20320140504002

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME
10
EFFECT OF ELEVATED TEMPERATURE ON SOME PROPERTIES OF
TECHNICAL GYPSUM REINFORCED BY CELLULOSE FIBER
Abbas S. Al-Ameeri1
1
(Civil, Engineering/ University of Babylon, Babylon City, Iraq)
ABSTRACT
In spite of the wide availability of gypsum called juss in Iraq, with a low cost, but it still used
mainly as a finishing material in plastering.
The present work aim is to study the effect of elevated temperate exposure on properties of
cellulose fiber reinforced gypsum (FCG), namely (density, compressive strength, flexural strength
and ultrasonic pulse velocity). Technical gypsum was exposed to elevated temperature (25, 200, 400
and 600°C) with two different exposure durations of (0.5 and 1 hours). Specimens were exposed to
temperature and tested at age 28 days. The results indicate that Elevated temperatures and increasing
of exposure duration had passively influenced on hardened properties of both plain and fiber
reinforced gypsum. The hardened properties of two type of technical gypsum decreased with
increased temperatures and increasing of exposure duration. Deterioration in strength increases with
increases in periods of exposure to elevated temperatures for all mixes. The residual density of
technical gypsum ranged between (93-88%) at 200 o
C, (85-79%) at 400 o
C and (82-80%) at 600 o
C
for all mixes. The residual compressive strength ranged between (52-98%) at 200 o
C, (19-36%) at
400 o
C and (13-26%) at 600 o
C for mixes. The flexural strength was very sensitive to temperatures.
Residual flexural strengths ranged between (41-84%) at 200 o
C, and became zero at 400o
C and 600
o
C for all mixes. The residual ultrasonic pulse velocity was ranged between (68-83%) at 200 o
C,
(45-63%) at 400 o
C and (43-50%) at 600 o
C for mixes. Also the results indicate that cellulose fiber
used in gypsum reduced the amount of deterioration of properties of fiber-reinforced gypsum (FCG)
at 40 ᵒC and 200 ᵒC temperature, and the cellulosic fiber helped to improve the flexural strength of
gypsum samples at 40 ᵒC and 200 ᵒC, and improvement the compressive strength gypsum samples at
200 ᵒC.
Keywords: Elevated Temperature, Cellulose Fiber, Cellulose Fiber Reinforced Gypsum, Gypsum,
Technical Gypsum.
INTERNATIONAL JOURNAL OF CIVIL ENGINEERING
AND TECHNOLOGY (IJCIET)
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 5, Issue 4, April (2014), pp. 10-27
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11
1- INTRODUCTION
Historians agree that the Iraqis are first to discover the bricks and plaster used in construction
in Babylon and Nineveh. Building gypsum(Stucco) is a calcium sulphate united with a half molecule
of water CaSO4.1/2 H2O) With strange substances in different percentage like (CaCo3 SiO2 , Al2O3).
It is made from burning of gypsum deposits which is (CaSO4 . 2 H2O) a hydrous calcium sulphate).
Pure gypsum is a white translucent crystalline mineral and is so soft that it can be scratched by a
finger nail. When heated to 205°C, pure gypsum loses its luster and its specific gravity is increased
from 2.3 to 2.95 due to the loss of water of crystallization [1].
In Iraq, there are two commercial varieties of crude gypsum, rock gypsum and gypsum or
gypsite, Gypsum stone can be considered as sedimentary rocks, and can be classified metallically as
a hydrous calcium sulphate (CaSO4. 2H2O) and some percentage of defect such as
(2SiO2.Al2O3.2H2O), can be found in different forms locally called (Alabaster, Selenite, Gypsite,
Massive gypsum rocks and Santinspar)[2].
The water of crystallization in the gypsum (CaSO4. 2H2O) is not held firmly by the mineral.
Therefore, when it is heated to about (130-175)°C, it loses a part of water of crystallization and is
known as half-hydrate gypsum or (hemihydrate calcined gypsum) according Eq. (1-1)[3] [1].
At still higher temperatures (About 200°C), gypsum loses all its water of crystallization and
turns out into an hydrate soluble gypsum. When we increase the heat the gypsum turns out into (an
hydrated un soluble gypsum) according Eq. (1-2).
At high temperature of (1000 -1200) ºC the compound that results is called ( lime ), according
Eq. (1-3).
The lost water of crystallization can be regained under favorable damp or moist conditions
according Eq. (1-4) and (1-5).
CaSO4.2H2O CaSO4.1/2H2O
130- 175
ᵒ
C
+ 3/2H2O
(hemihydrate calcined gypsum)
Eq. (1-1).......
CaSO4.1/2H2O CaSO4
205- 400
ᵒ
C
+ 1/2H2O
(an hydrated soluble gypsum)
Eq (1-2).......
CaSO4 CaO
1000-1200 ᵒ
C
+ SO3
(Lime )
Eq (1-3).......
Eq (1-4).......CaSO4.2H2OCaSO4.1/2H2O
Hydration
+ 3/2H2O

