DELETERIOUS PROCESSES IN CONCRETE
This article discusses several deleterious processes that affect concrete. Some can be prevented more easily than others, and all of them can be limited considerably by careful design. With steel-reinforced concrete, the commonest cause of deterioration is corrosion of the steel, causing spalling of the overlying concrete. When concrete is first placed, steel is protected from corrosion by the high alkalinity of the cement paste, which prevents corrosion. Such protection is known as 'passivity', but it is removed if the steel is then 'depassivated'. Depassivation is caused mainly by: (1) the influence of chloride ions; and (2) the reduction of alkalinity due to carbonation. In each case, it may be removed by careful concrete specification. Alkali silica reaction (asr), sulphate attack, and acid attack directly affect the chemistry of the concrete; the concrete's susceptibility to such attacks depends on its permability. For asr to occur, alkali, water, and susceptible aggregate must all be present. Sulphate attack occurs when sulphate ions react with aluminates from cement. In industrial environments, the most common acids to attack concrete are sulphuric acid and carbonic dioxide.
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Availability:
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Corporate Authors:
THE CONCRETE SOCIETY
112 WINDSOR ROAD
SLOUGH, BERKSHIRE United Kingdom SL1 2JA -
Authors:
- Harrison, A
- Publication Date: 1995
Language
- English
Media Info
- Pagination: p. 13-4
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Serial:
- CONCRETE
- Volume: 29
- Issue Number: 6
- Publisher: THE CONCRETE SOCIETY
- ISSN: 0010-5317
Subject/Index Terms
- TRT Terms: Alkali; Carbon dioxide; Carbonates; Cement; Concrete; Corrosion; Deterioration; Freeze thaw durability; Halides; Loss and damage; Prevention; Reinforced concrete; Spalling; Steel; Sulfates; Sulfuric acid
- Uncontrolled Terms: Cold
- ITRD Terms: 7353: Alkali; 7393: Carbon dioxide; 7312: Carbonate; 4758: Cement; 9116: Cold; 4755: Concrete; 5252: Corrosion; 1614: Damage; 5255: Deterioration; 2577: Freezing thawing cycle; 7314: Halide; 9149: Prevention; 4794: Reinforced concrete; 5231: Spalling; 4542: Steel; 7310: Sulphate; 7370: Sulphuric acid
- Subject Areas: Security and Emergencies;
Filing Info
- Accession Number: 00720776
- Record Type: Publication
- Source Agency: Transport Research Laboratory
- Files: ITRD
- Created Date: May 24 1996 12:00AM