Fire Damage

Above ~300 °C the calcium hydroxide in hardened concrete begins to break down; above ~500 °C compressive strength is significantly and permanently reduced; and reinforcement loses yield strength that only partially recovers on cooling. A methodical post-fire assessment is essential before an element can be recommissioned.

• 01Building fires, office, residential, industrial
• 02Vehicle fires in car parks
• 03Industrial and process fires
• 04Deliberate acts

• Colour change (pink 300 to 600 °C, whitish-grey 600 to 950 °C) indicating temperature reached
• Spalling, explosive or progressive, exposing reinforcement
• Cracking, particularly along reinforcement lines
• Sooting, softening of surfaces, loss of section

• T · 01Post-fire visual and colour survey to estimate temperature contours
• T · 02Ultrasonic pulse velocity to assess depth of damaged concrete
• T · 03Core sampling for residual compressive strength
• T · 04Cover surveys and reinforcement testing where accessible

Damaged concrete is broken out to sound material, often to a considerable depth. Reinforcement is inspected and, where yield strength is compromised, supplemented or replaced. The element is reinstated in a repair mortar appropriate to the load duty. Where structural capacity is materially reduced, strengthening (plate bonding, FRP wrap or additional bars) is designed in as part of the reinstatement.