The document discusses a study on the elevated temperature properties of fiber reinforced phosphogypsum concrete. Phosphogypsum, a byproduct of phosphoric acid production, was used to partially replace cement at levels of 0%, 10%, 20%, and 30%. Concrete cubes and cylinders containing 0.75% steel fibers were cured and then exposed to temperatures of 100°C, 200°C, and 300°C for varying durations. Compressive strength was found to decrease with increasing temperature and phosphogypsum content, with up to a 42% reduction observed.

1. http://www.iaeme.com/IJCIET/index.asp 234 editor@iaeme.com
International Journal of Civil Engineering and Technology (IJCIET)
Volume 7, Issue 2, March-April 2016, pp. 234–246, Article ID: IJCIET_07_02_021
Available online at
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=7&IType=2
Journal Impact Factor (2016): 9.7820 (Calculated by GISI) www.jifactor.com
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication
STUDIES ON ELEVATED TEMPERATURE
OF FIBER REINFORCED
PHOSPHOGYPSUM CONCRETE
Umadevi R
Research Scholar, Department of Civil Engineering,
BMS College of Engineering, INDIA
Kavitha S
Research Scholar, Department of Civil Engineering,
Dr MGR Educational Research Institute & University, INDIA
Shashi kiran C R
Research Scholar, Department of Civil Engineering,
BMS College of Engineering, INDIA
Sugandha N
Asst Professor, Department of Civil Engineering,
ACS College of Engineering, INDIA
ABSTRACT
Deterioration of concrete structures due to steel corrosion is a matter of
considerable concern since the repairing of these structures proved to be a
costly process. Repair and rehabilitation of the civil structures needs an
enduring repair material. The ideal durable material should have low
shrinkage, good thermal expansion, and substantial modulus of elasticity, high
tensile strength, improved fatigue and impact resistance. Fire represents one
of the most severe exposure conditions and hence provisions for appropriate
fire resistance for structural members are major safety requirements for any
building design.
The present paper deals with the experimental investigation on elevated
temperature of concrete and compressive, tensile strength of partially cement
replaced phosphogypsum concrete and 0.75% of fiber reinforced and 0%,
10%, 20% & 30% replacement with water-binder ration of 0.50 are studied. It
is shown that a part of Ordinary Portland cement can be replaced with
phosphogypsum to develop a good and hardened concrete economically.
Key words: Phosphogypsum (PG), Flexural Strength, Fiber Reinforced
concrete (FRC)

2. Studies on Elevated Temperature of Fiber Reinforced Phosphogypsum Concrete
http://www.iaeme.com/IJCIET/index.asp 235 editor@iaeme.com
Cite this Article: Umadevi R, Kavitha S, Shashi kiran C R and Sugandha N,
Studies on Elevated Temperature of Fiber Reinforced Phosphogypsum
Concrete, International Journal of Civil Engineering and Technology, 7(2),
2016, pp. 226–233.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=7&IType=2
1. INTRODUCTION
Fiber Reinforced concrete (FRC) may be defined as a composite materials made with
Portland cement, aggregate and incorporating discrete discontinuous fibres. Plain
concrete possesses a very low tensile strength, limited ductility and Plain concrete
possesses a very low tensile strength, limited ductility and little resistance to cracking.
Internal micro cracks are inherently present in the concrete and its poor tensile
strength is due to the propagation of such micro cracks, eventually leading to brittle
fracture of the concrete. It has been recognized that the addition of small, closely
spaced and uniformly dispersed fibers to the concrete would act as crack arrester and
would substantially improve its Compressive and flexural strength properties. This
type of concrete is known as “fiber reinforced concrete”.
Civil structures made of steel reinforced concrete normally suffer from corrosion
normally suffer corrosion of the steel by the salt, which results in the failure of those
structures. Constant maintenance and repairing is needed to enhance the life cycle of
those civil structures. There are many ways to minimize the failure of the concrete
structures made of steel reinforce concrete. The custom approach is to adhesively
bond fibers polymer composites onto the structure. This also helps to increase the
toughness and tensile strength and improve the racking and deformation
characteristics of the resultant composite. But this method adds another layer, which
is prone to degradation. These fibers polymer composites have been shown to suffer
from degradation when exposed to marine environment due to surface blistering. As
a results, the adhesive bond strength is reduced, which results in the de-lamination of
the composite. Another approach is to replace the bars in the steel with fibers to
produce a fiber reinforced concrete and this is termed as FRC. Basically this method
of reinforcing the concrete substantially alters the properties of the non-reinforced
cement-based matrix which is brittle in nature. Possessed little tensile strength
compared to the inherent compressive strength.
The principal reason for incorporating fiber into a cement matrix is to increase the
toughness and tensile strength, and improve the cracking deformation characteristics
of the resultant composite. In order for fibers reinforced concrete (FRC) to be a
viable construction material, it must be able to compete economically with existing
reinforcing systems.
2. MATERIALS AND METHODOLOGY
Experimental investigation was planned to provide sufficient information about the
resistance of fiber reinforced Phosphogypsum based cement concrete.
MATERIALS USED
The different materials used in this investigation are:
 53 grade ordinary Portland cement
 Coarse Aggregate
 Fine Aggregate

