Performance of fire damaged cement and geopolymer concrete slabs retrofitted with BFRP laminates under static loading

Ulagambika, Patchirajan; Murugan, Madasamy

doi:10.1590/1517-7076-rmat-2024-0015

Patchirajan Ulagambika ^*Corresponding Author: Ulagambika Patchirajan

Anna University Chennai, Government College of Engineering, Department of Civil Engineering. 627007, Tirunelveli, Tamilnadu, India.

https://orcid.org/0009-0002-2841-4443

Madasamy Murugan

Anna University Chennai, Government College of Engineering, Department of Civil Engineering. 627007, Tirunelveli, Tamilnadu, India.

*

Corresponding Author: Ulagambika Patchirajan

e-mail: murugan@gcetly.ac.in, ambika5545@gmail.com

Figures (18)
Tables (7)

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Figure 1
Placing of reinforcement.

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Figure 2
Casting of specimens.

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Figure 3
Water curing of cement concrete slabs.

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Figure 4
Ambient curing of geopolymer concrete slabs.

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Figure 5
Set up for firing.

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Figure 6
Thermocouple.

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Figure 7
Exposure of fire on concrete slab.

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Figure 8
Fire damaged slabs.

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Figure 9
a) Surface cleaning process. b) Slab wrapped with BFRP laminates.

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Figure 10
Schematic representation of supporting condition of slab.

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Figure 11
a) Testing of fire damaged slab without wrapping. b) Testing of fire damaged slab retrofitted with BFRP laminates.

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Figure 12
Mass loss of cement concrete slabs subjected to different temperature and duration.

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Figure 13
Mass loss of geopolymer concrete slabs subjected to different temperature and duration.

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Figure 14
Overall comparison of Ultimate load carrying capacity of Cement and Geopolymer slabs at various temperatures and various durations.

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Figure 15
Failure mode of fire damaged cement concrete slab.

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Figure 16
Failure mode of fire damaged geopolymer concrete slab.

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Figure 17
Failure mode of fire damaged CC slabs wrapping with BFRP laminates.

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Figure 18
Failure mode of fire damaged GPC slabs wrapping with BFRP laminates.

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Table 1
Properties of cement.

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Table 2
Properties of geopolymer binder (FA80: GGBS20).

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Table 3
Properties of fine and coarse aggregate.

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Table 4
Properties of basalt FRP.

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Table 5
Ultimate load carrying capacity of cement and geopolymer concrete slabs subjected to different temperature and duration under static loading. Retrofit material: BFRP laminates.

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Table 6
Visual observation.

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Table 7
Physical and chemical response to fire.

S.NO	TESTS PERFORMED	EXPERIMENTED VALUES	REQUIREMENTS AS PER IS 12269-2013
1	Standard consistency	31%	28-32
2	Initial setting time	55 minutes	Not less than 30
3	Final setting time	285 minutes	Not more than 600
4	Specific gravity	3.11	3.15
5	Fineness (<90 microns)	2.5%	<10%
6	3^rd day compressive strength of cement	30.0 N/mm²	Greater than 27.0 N/mm²
7	7^th day compressive strength of cement	42.0 N/mm²	Greater than 37.0 N/mm²
8	28^th day compressive strength of cement	56.5 N/mm²	Greater than 53.0 N/mm²

S.NO	TESTS PERFORMED	EXPERIMENTED VALUES
1	Consistency test	30%
2	Initial setting time	76 minutes
3	Final setting time	285 minutes

S.NO	PROPERTY	FINE AGGREGATE	COARSE AGGREGATE
S.NO	PROPERTY	FINE AGGREGATE	20 mm	12.5 mm
1	Specific gravity	2.61	2.89	2.81
2	Fineness modulus	2.75	6.8	6
3	Density	1685 kg/m³	1760 kg/m³	1710 kg/m³
4	Water absorption	0.54%	0.211%	0.203%

PROPERTIES	WEIGHT OF FIBRE (G/M²)	FIBRE THICKNESS (MM)	NOMINAL THICKNESS PER LAYER (MM)	FIBRE TENSILE STRENGTH (N/MM²)	TENSILE MODULUS (N/MM²)
BFRP (Bidirectional)	330	0.60	1.0	4840	86000

