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Typical crack pattern of the alkali-silica reaction (ASR). The gel exudations through the concrete cracks have a characteristic yellow color and a high pH. The fatty aspect of the exudations imbibing the concrete porosity along the cracks is also a distinctive feature of ASR. The alkali-silica reaction as a chemical cycle process
Instead of using a 'nominal mix' of 1 part cement, 2 parts sand, and 4 parts aggregate, a civil engineer will custom-design a concrete mix to exactly meet the requirements of the site and conditions, setting material ratios and often designing an admixture package to fine-tune the properties or increase the performance envelope of the mix ...
A fairly well-defined reaction front can often be observed in thin sections; ahead of the front the concrete is normal, or near normal. Behind the reaction front, the composition and the microstructure of concrete are modified. These changes may vary in type or severity but commonly include: Extensive cracking; Expansion
When a reinforced concrete member is put in tension, after cracking, the member elongates by widening of cracks and by formation of new cracks. Figure 1 Formation of internal cracks. Ignoring the small elastic strain in the concrete between the cracks, we can relate the crack width to the strain of the member by:
Flow table with a grip and a hinge, 70 centimetres (28 in) square. In the American version of this test, the table is 10 inches (25 cm) diameter per ASTM C 230.; Abrams cone, open at the top and at the bottom - 30 centimetres (12 in) high, 17 centimetres (6.7 in) top diameter, 25 centimetres (9.8 in) base diameter.
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mild steel cracks in the presence of alkali (e.g. boiler cracking and caustic stress corrosion cracking) and nitrates; copper alloys crack in ammoniacal solutions (season cracking); high-tensile steels have been known to crack in an unexpectedly brittle manner in a whole variety of aqueous environments, especially when chlorides are present.
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