Protection of Concrete and Steel Reinforcement from Deterioration under the Effect of Corrosive Marine Environment

Abstract

The national strategic plan for population re-distribution in Egypt supports the establishment of new towns and urban settlements across the coastal zones (as well as vacant desert lands) to relieve the pressure on the packed Nile Valley and Delta and to encourage internal migration to new urban coastal communities. The North – Western coast and the Eastern coast regions are expected to absorb huge ratio of the population during the coming years due to development in the touristic, residential and industrial projects as well as the oil petrochemicals natural gas and offshore industries in these areas. [Particularly after delineation of the maritime boundaries between Egypt and neighbouring countries]. Since reinforced concrete has a poor service record in these areas, great demands should be undertaken in terms of durability, safety and prevention of damage for the used reinforced concrete during its service life in these areas. A considerable amount of research has been carried out, and is still continuing, with the intent of finding additives and techniques for modifying the concrete to reduce its vulnerability to attack. Also, variable means have been adopted to protect the steel reinforcement from the attack of penetrating aggressive elements from the surrounding hostile marine media. An overwhelming opinion is that: the principal cause of concrete deterioration in marine environment is due to the ingress of chloride ions causing corrosion of steel reinforcement leading to cracking and spalling of concrete. In such situation, it used to be thought that , using sulfate resisting cement (SRC) (C3A ~ 3.5%) would provide adequate protection against sulfate attack, but, would fail to remove free chlorides. Therefore, several researchers recommended using ordinary portland cement (OPC) (having higher C3A content) as it would resist the chloride attack on concrete as well as the chloride – induced reinforcement corrosion by combining a considerable part of chloride into a calcium chlorioaluminate compound. In addition, if that cement is modified with a suitable admixture (e.g. SF), it could provide, to a certain extent, sulfate resistance.