EXPOSURE CONDITION		TYPE OF CONCRETE	LOAD CARRYING CAPACITY OF SLAB BEFORE RETROFIT (KN)	LOAD CARRYING CAPACITY OF SLAB (KN) AFTER RETROFIT	% OF INCREASE IN LOAD CARRYING
TEMPERATURE (ºC)	DURATION (HOUR)	TYPE OF CONCRETE	LOAD CARRYING CAPACITY OF SLAB BEFORE RETROFIT (KN)	LOAD CARRYING CAPACITY OF SLAB (KN) AFTER RETROFIT	% OF INCREASE IN LOAD CARRYING
Room temperature	–	Cement	34	61.20	80.00
Room temperature	–	Geopolymer	40	72.40	81.00
200	1	Cement	37.4	67.32	80.00
	1	Geopolymer	47.2	84.96	80.00
	2	Cement	33.32	59.64	78.99
	2	Geopolymer	43.2	77.33	79.00
	3	Cement	32.3	58.46	80.99
	3	Geopolymer	38.8	69.06	77.99
400	1	Cement	31.62`	56.92	80.01
	1	Geopolymer	39.2	70.56	80.00
	2	Cement	29.24	52.92	80.98
	2	Geopolymer	36.8	65.87	78.99
	3	Cement	27.2	48.42	78.01
	3	Geopolymer	34.4	61.23	77.99
600	1	Cement	28.9	52.02	80.00
	1	Geopolymer	36	64.44	79.00
	2	Cement	25.5	46.16	81.02
	2	Geopolymer	33.2	59.76	80.00
	3	Cement	22.1	39.34	78.01
	3	Geopolymer	30	53.70	79.00
800	1	Cement	22.78	40.78	79.02
	1	Geopolymer	28.8	51.84	80.00
	2	Cement	17.68	31.47	78.00
	2	Geopolymer	24.0	42.96	79.00
	3	Cement	13.6	24.21	78.01
	3	Geopolymer	20.4	36.72	80.00

TEMPERATURE (°C)	WHAT HAPPENS
200	The color transitions to light gray.
400	The color further changes to gray, and up to 400ºC, there are no visible thermal cracks on the surface of the exposed concrete.
600	As the temperature increases, the color shifts to light pink, and at this stage, minor cracks and surface crazing become visible.
800	The color transforms to Gainsboro gray, and at this point, higher surface cracking and crazing become observable.

TEMPERATURE (°C)	DURATION (HOUR)	WHAT HAPPENS
TEMPERATURE (°C)	DURATION (HOUR)	IN CEMENT CONCRETE SLABS	IN GEOPOLYMER CONCRETE SLABS
For 200	1	No cracks are observed	Geopolymer concrete exhibits no formation of cracks.
For 200	2	Very minor cracks formation was observed	No crack formation
For 200	3	Minor crack formation was identified.	There is no formation of cracks.
For 400	1	Some Minor cracks have formed.	Very minor cracks formation was noted.
For 400	2	Moderate cracks formation was observed	Minor cracks formation was observed.
For 400	3	Extensive cracks formation was noted.	Moderate Crack formation was noticed.
For 600	1	Cracks of medium size were observed.	Observations revealed the formation of minor cracks.
For 600	2	Extensive cracks were observed.	Moderate cracks formation without any spalling of the concrete.
For 600	3	Cracks of medium size appeared within the first hour, followed by substantial spalling starting 1at 2:30 hr. Beyond this temperature threshold, Concrete loses its full structural capacity	Large cracks have formed, and there is no occurrence of concrete spalling.
For 800 – 1 Hr	1	The surface of the concrete exhibited the formation of extensive cracks.	Moderate Crack formation was noticed.
For 800 – 2 Hrs	2	65% of very extensive cracks and spalling occur, accompanied by a distinct and heavy sound.	Substantial cracks, accompanied by slight spalling of the concrete, occur.
For 800 – 3Hrs	3	Nearly 90% of the concrete undergoes complete damage, characterized by extensive cracks and spalling, accompanied by a pronounced and heavy sound.	Extensive formation of large cracks is accompanied by concrete spalling.

[1] Corresponding Author: Ulagambika Patchirajan

Brasil

Brasil

Performance of fire damaged cement and geopolymer concrete slabs retrofitted with BFRP laminates under static loading

ABSTRACT