concrete structures which are affected by the fire and which are damaged can be retrofitted

1. ASSESSMENT METHOD AND
REHABLITATION TECHNIQUE OF FIRE
AFFECTED CONCRETE STRUCTURE
Presented by:
Mohammed Faazil
Alvas institute of engineering and technology
1

2. Contents:
• Introduction
• Assessment of fire affected structures
• Assessment of non-structural members and utilities
• Assessment of structural members
• Rehabilitation techniques
• Conclusion
• references
Assessment method and Rehabilitation technique of fire
affected concrete structure 2

3. Introduction:
• Concrete is being a heterogeneous material, consisting of cement, aggregates and
steel.
• Each of these components has a different reaction to thermal exposures.
• Concrete during high temperature event has a complex behaviour due to the
differences in coefficient of thermal expansion of each constitute.
• High temperature during fire reduces strength of reinforced concrete structure due to
deformability of materials, reduction in cross-sectional dimensions, weakening of
bond between reinforcement and concrete.
Assessment method and Rehabilitation technique of fire
affected concrete structure 3

4. Assessment of fire affected structures:
• The aim of assessment of fire damaged structure is to propose appropriate repair
methods or to decide whether demolition of elements or the whole structure is more
appropriate.
• The severity of the damage depends upon the duration, magnitude and temperature
attained by fire.
• General assessment involves following steps:
a) Type of structure
b) Scope of damage
c) Size, duration and temperature of fire.
Assessment method and Rehabilitation technique of fire
affected concrete structure 4

5. Assessment of non-structural members and utilities:
• Non-structural members of the building like doors, windows, ventilators, partition
walls, floor coverings etc. bear heavy damages often in case of fire.
• Visual inspection of the building with a team of crafts men can determine the
condition of the utilities or non-structural members.
• There is no need to conduct excessive testing on these parts or utilities of the
building.
Assessment method and Rehabilitation technique of fire
affected concrete structure 5

6. Item Nature of damage
(FD,WD,ID,SD)
Damage rating
(1 to 5)
Description Recommendation
Windows
Doors
Roof coverings
Partition walls
HVAC
Plumbing
Electrical wirings
Railings
Flooring materials
Light fixtures
Alarm system
1 = needs cleaning, 2 = needs surface treatment, 3 = needs minor repair, 4 = needs major repair, 5 = replacement
FD = fire damage, WD = water damage, ID = internal damage, SD = smoke damage 6

7. Assessment of structural members:
• Condition assessment of structural members is very vital part as the strength of
structure is dependent on it.
• For the assessment of structural members following methods are used:
a) Visual inspection
b) Field testing
c) Laboratory testing
Assessment method and Rehabilitation technique of fire
affected concrete structure 7

8. Visual inspection:
• Visual inspection is a very powerful tool and one of the most common and oldest
available non-destructive testing techniques available.
• Visual inspection gives a wealth of information about the structure and its
condition but has certain requirements and limitations.
• Visual inspection only gives impression of visible issues and hidden issues remain
unnoticed.
Assessment method and Rehabilitation technique of fire
affected concrete structure
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9. Field testing:
• After visual inspection, field tests have to be performed to get better understanding
about the structure and its residual strength.
• Location of these field tests have to be carefully decided by an engineer as it has a
very obvious effect on the results.
• Various types of field testing are as follows:
a) Rebound hammer
b) Ultra sonic pulse velocity
c) Windsor probe or penetration resistance test
Assessment method and Rehabilitation technique of fire
affected concrete structure 9

10. a) Rebound hammer:
• A Rebound Hammer is a simple, handy tool used to measure the elastic properties
or compressive strength of concrete or rock, mainly surface hardness and
penetration resistance.
• The values of the test are quite variable even when same test is performed on the
same element at two different places.
Assessment method and Rehabilitation technique of fire
affected concrete structure
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11. b) Ultra sonic pulse velocity:
• This is a commonly used non-destructive test. It is done to assess the quality and
compressive strength of concrete by ultrasonic pulse velocity method.
• The method consists of measuring the time of travel of an ultrasonic pulse
passing through the concrete being tested.
• A complex system of stress waves develops, which include both longitudinal and
shear waves, and propagates through the concrete. 11

12. c) Windsor probe or penetration resistance test:
• Windsor probe or penetration resistance test is used as a non-destructive testing
technique for the evaluation of concrete’s compressive strength.
• Penetration resistance test is not sensitive to the personal skills though probe has
to be at right angle to the testing surface and it is compulsory but doesn’t require
special skills to be carried out.
Assessment method and Rehabilitation technique of fire
affected concrete structure
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13. • Laboratory testing is done for the samples collected from the site.
• Laboratory testing are destructive sampling test.
• The following methods are used for laboratory testing:
a) Petrography
b) Tensile test
c) Scanning electron microscopy
Laboratory testing:
Assessment method and Rehabilitation technique of fire
affected concrete structure 13

