RCC or Reinforced Cement Concrete is an integral part of a building. The strength and durability of any building are dependent on the right mix of concrete and other binding agents. Concrete, being a poor thermal conductor is ideal as heat does not impact or deteriorate it for a long time.
But, unprecedented calamities or incidents are inevitable. Though, concrete bears the brunt of heat effectively, fire damage mechanism is one thing that can result in its deterioration leading to the collapse of a building in some cases.
When a building gets ablaze the cement structure does not get much affected at once; the stagnation happens over time.
The mechanism of fire on an RCC structure (which also includes cement gel, aggregate, other reinforcement material, and moisture) can be extremely damaging for its durability.
Any structure which has been under a fire incident require to be reinstated before getting opened for any commercial or residential use.
Here, we are trying to explain the damage, fire can do to a concrete structure and how can we identify the same in order to calculate the reinforcement work a structure requires;
For ages, concrete has been voted as the best building material as heat does not put any adverse effect on it for a long time.
However, extreme heat can lead to expansion and further cracking of cement leading to the breakdown of the RCC structure.
Fire damage mechanism- Concrete can easily bear the environmental heat as it also has the capacity to cool down quickly, the heat is not constant and therefore does not impact the structure at once.
In a fire, however, the temperature increases strikingly and can cause long-term damage not only to the outer layer of a cement structure but the inner materials, which are used as a binding force, as well.
The temperature of a fire (in a building) can rise rapidly from 200 degrees Fahrenheit to more than 1000 degrees Fahrenheit.
Any RCC structure, which has the capability of easily bear heat up to 200 degrees Fahrenheit. Any temperature above that can jeopardize the strength of a structure.
The visible signs are the cracks that form after a fire has been doused or the discoloration of the cement.
Cement cools down quickly, therefore, the ramification of fire at different temperatures is different and can be bifurcated at different levels;
|Temperature (in Fahrenheit)||Plausible Impact|
|200-400||A continuous fire can result in spalling or crack-down of the outer layer of cement.|
|400-600||At this temperature, the RCC structure begins losing its load-bearing capacity.|
|Above 700||A fire can reach up to a temperature of 1200 degrees if not controlled which can be adversely damaging for a structure.|
Cement is known to be a non-combustible material. However, in the case of a fire damage mechanism, cement, begins to expand resulting in fissures that expose the inner material like steel, moisture, and other binding agents which are susceptible to fire.
In extreme heat, moisture evaporates quickly leading creating cracks in the outer layer and heating the inner layer as well.
Cement, as per its nature, cools down quickly and when the cooling agent is forced upon fire the outer layer of cement cools quickly while the inner layer takes time to cool down.
The variation in temperature further leads to the deterioration of the structure. Also, other materials in a structure which are damaged do not get reinstated on their own.