Materials and fire Flashcards
Timber is a combustible material, what does this mean?
It will burn
Under a sustained fire, what happens to timber?
It develops a charred layer which slows the penetration of heat
Why are fire retardants used?
Surface treatments which help reduce the spread of fire but are not combustible.
As masonry units are non-combustible, what does this mean?
They will not burn in a fire
Describe what happens to masonry walls in the case of a fire:
-Subject is heated to one face, giving rise to a thermal gradient on the wall face
-Thermal stresses will be induced, resulting in deflection of the wall,#
-As long as the extent of the deflection is less than the wall’s thickness, failure is unlikely.
In a general fire, what 4 things increase the fire resistance of masonry?
Wall thickness, higher thermal resistance, an increase in water content, the addition of non-combustible wall finishes
At what temperature does steel start to lose its strength?
400 degrees
How is structural steel protected in a fire?
Through the use of insulating materials, spray, broading and paint coating etc.
What is the main difference between the behaviour of concrete and steel in a fire?
Concrete is not as conductive as steel
What temperature does concrete start to lose its strength?
350 degrees
Concrete is non-combustible, what does this mean?
It does not burn
Why is there slow rates of temperature increase across a concrete section?
Concrete has high thermal inertia, which helps keep the steel reinforcement low to avoid weakening of the steel.
What do the thermal and mechanical properties of concrete depend on?
The aggregate type, cement mix and water content.
What is the most important safety factor in the fire performance of reinforced concrete elements?
Sufficient concrete cover to the steel bars
What happens to FRP in a fire?
Weaken and lose strength above a certain temp
