fire resistance concrete

2. Respected Sir;
Sohail Abassi Sahb
Subject Teacher;

3. Khalil ur Rehman
L-14CE-55

4. Fire resistance of concrete
and
Effects of fire on concrete strength

5.  It is vital that buildings and structures are
capable of protecting people and property
against the hazards of fire: concrete has a
major role to play in this
 In most cases, concrete does not require any
additional protection because It is non-
combustible (i.e. it does not burn) and has a
slow rate of heat transfer, which makes it a
highly effective barrier to the spread of fire.

6.  Concrete does not burn – it cannot be ‘set on
fire’ like other materials in a building and it
does not emit any toxic fumes when affected
by fire
 The rate of increase of temperature through
the cross section of a concrete element is
relatively slow and so internal zones do not
reach the same high temperatures as a
surface exposed to flames

7.  Concrete has low thermal conductivity
For This Reason
Concrete is much better fire resistant
material than Steel,
Steel heats rapidly and its strength drop
appreciably in short time but a Temperature
below 250c has no effect on concrete
structure

8.  This excellent performance of concrete is due
to the main concrete constituent materials
(i.e. cement and aggregates) which, when
chemically combined within concrete, form a
material that is essentially inert.

9.  calcium hydroxide in cement is of a great
importance to resist a high temperature.
Cements which release the least amounts of
calcium hydroxide during hydration and
hardening of the concrete are certainly to be
favored.

10.  Studies of concrete heated to high
temperature indicate that what's type of
aggregate is used in the concrete paste,
 It seems obvious that aggregates with low
coefficients of thermal expansion in the range
of temperature that the concrete is expected
to experience would be preferable.

11.  Thermal expansion of an aggregates depends
upon % amount of silica contents
 Higher will be the amount of silica content in
the aggregates higher will be its thermal
expansion and so it will be not suitable for
concrete to with stand with higher
temperature.

12.  The first effects of a temperature rise in
concrete will occur between 200 and 400
degrees Fahrenheit, Because
Evaporation of the free moisture contained in
the concrete mass occurs between this
temperature.
 As the temperature approaches 500 degrees
Fahrenheit , dehydration or loss of the non
evaporable water or water of hydration,
begins to take place.

13.  At 600 degrees Fahrenheit strength
reduction would be in the range of 15 to 40
percent.
 At 1,000 degrees Fahrenheit reduction in
compressive strength would typically range
from 55 to 80 percent of its original value.
because calcium hydroxide dehydrates at that
temperature.

14.  Aggregates also begin to deteriorate at about
1000 degrees Fahrenheit; for example, quartz
expands greatly and suddenly at 1063
degrees Fahrenheit.