Influence of Controlled Permeability Formwork on the Permeability of Concrete

Corrosion of steel reinforcement related to the intrusion of chloride ion is still the main threats to the durability of concrete structure, especially in marine environment. For the purpose of delaying the Cl⁻ concentration at the surface of steel reinforcement reaching the critical value leading to initial corrosion, the permeability of concrete is usually improved by optimizing the concrete mixture to achieve high compatibility as well as optimized pore structure. In recent years, controlled permeability formwork (CPF) which was originally developed to obtain much smoother surface of the concrete proves to promote the service performance of the concrete by enhancing the surface layer which could protect the structure from Cl⁻ further. In this paper, influence of the CPF on the permeability of concrete was studied with different water to binder ratio, fluidity, and fly ash content. Furthermore, mathematical models were established to discuss the influence on the permeability of the concrete and service life of the structure.