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Assessing Fire Damage

Concrete affected by fire can be substantially weakened. Fire damage often generates cracks that are parallel with external surfaces and measurements of compressive strength may not reflect weakening of concrete as a result of fire. Using petrography it is possible to determine the depth of damaged concrete make an assessment of the original quality of the concrete. At Geomaterials, petrographic measurements are interpreted following the latest guidance in Concrete Society Technical Report No. 32. Using petrographic techniques it is generally possible to establish the following types of information.

  • The depth/temperature profile
  • The depth of the 300°C isotherm
  • The maximum depth of weakening of the cement paste from the porosity and microcrack distribution
  • The depth of transition from sound to damaged concrete

The following photographs illustrate some of the forms of fire damaged that can be recognised through petrographic examination.