3. Umadevi R, Kavitha S, Shashi kiran C R and Sugandha N
http://www.iaeme.com/IJCIET/index.asp 236 editor@iaeme.com
 Phospogypsum
 Steel Fiber
Cement
The cement used in all mixtures was commercially available 53 grade Ordinary
Portland Cement (OPC).
Coarse aggregates
The coarse aggregate having 20mm normal size well-graded aggregate according to
IS-383 is used in this study. The coarse aggregate procured from quarry was sieved
through 20mm, 16mm, 12.5mm, 10mm and 4.75mm sieves. The material retained on
12.5mm, 10mm and 4.75mm sieves was filled in bags and stacked separately and used
in the production of Self Compacting Concrete.
Fine aggregates
The fine aggregate that falls in zone-I was obtained from a nearby river course. The
sand obtained was sieved through all the sieves (i.e.4.75mm, 2.36mm, 1.18mm, 600,
300, 150). Sand retained on each sieve was filled in different bags and stacked
separately for use. To obtain zone-I sand correctly, sand retained on each sieve is
mixed in appropriate proportion.
Phosphogypsum
Generally, a ton of phosphoric acid production generates about 4.5 to 5 tonnes of
phospho-gypsum. Major phosphogypsum producing fertilizer units are Coromandal
Fertilizer Ltd, Visakhapatnam in Andhra Pradesh; Gujarat State Fertilizers and
Chemicals Ltd, Vadodara in Gujarat; FACT Udyogmandal, Ernakulam in Kerala,
RCF, Chembur, Mumbai in Maharashtra; Paradeep Phosphates Ltd in Orissa, SPIC
Tuticorin and Coromandal Fertilizers Ltd, Thiruvalur in Tamil Nadu.
Phosphogypsum is a by-product in the wet process for manufacture of phosphoric
acid (ammonium phosphate fertilizer) by the action of sulphuric acid on the rock
phosphate. It is produced by various processes such as dehydrate, hemihydrate or
anhydrite processes. In India the majority of phosphogypsum is produced by the
dehydrate process due to its simplicity in operation and lower maintenance as
compared to other processes. The other sources of phosphogypsum are by-products of
hydrofluoric acid and boric acid industries.
Figure 1 Phosphogypsum Material

4. Studies on Elevated Temperature of Fiber Reinforced Phosphogypsum Concrete
http://www.iaeme.com/IJCIET/index.asp 237 editor@iaeme.com
Current worldwide production of phosphoric acid yields over 100 million tons of
phosphogypsum per year. While most of the rest of the world looked at
phosphogypsum as a valuable raw material and developed process to utilize it in
chemical manufacture and building products, India blessed with abundant low-cost
natural gypsum piled the phosphogypsum up rather than bear the additional expense
of utilizing it as a raw material. It should be noted that during most of this time period
the primary reason phosphogypsum was not used for construction products in India
was because it contained small quantities of silica, fluorine and phosphate (P205) as
impurities and fuel was required to dry it before it could be processed for some
applications as a substitute for natural gypsum, which is a material of higher purity.
However, these impurities impair the strength development of calcined products. It
has only been in recent years that the question of radioactivity has been raised and this
question now influences every decision relative to potential use in building products
in this country.
Some attempts have been made to utilize phosphogypsum as base and fill
materials (in the form of cement-stabilized phosphogypsum mix) in the construction
of highways, runways, etc. In other attempts, phosphogypsum was recycled for
manufacture of fibrous gypsum boards, blocks, gypsum plaster, composite mortars
using Portland cement, masonry cement, and super-sulphate cement.
Steel Fibers
Fibers reinforced concrete may be defined as composite materials made with Portland
cement, aggregate and incorporating discrete discontinuous fibers.
When the fiber reinforcement is in the form of short discrete fibers, they act
effectively as rigid inclusions in the concrete matrix. Physically, they have thus the
same order of magnitude as aggregate inclusions, steel fibers reinforcement cannot be
therefore regarded as a direct replacement of longitudinal reinforcement in reinforced
and prestressed structural members. However, because of the inherent material
properties of fibers concrete, the presence of fibers in the body of the concrete or the
provision of a tensile skin of fibers concrete can be expected to improve the resistance
of conventionally reinforced structural members to cracking, deflection and other
serviceability conditions.
Figure 2 Shape of Steel fibers

