Durability of concrete and reinforcement corrosion in concrete bridge decks and parking structures.

摘要

The deterioration of concrete can be due to: (1) the corrosion of reinforcement; (2) freezing and thawing, including frost damage; (3) chloride ingress; (4) carbonation of concrete; (5) sulphate attack; (6) acid attack; (7) alkali attack; (8) alkali - aggregate reaction; (9) salt attack; and (10) abrasion. Investigation of the durability of concrete generally consists of either the causes of deterioration or the extent of it. Usually, methods used to improve the durability of concrete aim to prevent the causes of deterioration; however, occasionally methods that limit the extent of damage are employed. In this context, and in order to propose test, which can assess the durability between the material properties and deterioration mechanisms, is carried out. Such an analysis should help to focus the attention of various investigators the key issues that ultimately determine the durability of concrete structures.;Corrosion of steel reinforcement in concrete bridge decks and parking structures is one of the most common types of deterioration, which has substantially reduced the useful life of such facilities. This widespread problem and the rapidly increasing cost of maintenance and repair have resulted in great economic and social repercussions. The rising rate of the use of chloride deicing salt is a major factor causing corrosion, and there is no feasible economic alternative to its use at present.;Corrosion may occupy a greater volume than the parent steel reinforcement, thereby extending pressure on the upper concrete, causing it to spall off the main body of concrete. Common types of deterioration and corrosion mechanisms of reinforcement in concrete are reviewed with the view of effects of the concrete environment on the process. It is feasible to study the effect of the individual and combined causes on the onset and rate of reinforcement corrosion.;The role of concrete design and construction practices is discussed as the first protection resort available against corrosion. The importance of concrete quality in providing protection to reinforcement cannot be overemphasized. Bleeding of concrete, which may happen during construction, can result in unfavorable consequences and lead to unfavorable consequences and also to premature corrosion of steel.;Concerning the various deterioration mechanisms described above, one of the fundamental properties that influences the initiation and extent of damage of concrete is corrosion of reinforcement in the concrete structure. Environmental effects such as the freezing and thawing cycles have caused deterioration of the bridge decks and all other exposed reinforced concrete structures. Concrete is full of microcracks even when it is not loaded. When under vehicular traffic, some structural cracks form that can join the other already existing cracks, providing an easy route to reinforcing steel for the deicing salt. The presence of shrinkage and temperature cracks can also do the same. When chloride ions along with moisture reach the level of reinforcing steel, they start corroding the steel reinforcement.;The limitations and applicabilities of the various repair techniques and protective measures in existing structures, of course, have differential impacts on concrete in version environments. Cathodic protection is considered the most versatile and effective means of controlling the corrosion of steel and subsequent deterioration of the concrete.