Civil Engineering Reference
In-Depth Information
In the UK the effects of freeze-thaw damage are usually limited to several
centimetres depth, but in some places the effects of freeze-thaw damage may
penetrate to several tens of centimetres. Petrographic examination can be
used to measure the depth of deteriorated concrete and establish the depth
of concrete to be removed prior to repair. The repair material needs to be
resistant to moisture penetration and it is particularly important that the
repair/substrate contact is sound with no potential for moisture build up.
In some parts of the UK, aggregates susceptible to drying shrinkage may
exacerbate the effects of freeze-thaw damage.
Frost damage strictly refers to damage to concrete when it freezes during
the setting process and as such should not be confused with freeze-thaw
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magnification to illustrate the development of microcracking in a concrete sample
affected by fire damage. The external surface is visible along the right side of the field
of view. Note the development of surface-parallel microcracks that pass through both
the coarse aggregate particles and the surrounding paste. The paste towards the inner
end of the sample has a patchy, moderate to low porosity.
Figure 2.9
Photomicrograph of a thin section taken at a depth of about 2 mm below
and is substantially weakened. The level of damage seen in the section of this part of
the sample is consistent with temperatures in excess of 300°C.
