Article
based on contribution by: Mr Saransh
Kataria & Mr Satyajeet
Harne , Civil
engineering Students, S.G.S.I.T.S, Indore
Spalling
can be described as the breaking of
layers or pieces of concrete from the
surface of a structural element when it is exposed to the high and
rapidly
rising temperatures experienced in fires.
Mechanisms
of Spalling:
Phenomena
of Spalling is caused through different
mechanisms of Spalling as given below:
Pore
pressure rises due to evaporating water when the temperature rises;
Compression
of the heated surface due to a thermal gradient in the cross
section;
Internal
cracking due to difference in thermal expansion between aggregate
and cement paste;
Cracking
due to difference in thermal expansion/deformation between concrete
and reinforcement bars;
Strength
loss due to chemical transitions during heating.
Different
mechanisms (as above) give rise to different types of spalling as
tabulated
below:-
Violent
Spalling
Sloughing
off
Corner
Spalling
Explosive
Spalling
Post
Cooling Spalling
Pore
Pressure due to
evaporation of moisture
x
x
Compression
of the heated
surface due to a thermal gradient in the cross section
x
x
Internal
cracking due to
difference in thermal expansion between aggregate and cement paste
x
x
x
Cracking
due to difference
in thermal expansion/deformation between concrete and reinforcement
bars
x
Strength
loss due to
chemical transitions during heating
References: 1.
"Fire
Performance of High-Strength
Concrete Structural Members"
by V.K.R.Kodur 2.
"The
effect of fire-Concrete
Spalling" from
http://www.promat-tunnel.com