12
When a half hydrated gypsum(Stucco) is mixed with water ,the reaction occurs universally as
in the equations (1-4)(1-5). According to the crystallization theory proposed by Le-chatelier when
water is added to gypsum, the latter dissolves forming a saturated solution of dehydrate gypsum.
Since the solubility of semihydrate gypsum is about 3.5 times more than of dehydrated gypsum[1].
This will form acicular crystals which grow during their formation and inter look with each another
and cohere. The size, shape and the velocity of crystals formation and its cohesion depends on type
of raw material, method of preparation and the strange substances found in the raw materials [3].
Building Gypsum(Stucco) can be classified according to British Standard ( BS 1911)[4] into
four types, Class A: include calcium sulphate united with a half molecule of water (CaSO4.1/2 H2O)
with high purity which called (Plaster of Paris), Class B: similar to class A with some retarders used
in different finishing, but Class C and Class D (keen, s cement) are an hydrated calcium sulphate
(CaSO4) which characterized by slow setting time so accelerators may be used to improve setting
time. The four types used in finishing purposes and precast units, gypsum boards, partitions and
sound isolations in various buildings but not as binder material for building of unites. Sometime is
used artificial or animal hair could be added to gypsum to reduce cracking.
Gypsum products(Stucco) can be classified according to Iraqi standard (IQS 28- 1988) [5]
into, Ordinary gypsum, Technical gypsum and Plaster of Paris, all types of gypsum are half-hydrate
gypsum or (hemihydrate calcined gypsum), but they have different physical and chemical properties
due to present on strange substances. The major application of gypsum is as a binder, finishing
materials, precast units, gypsum boards, partitions and sound isolations in various buildings.
According to the available literature, few investigations were carried out on gypsum material.
Several recent and past studies were conducted on using some types of additives to improve and
control the setting time, hydration, strength development, water resisting property and volume
change characteristics of gypsum [6] [7] [8] [9] [10].
Another presented the effect of addition some chemical admixtures to gypsum was also
studied to product suitable composition matrix for application on external brick walls exposed to
weathering conditions [11] to improve the good performance in tensile strength of gypsum
application were found by added the fiber to gypsum such as blocks or plates. The Various kinds of
fiber are used to reinforce gypsum in structural applications, such as animal hair, artificial fiber and
cellulose fiber from plant origin, all fiber must not affected by the corrosion phenomenon by building
gypsum (stucco).
In gypsum, the fibers have been applied to decrease width of cracks, to increase tensile and
flexural strength, and to improve post-cracking behavior. fiber reinforcement influences the way
cracks develop in gypsum and may impart improved crack growth resistance, increase surface
roughness of individual cracks, and a greater likelihood for crack branching and multiple crack
development, due to this[12].
AL-Baghdadi[13] found the best results of improvement the mechanical properties for stucco
mortar reinforced by reed and coconuts skin fibers, with increasing of addition ratio together with
fiber length up to (3%) and length of 40 mm for reeds and up to 4% with fiber length of 30mm for
coconuts skin fibers, the amount of increasing in compressive strength ,tensile strength and modulus
of rupture were (21,20,12)% respectively for reeds and (21,27,8)% respectively for coconuts fibers
with respect to reference sample .
AL-Naiemi [14] found the used cellulose fibers of palm trees increase the ductility, resilience
and toughness, and the fiber also increased the ultimate tensile strength and decreased in
compressive strength with reference samples.
CaSO4.2H2OCaSO4
Hydration
+ 2H2O
Eq (1-5).......

