All the factors which directly or indirectly contribute to the corrosion of reinforcement can be listed as follows:
(a) Presence of cracks in concrete,
(b) Permeability of concrete,
(d) Formation of corrosion (galvanic) cells,
(e) Use of calcium chloride as accelerator,
(f) Presence of soluble sulphates,
(g) Alkali-aggregate reaction,
(h) Presence of moisture,
(i) Ingress of sea water into pores of concrete,
(j) Inadequacy of cover to reinforcement, and
(k) Impurities in mixing and curing water.
Hence to save reinf. From corrosion, there are two basic approaches-
(1) Stopping of moisture entry to reinf.
(2) Protection of alkaline environment
This can be brought about by the following measures:
(1) Adequate cover to reinf.
(2) Good quality dense concrete with least permeability and porosity and without any cracks. This can be obtained by proper proportioning, mixing, compacting and curing of concrete and by using less w/c ratio and taking necessary precautions to avoid cracking.
(3) Protection of alkaline environment by saving it from attack carbonation and chlorides.
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