5. Umadevi R, Kavitha S, Shashi kiran C R and Sugandha N
http://www.iaeme.com/IJCIET/index.asp 238 editor@iaeme.com
The fibers reinforcmement may be used in the form of three – dimensionally
randomly distributed fibers throughout the structual member when the added
advantages of the fibers to shear resistance and crack control can be further utilised.
One the other hand, the fiber reinforced concrete may also be used as a tensile skin to
cover the steel reinforcment when a more efficeint two – dimensional orientation of
the fibers could be obtained.
Technical Data and specification of steel fibre:
Type of steel fiber reinforced : Crimped steel fiber
Size : 0.50mm dia & 30mm length
Strength of strain resistance : More than 1100 N/mm2
Repeated flexure : 3 times
Density : 7.83mm3
Average in cross section : 1.716 mm2
Figure 3 Crimped Steel Fiber Reinforced material
Water
The potable water, which is free from concentration of acids and organic substances
was used for mixing the concrete.
METHODOLOGY
An experimental study is conducted on fiber reinforced cement concrete by
replacing 10%, 20%, 30% of cement by Phosphogypsum and total volume of concrete
by 0.75% of fiber reinforcement for different elevated temperatures. Absolute volume
method is carried out with various percentages of Phosphogypsum replacing cement
has been made use in the present investigation. The test consisted of carrying out
compressive strength test on cubes, split tensile strength test on cylinders and to study
the strength variation of concrete with addition of fiber reinforcement and
phosphogypsum partially.

6. Studies on Elevated Temperature of Fiber Reinforced Phosphogypsum Concrete
http://www.iaeme.com/IJCIET/index.asp 239 editor@iaeme.com
Design Mix Proportion Used in Phosphogypsum & Steel Fiber Reinforced
Concrete for M20 Grade
Water Cement Fine aggregate Coarse aggregate
191.6 litre 383 kg 600 kg 1144 kg
0.50 : 1 : 1.567 : 2.987
Experimental investigations were carried out to study the physical properties of all
the materials used and the results are tabulated
Table1 Physical properties of cement
Sl. No Property Experimental Values
Suggested value as per IS:
12269-1987 code
1. Specific gravity 3.15 3.14
2. Normal Consistency 33.75% -
3. Initial Setting Time 75min Min 30 minutes
4. Final Setting Time 245min Max 10 Hours
Table 2 Physical properties of aggregate
Sl. No Property coarse aggregate fine aggregate
1. Specific gravity 2.67 2.61
2. Bulk density 1239 Kg/m3
1574 Kg/m3
3. Water Absorption 0.5%
4. Fineness modulus 7.36 3.14
5 Grading Zone-I
Table 3 Abstract of workability values of fresh of Steel fiber reinforced & phosphogypsum
concrete mixes
Sl. No % of Phosphogypsum
% of
Steel
fiber
Slump
value
Compaction
factor value
Vee - Bee
degree
(seconds)
1 0% 0.75 24.6 0.85 4.8
2 10% 0.75 26.0 0.84 7.3
3 20% 0.75 27.4 0.82 9.0
4 30% 0.75 29.1 0.74 12.5
3. ANALYSIS AND DISCUSSIONS
Experiments were carried out to study the Strength of Steel fiber reinforced
phosphogypsum concrete. Cubes and cylinders were casted by replacing cement with
phosphogypsum for 10%, 20%, 30% and cured for 28days. The cubes and cylinders
were exposed to elevated temperature for different durations. The results obtained
were tabulated