13
In the structural design of buildings, in addition to the normal gravity and lateral loads, it is,
in many cases, necessary to design the buildings to safely resist exposure to fire [15]. It is also
necessary to protect the building members such as beams, columns, slabs and walls by plastering
materials (cement mortar and gypsum mortar) as finishing to decrease the structural deterioration for
certain period of fire exposure. Such deterioration can be decreased if good finishing materials were
used in the building. There are many ways of exposing buildings to fire. One of the most common
types of exposure is by accidental fire. Normally such fires are of short duration but at high intensity
with the temperature reached up to 1000 o
C. Another type of heat exposure may be found in places
exposed to sustained elevated temperatures ranging from 100-1000 o
C. .
Muhammed [16] found the compressive strength of the specimens at temperature up to 100
o
C exhibited a slight increase as compared with reference values. And all gypsum specimens suffered
a significant decreases in compressive strength when exposed to 500 o
C and above. After a period of
0.50 hour, the exposure period was seen to have a slight effect on the residual strength of ordinary
gypsum except at 900 o
C. The results also show that no residual strength was observed at 500 and
900 o
C for the plaster of Paris and ordinary gypsum specimens respectively. .
In this study there is an attempt to investigate the influence of elevated temperature and
exposure periods on the properties of technical gypsum reinforced by cellulose fiber. However, still
limited amount of published literature is available about gypsum material.
2- EXPERIMENTAL PROGRAM
2-1 Material
2-1-1 Technical gypsum (Stucco)
Technical gypsum (Stucco) was used in this study. (Stucco) was produced by Faloja Factory
for Gypsum productions. The chemical analysis carried out according Iraqi Specification
(I.Q.S.No.273 -91)[17], and physical properties were tested by using (I.Q.S. No.27 -88)[18] as
shown in Table (2-1), physical and chemical properties were conformed to the Iraqi specifications
(I.Q.S. No.28 -88)[5] requirements.
Table (2-1): Physical and Chemical properties of Technical gypsum
Physical properties
properties
Test
results
Limits of Iraqi specification
No.28/1988
Fineness(remaining on sieve No.16 (1.18mm)) (%) 4 5
Initial setting time (Min.) 15 12 - 20
Compressive strength (N/mm2) 6 ≥ 6
Modulus of Rupture (N/mm2) 3 ≥ 2
Hardness Strength ( indention diameter of drop ball
(dia.12.7 mm )) ( mm )
3 ≤ 5
Chemical properties
Oxide composition
Test results
(%)
Limits of Iraqi specification
No.28/1988
Sulphur trioxide (SO3) 52 40≥
Calcium oxide (CaO) 35 27≥
Soluble residual 0.2 0.25≤
Combined Water 6 9≤
Loss on Ignition (L.O.I) 4 9≤
Defects 2.8 ---

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976
ISSN 0976 – 6316(Online), Volume 5, Issue 4, April (2014), pp.
2-1-2 Water
The potable water has been used for mixing with gypsum in this work.
2-1-3 Fibers
In this work, type of cellulose fiber
used. The characteristics of the cellulose
were 25mm, (0.1-0.5) mm, 250 MPa and 0.9
2.2. Methodology
The mix design method used in the present study was according to Iraqi Specification (IQS
27-88) [18]. The (water/ gypsum) used in the study was (0.64) by weight. Fibers were added in
quantities ranging from 0 to 6 % by volume of the total mixture. Fibers were fed into mixed by hand
to ensure that clumping and clustering effects were minimized. Fiber
in Table (2).
Table (2-
Mix No. Mix Symbol
1 R
2 FC1
3 FC2
4 FC3
The mixes being cast into the moulds until it's fully filled. All specimens were demoulded
after final setting, and kept out at laboratory weather until the test
The specimens are exposed to different temperatures in an electrical furnace, the specimens
were tested at the ages of (28 days).
with two different exposure duration of 0.5 and 1 hour. After h
cool inside the electrical furnace for 2 hours after end of the heating and stored in a laboratory
environment about 24 hours , the test were carried out for specimens.
Plate (2-1): Cellulose fibers used in the study
6316(Online), Volume 5, Issue 4, April (2014), pp. 10-27 © IAEME
14
The potable water has been used for mixing with gypsum in this work.
In this work, type of cellulose fiber from plant origin having geometry of cylindrical was
cellulose fiber; length, diameter, tensile strength, specific gravity
250 MPa and 0.9 kg/cm3 respectively, as shown in Plate (2
[18]. The (water/ gypsum) used in the study was (0.64) by weight. Fibers were added in
to ensure that clumping and clustering effects were minimized. Fiber content in mixtures are detailed
-2): Fiber content in SCFRC mixtures
Mix Symbol Fiber Content (Vol.%)
R Reference mix without fiber
FC1 2 % cellulose fiber
FC2 4 % cellulose fiber
FC3 6% cellulose fiber
after final setting, and kept out at laboratory weather until the test as shown in Plate (2
were tested at the ages of (28 days). Four temperature levels of 40, 200, 400 and 600
with two different exposure duration of 0.5 and 1 hour. After heating, the specimens were allowed to
environment about 24 hours , the test were carried out for specimens.
Cellulose fibers used in the study Plate (2-2): Sample were stored at laboratory
having geometry of cylindrical was
tensile strength, specific gravity
kg/cm3 respectively, as shown in Plate (2-1).
[18]. The (water/ gypsum) used in the study was (0.64) by weight. Fibers were added in
content in mixtures are detailed
as shown in Plate (2-2).
200, 400 and 600 o
C were chosen
eating, the specimens were allowed to
Sample were stored at laboratory

