at 0.01% of the cement weight. The water-binder ratio, the superplasticizer and the sand ratio were varied to determine their influence on the properties of concrete. Totally 9 mixtures were tested. The concrete properties tested in the experiment were workability, strength and the permeability, especially the permeability of the concrete which was cured and loaded as the structures in real application. The influence magnitude and sequence of above mentioned factors was defined. In the best mixture the water-binder ratio is 0.36, cement, GGBS and fly ash 320 and 90 and 150, respectively, superplasticizer 1.4% and sand ratio 0.33.Moreover,the waterproof performance of concrete in seawater shows that the permeating depth is less than 2 cm and the waterproof performance increases over 50% if the concrete's surface is dipped by waterproof dope.