Civil Engineering Reference
In-Depth Information
C
RACKING
< 300°C Boundary cracking alone
300-500°C Serious cracking in paste
500°C
Change to anisotropic paste
The depth of colour change is often a good guide to the overall depth of
damage. This may often be no more than a few mm for short-duration fires,
even if high temperatures are reached at the surface. As a general rule, if no
spalling has occurred, no damage is likely to have occurred to the steel. (This
does not apply to pre-stressed or post-tensioned concrete, which requires
specialist assessment.) A structural engineer should always be involved in
assessment of any repair, including fire damage.
Poor-quality construction
During construction, lack of attention to proper quality control can produce
concrete which may be inferior in both durability and strength to that
assumed by the designer. Particular factors in this respect are compaction,
curing conditions, low cement content, incorrect aggregate grading, incorrect
water/cement ratio and inadequate cover to reinforcement.