7. Umadevi R, Kavitha S, Shashi kiran C R and Sugandha N
http://www.iaeme.com/IJCIET/index.asp 240 editor@iaeme.com
Table 4 Compressive Strength of Steel fiber & Phosphogypsum Mixes at Elevated
Temperatures
Sl.N
o.
Designation
of Mix
Temperatur
e in 0
C
Duration of
Exposure in
hrs
Compressive
strength (Mpa)
% Variation over
reference mix
% Varitation of
corresponding mix at
room temperature
Increase Decrease Increase Decrease
1 0% of PG RoomTemp 31.52
100 4 32.11 1.87
6 32.98 4.63
8 30.02 4.76
200 4 29.47 6.50
6 27.88 11.55
8 25.55 18.94
300 4 24.53 22.18
6 22.64 28.17
8 19.82 37.12
2 10% of PG Room Temp 34.21 8.53
100 4 34.60 7.74 1.13
6 35.09 6.40 2.57
8 33.87 12.82 1.00
200 4 33.62 14.07 1.74
6 32.47 16.47 5.08
8 31.69 24.04 7.36
300 4 30.54 24.48 10.74
6 29.28 29.34 14.41
8 28.34 42.97 17.17
3 20% of PG Room Temp 21.78 30.90
100 4 22.47 30.01 3.18
6 23.31 29.32 7.02
8 21.74 27.59 0.20
200 4 21.67 26.47 0.51
6 20.91 25.00 3.99
8 20.57 19.49 5.56
300 4 20.01 18.43 8.13
6 19.67 13.13 9.70
8 18.58 6.26 14.70
4 30% of PG Room Temp 16.61 47.30
100 4 16.87 47.45 1.59
6 17.14 48.04 3.18
8 16.41 45.33 1.19
200 4 15.95 45.88 3.97
6 15.41 44.72 7.22
8 15.10 40.89 9.07
300 4 14.67 40.18 11.66
6 14.11 37.66 15.03
8 13.61 31.35 18.08

8. Studies on Elevated Temperature of Fiber Reinforced Phosphogypsum Concrete
http://www.iaeme.com/IJCIET/index.asp 241 editor@iaeme.com
Table 5 Split tensile Strengths of Steel Fiber & Phosphogypsum Mixes at Elevated
Temperatures
Sl.No
Designation
of Mix
Temperat
ure in 0
C
Duration
of
Exposure
in hrs
Split tensile
Streng th
(Mpa)
% Variation over
reference mix
% Varitation of
corresponding mix
at room
temperature
Increase Decrease Increase Decrease
1. 0% of PG
Room
Temp
3.83
100 4 4.13 7.83
6 4.54 18.54
8 3.07 19.84
200 4 2.94 23.24
6 2.85 25.59
8 2.56 33.16
300 4 2.32 39.43
6 2.10 45.17
8 1.63 57.44
2 10% of PG
Room
Temp
5.21 36.07
100 4 5.69 37.78 9.20
6 5.95 31.15 14.25
8 3.82 24.48 26.67
200 4 3.75 27.54 28.05
6 3.71 30.31 28.74
8 3.64 42.26 30.11
300 4 3.35 44.59 35.63
6 3.27 55.74 37.24
8 3.08 88.89 40.92
3 20% of PG
Room
Temp
3.08 19.61
100 4 3.31 19.94 7.39
6 3.56 21.63 15.56
8 2.76 10.25 10.51
200 4 2.70 8.32 12.45
6 2.66 6.68 13.62
8 2.37 7.34 22.96
300 4 2.22 4.47 28.02
6 2.01 4.16 34.63
8 1.57 3.72 49.03
4 30% of PG
Room
Temp
2.37 38.07
100 4 2.55 38.21 7.58
6 2.66 41.42 12.12
8 2.34 23.91 1.52
200 4 2.29 22.17 3.54
6 2.18 23.50 8.08
8 2.04 20.45 14.14
300 4 1.94 16.35 18.18
6 1.83 12.72 22.73
8 1.46 10.33 38.38

9. Umadevi R, Kavitha S, Shashi kiran C R and Sugandha N
http://www.iaeme.com/IJCIET/index.asp 242 editor@iaeme.com
Figure 4 Variation of compressive strength for change in % replacement of cement by
phosphogypsum at room temp
Figure 5 Variation of split tensile strength for change in % replacement of cement by
phosphogypsum at room temp
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
0% 10% 20% 30%
PG+FR (Room Temp.)
% REPLACEMENT OF CEMENT BY PHOSPHOGYPSUM
CompressiveSTRENGTH(Mpa)
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0% 10% 20% 30%
PG+FR (Room Temp.)
% REPLACEMENT OF CEMENT BY PHOSPHOGYPSUM
SPLITTENSILESTRENGTH(Mpa)

10. Studies on Elevated Temperature of Fiber Reinforced Phosphogypsum Concrete
http://www.iaeme.com/IJCIET/index.asp 243 editor@iaeme.com
Figure 6 Variation of compressive strength for change in % replacement of cement by
phosphogypsum at 1000
C
Figure 7 Variation of compressive strength for change in % replacement of cement by
phosphogypsum at 2000
C
0
5
10
15
20
25
30
35
40
0% 10% 20% 30%
4 Hrs
6 Hrs
8 Hrs
COMPRESSIVESTRENGTH(Mpa)
PG+FR(1000C)
% REPLACEMENT OF CEMENT BY PHOSPHOGYPSUM
0
5
10
15
20
25
30
35
40
0% 10% 20% 30%
4 Hrs
6 Hrs
8 Hrs
COMPRESSIVESTRENGTH(Mpa)
PG+FR(2000C)
% REPLACEMENT OF CEMENT BY PHOSPHOGYPSUM