14. a) Petrography:
• Petrography test is like putting the structure under microscope.
• Petrography is done on the samples that are obtained from the field by core sampling at
various depths.
• The sample must be extracted with care as it must inhibit the characteristics of the damage
that is needed to be studied.
Assessment method and Rehabilitation technique of fire
affected concrete structure 14

15. b) Tensile test:
• If concrete cover is not thick and spalling of cover has occurred then there are fair
chances that reinforcement bars will be damaged.
• The samples are placed within the grips of the UTM and then they are loaded under
uniform tensile load until failure.
• Tensile Test gives us virtually all necessary information we require about the
reinforcements of the fire damaged concrete structure. 15

16. c) Scanning electron microscopy:
• SEM test is conducted on the damaged reinforcement specimens to understand the
patterns of the material fibre, which gives valuable information about the stress in
the reinforcement bars.
• This is pretty helpful in term to understand the overall stability and integrity of
pre-stressed concrete elements.
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affected concrete structure 16

17. • For fire damaged building not many options are available for retrofitting of
structure.
• Most conventional ones are strengthening of structural members with fibre
reinforced plastic and replacement of damaged concrete either with shotcrete or
in-situ placement of concrete.
• Following are the methods of rehabilitation:
a) Fibre reinforced polymer
b) Concrete jacketing
c) Steel jacketing
Rehabilitation techniques:
Assessment method and Rehabilitation technique of fire
affected concrete structure 17

18. a) Fibre reinforced polymer:
• Fibre reinforced polymer is a synthetic material in which polymer matrix is reinforced
with fibres.
• FRP is highly durable material if properly handled. It is a non-corrosive material hence
not suspected to oxidation like steel.
• FRP material doesn’t require special labour effort as it can be easily moulded into shapes
and can cover almost all geometries of buildings without any formwork requirement.
Assessment method and Rehabilitation technique of fire
affected concrete structure 18

19. b) Concrete jacketing:
• Concrete jacketing is the retrofitting technique for structural members. In fire
damaged building concrete jacketing can provide extra strength to damaged
structural member.
• Concrete jacketing can be done on column and beams and slab systems as well.
Assessment method and Rehabilitation technique of fire
affected concrete structure 19

20. • It is done by removing the existing cover of the element and providing a new
concrete cover along with new reinforcement bars.
• The new applied concrete jackets the existing structural element and provides much
needed strength after the structure is damaged.
• Concrete jacketing can be done on column and beams and slab systems as well.
Assessment method and Rehabilitation technique of fire
affected concrete structure 20

21. c) Steel jacketing:
• Steel jacketing is the technique in which structural element is encased by steel angles,
channels and bands.
• This technique gives certain confinement to the element and helps to increase its flexural
strength.
Assessment method and Rehabilitation technique of fire
affected concrete structure 21

22. • As steel will be exposed to the weathering agents hence it is mandatory to apply
protective coating against rust.
• Steel is a green material as it doesn’t depletes fossil fuel and waste too much
energy in its manufacturing as it is in case of FRP. Hence it can be credited as a
sustainable repair technique.
• It is pretty fast as unlike concrete jacketing it doesn’t need long curing times and
number of activities are also reduced.
Assessment method and Rehabilitation technique of fire
affected concrete structure 22

23. Conclusion:
• All structures subjected to fire should be evaluated in a systematic manner to determine
the extent of required repairs
• The intensity and duration of the fire can be estimated by observing the collateral
damage
• Evaluations combined with an engineering analysis, allow effective and economical
repair details to be developed and installed as needed.
• Assessment helps in reducing construction costs and preventing unnecessary
constructions
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affected concrete structure 23

24. References:
[1]. Ankit M. Mungale; Dr. Deepa A Joshi “Construction Techniques for Retrofitting by Jacketing of
RCC Member” international journal of innovations in engineering and technology (IJET) volume 6
issue 3 february 2016.
[2]. Kodur, V. R.; Sultan, M. A. “Effect of Temperature on Thermal Properties of HighStrength
Concrete”,Journal of Materials in Civil Engineering, 15, 2, pp. 101-107, (2003).
[3]. N. K. Raut, V. K. R. Kodur, F.ASCE, “Response of High-Strength Concrete Columns Under
Design Fire Exposure”,J. Struct. Eng. 2011.137:69-79, (2013).
[4]. S.H.Chowdhury, “Effect of Elevated Temperature on Mechanical Properties Of High Strength
Concrete”, 23rd Australasian Conference on the Mechanics of Structures and Materials (ACMSM23)
Byron Bay, Australia, 9-12 December 2014, S.T. Smith (Ed.),(2014).
[5]. VenkateshKodur, “Properties of Concrete at Elevated Temperatures”, Volume 2014, Article ID
468510.
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affected concrete structure 24

25. THANK YOU
Assessment method and Rehabilitation technique of fire
affected concrete structure
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