chapter  2
Degradation of reinforced concrete structures
Pages 68

Concrete is the most widely used construction material in the world, up to 10 billion tons per year worldwide consumption. Deterioration of concrete structure has become a world-wide problem and a huge burden on human society and the economy. For instance, in the UK, £500m is spent on concrete repair per year. In the USA, US$300-400m dollars are needed for the renovation of bridges and car parks alone where de-icing slats are commonly used in practice and cause severe concrete deterioration and steel corrosion. In China, the annual economic loss due to corrosion in concrete structures has reached 100 billion RMB. Deterioration is any adverse change of normal, mechanical, physical, and chemical properties either in the surface or in the body of concrete, generally due to the disintegration of its components. Degradation processes of concrete usually start from the materials level and then proceed to the structural level. They can be classified as physical (caused by natural thermal variations such as freeze-thaw cycles) artificial (such as those produced by fires), or by natural disasters (such as earthquakes and typhoon), by abrasion (erosion), chemical (attack by acids, sulfates, ammonium and magnesium ions, pure water, salts or alkali-aggregate reactions), biological (fouling, biogenic attack), and mechanical (impact, explosion, overloading, settlement, cyclic loading) (Bertolini et al. 2004).