Stainless Steel in Concrete (EFC 18) PDF

Introduction

In reinforced concrete structures the concrete guarantees chemical and physical corrosion protection of the unalloyed reinforcement. Thus, the alkaline electrolyte of the pores passivates the steel and the concrete - as a more or less dense (fine porous) material - keeps corrosion-promoting substances away from the reinforcement, that is, if a sufficient depth of concrete cover is provided. In general, steel in concrete is adequately protected against corrosion.

However, despite these protective mechanisms, corrosion of reinforcement can occur. This can result either from the carbonation of the concrete or from the effect of chloride ions if oxygen and moisture are also available. Chloride ions may penetrate into hardened concrete of structures exposed to marine environments or to de-icing salts.

As a result of the corrosion reaction rust forms and occupies a volume greater than that of the original metal. This process can cause cracking and spalling of the concrete leading to further corrosion and a loss of bond between the concrete and the steel. A dangerous situation can then arise where a structural member loses cross-sectional area since there will then be increasing stress on the remaining section which could possibly lead to structural failure.

If corrosion problems persist additional corrosion protection methods such as galvanising, epoxy coatings, inhibitors or cathodic protection must be used. Nevertheless, there are limits to the application of these [1] and more comprehensive solutions need to be developed.

In the world of repair and restoration of structures stainless steel appears to be the metal often used. Typical applications are usually where a sufficient cover cannot be obtained. An increasing amount of this material is also to be found in bridge engineering [2, 3] and stainless steel is generally located at construction joints or critical gaps between columns and decks. Another typical application is in prefabricated wall elements where the reinforcement connects the outer and inner walls. In cases of very corrosive environments stainless steel may also be used in new constructions. Nevertheless, it is not envisaged that stainless steel will replace any really significant part of the massive tonnage of the present carbon steel reinforcement output. The use of higher quality steels, such as austenitic stainless steels, will increase the reliability of multi-storey car park decks and outer stairs which are likely to be contaminated with deicing salts, concrete elements in thermal baths, piers at the sea-coast and plants for the desalination of sea water. Stainless steel is also suitable for the reinforcement in lightweight pre-cast elements.

Edited by: C.L. Page