Marine and salt-exposed structures such as ports and bridges were early to demonstrate that concrete had an inherent durability ''flaw", In many countries, ''low-permeability'' and "low diffusion'' concrete has been used for marine and salt exposed structures since the mid-eighties. But the extension in "time-to-corrosion" and time to maintenance of these structures has often been disappointingly short of expectation. The problem is, even very dense concrete is still "absorptive''. It still sucks.The primary mechanism of the penetration of moistures and chlorides etc. enter into concrete is now known to be "absorption"; and the speed of this penetration by absorption is much greater than penetration by pressure permeability-in fact it has been confirmed to be a "million'' times faster than by permeability: long-term research by the (UK Govt.) Transport Research Laboratory (UK) identifies "capillary absorption'' as the dominant water and salt transport mechanism in high quality, low permeability bridge structures concrete, and discusses use of absorption-based specifications for ensuring concrete durability.In order to achieve a design life durability for structural concrete, especially in the field of marine concrete, is to adopt the "ultra low absorption'' with "Hydrophobic Pore-blocking Ingredient'' concrete that having the longest independently-confirmed and verified field performance history in the world in deliver the truly long term durable and corrosion free concrete.
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