11. Umadevi R, Kavitha S, Shashi kiran C R and Sugandha N
http://www.iaeme.com/IJCIET/index.asp 244 editor@iaeme.com
Figure 8 Variation of compressive strength for change in % replacement of cement by
phosphogypsum at 3000
C
Figure 9 Variation of Split tensile strength for change in % replacement of cement by
phosphogypsum at 1000
C
0
5
10
15
20
25
30
35
0% 10% 20% 30%
4 Hrs
6 Hrs
8 Hrs
COMPRESSIVE
STRENGTH(Mpa)
PG+FR(3000C)
% REPLACEMENT OF CEMENT BY PHOSPHOGYPSUM
0
1
2
3
4
5
6
7
0% 10% 20% 30%
4 Hrs
6 Hrs
8 Hrs
SPLITTENSILESTRENGTH(Mpa)
PG+FR(1000C)
% REPLACEMENT OF CEMENT BY PHOSPHOGYPSUM

12. Studies on Elevated Temperature of Fiber Reinforced Phosphogypsum Concrete
http://www.iaeme.com/IJCIET/index.asp 245 editor@iaeme.com
Figure 9 Variation of split tensile strength for change in % replacement of cement by
phosphogypsum at 2000
C
Figure 10 Variation of split tensile strength for change in % replacement of cement by
phosphogypsum at 3000
C
From Fig 4 to Fig 10 it is observed that both compressive strength and split tensile
strength increased at 10 % replacement of cement by phosphogypsum even at
different elevated temperatures and duration of exposure.
It is also observed that there is decrease in compressive strength and split tensile
strength for replacing cement by phospogypsum greater than 10%, however up to
20% replacement of cement by phosphogypsum has same strength as that of
conventional concrete.
0
0.5
1
1.5
2
2.5
3
3.5
4
0% 10% 20% 30%
4 Hrs
6 Hrs
8 Hrs
SPLITTENSILESTRENGTH(Mpa)
PG+FR(2000C)
% REPLACEMENT OF CEMENT BY PHOSPHOGYPSUM
0
0.5
1
1.5
2
2.5
3
3.5
4
0% 10% 20% 30%
4 Hrs
6 Hrs
8 Hrs
SPLITTENSILESTRENGTH(Mpa)
PG+FR(3000C)
% REPLACEMENT OF CEMENT BY PHOSPHOGYPSUM

13. Umadevi R, Kavitha S, Shashi kiran C R and Sugandha N
http://www.iaeme.com/IJCIET/index.asp 246 editor@iaeme.com
4. CONCLUSIONS
Based on experimental investigation conducted and the analysis of test results, the
following has been concluded.
 From the study it is observed that up to 10% phosphogypsum & steel fiber
reinforcement is the optimum dosage which can be mixed as partial replacement to
cement for giving maximum possible increase of compressive strength and split
tensile strength.
 It was also observed that for 10% phosphogypsum both the compressive strength and
split tensile strength was is high at 1000
C for exposure duration of 4 and 6 hrs.
 The normal transporting, placing and finishing methods used for plain concrete can
also used for SFRPGC.
REFERENCES
[1] M. Singh, Physio – chemical studies on phosphogypsum for use in building
materials, Ph. D.thesis, University of Roorkee, Roorkee, India, 1980.
[2] N. Ghafoori, Phosphogypsum based concrete: Engineering characteristics and
road applications,Ph. D. thesis, University of Miami, Corel Gables, Florida,
(December 1986).
[3] W. F. Chang, and M. I. Mantell., Engineering properties and construction
applications of phosphogypsum, University of Miami press, Florida, 1990.
[4] R. K. H. Ho, R. W. Williams, L. L. Cogdill and W. F. Chang., Columbia county
experimental road,Volume II, Proceedings of the second International symposium
on phosphogypsum, University of Miami, Florida Institute of Phosphate
Research, Bartow, Florida, (January 1988) 397 – 416.
[5] M. M. Smadi, R. H. Haddad and A. M. Akour., Potential use of phosphogypsum
in concrete,Cement and Concrete Research, Volume 29, Number 7, (1999) 1419
– 1425.
[6] IS: 12679 - 1989. “By-product gypsum for the use in plaster, blocks and boards
specification.”Bureau of Indian Standards, New Delhi.