The effects fire has on concrete are complex and can vary from negligible or merely cosmetic damage to rather fundamental structural issues that can require specialists in concrete repair to fix.
In some cases, such as the work we did on Secklow Gate Bridge in Milton Keynes, the intensity of the fire was such that major complex structural works were required to fix it.
As Milton Keynes City Council noted in a statement to BBC News, there are very few companies capable of undertaking this kind of complex concrete repair, but to understand why, we need to briefly explain how fire affects concrete in different ways.
Fire is often characterised as being highly fire-resistant, which is only true in the sense that it does not set alight and will not burn in most circumstances.
However, prolonged exposure to fire and the intense heat that it radiates can cause severe thermal degradation to the concrete, which not only includes more superficial issues such as oxidation-induced colour changes and spalling, but also cracking and the loss of compressive strength.
This strength loss is the biggest concern given the primary use of concrete as a primarily structural material, and exactly how much harm is caused will vary depending on the intensity of the heat and the duration to which it is exposed.
A small fire that is largely contained will often have relatively minimal effects, but the longer and more intense the conflagration, the more long-term foundational damage will be caused.
Repair is still possible in all but the most dire of circumstances, but the more fire damage that is caused, the more complex the repair and the more likely you will need to use more specialist repair methods following careful analysis of the structure in question.
This often involves the use of additional reinforcing materials such as carbon fibre, careful removal of parts of the concrete that are beyond repair using tools such as hydro demolition, and restoration using sprayed concrete to match the shade and texture of the original concrete.