15
2.3 Testing program
The mechanical properties studied were compressive strength, flexural strength and
ultrasonic pulse velocity. Furthermore, Density test was used. The compressive strength test was
performed in accordance with IQS No.27-1988 using 50 mm cube specimens. The density test was
carried out on 50 mm cube specimens. The test procedure given in IQS No.27-1988 was used to
determine the flexural strength using 40 × 40 × 160 mm prisms. The ultrasonic pulse velocity was
performed according to IQS No.300-1993[19] by using 40 × 40 × 160 mm prisms.
3. RESULTS AND DISCUSSIONS
3.1. The fresh Properties of Gypsum
All mixes of technical gypsum (TG) and Cellulose Fiber Reinforced gypsum (FCG). The
workability were decreased with increasing of Cellulose Fiber content. These test was carried out by
slump flow by using hollow pipe with dimension (dia 3.5 cm and height 5cm), this test was tested
according IQS (27-1988). The setting time of gypsum were decreased with increasing of Cellulose
Fiber content.
3.2. The effect of Cellulose fiber on hardened properties of technical gypsum exposure to
elevated temperatures
3.2.1 Density of Technical gypsum samples
Results are reported in Table(3-1). It was observed that bulk density decreases with
increasing temperatures. Figs.(3-1) through (3-4) show the relation between bulk density and
elevated temperature for all specimens at age (28) days. While Table (3-1) and Figs.(3-2) show the
percentage residual bulk density values which are found for the mixes of Technical gypsum
(R, FC1, FC2 and FC3), exposed to elevated temperature (200, 400, and 600° C) at ages (28days).
Table (3-1): The Density and Percentage Residual Density of Technical gypsum at elevated
Temperature
Temp.
ºC
Duration
Hour
Density of Technical gypsum Residual Density of gypsum
Volume fiber fraction (Vf )% Volume fiber fraction (Vf)%
R= 0% FC1=2% FC2=4% FC3=6% R=0% FC1=2% FC2=4% FC3=6%
40 - 1243 1226 1199 1220 100 100 100 100
200
0.5 1155 1125 1111 1094 93 92 93 92
1 1094 1077 1067 1050 88 88 89 88
400
0.5 1050 1037 1016 999 84 85 85 84
1 1026 1016 993 945 83 83 83 79
600
0.5 1016 1003 989 976 82 82 82 82
1 1020 979 986 965 82 80 82 81

Fig.(3-3) Effect of temperature on Density of
technical gypsum with different percentage of
cellulose fiber content at period of exposure
(0.5hr)
Also the results show the density of technical gypsum were decreased with increasing of
cellulose content at samples for different temperature and
(3-2) and Fig(3-5). The exposure of technical gypsum to high temperature leads to evaporation of
moisture unbound by hydrated compounds (free moisture) leaving voids in gypsum mass at below
temperature 130 ᵒC, after this the gypsum loses all its water of crystallization and
hydrate soluble gypsum or an hydrate un soluble
And the reason of decreasing of density due to increased the cellulose fibers content is the
took the portion of volume of gypsum,
pure technical gypsum (without fiber)
(gypsum + fiber).
C C- C- C- C-
Density(kg/m3)
Temp.- time (ᵒC-hr)
fiber
fiber
Fig.(3-1) Density of Technical Gypsum with
different percentage of cellulose fiber and
different temperature & period of exposure
Density(kg/m3)
Temperature (ᵒC)
16
3) Effect of temperature on Density of
cellulose fiber content at period of exposure
Fig.(3-4) Effect of temperature on Density of
cellulose fiber content at period of exposure (1hr
different temperature and period of exposure, as shown at Table
The exposure of technical gypsum to high temperature leads to evaporation of
gypsum loses all its water of crystallization and
gypsum or an hydrate un soluble gypsum [1] [3][16].
the reason of decreasing of density due to increased the cellulose fibers content is the
took the portion of volume of gypsum, and the density of cellulose fiber was lower than density of
pure technical gypsum (without fiber), in this case leads to reduction of total density of samples
C- C- C- C-
ResidualofDensity(%)
Temp.- time (ᵒC
fiber
fiber
C- C-
hr)
fiber
fiber
1) Density of Technical Gypsum with
different percentage of cellulose fiber and
different temperature & period of exposure
Fig.(3-2) The percentage of residual Density (with
respect to specimen at 40°C for mix R, FC1,
FC2and FC3)at 28 days
fiber
fiber
fiber
fiber
Density(kg/m3)
Temperature (ᵒ
4) Effect of temperature on Density of
ent at period of exposure (1hr)
as shown at Table
The exposure of technical gypsum to high temperature leads to evaporation of
turns out into an
the reason of decreasing of density due to increased the cellulose fibers content is the
fiber was lower than density of
this case leads to reduction of total density of samples
C- C-
C-hr)
fiber fiber
fiber fiber
2) The percentage of residual Density (with
respect to specimen at 40°C for mix R, FC1,
FC3)at 28 days
ᵒC)
fiber
fiber
fiber
fiber

Fig.(3
Density of technical gypsum of
temperature and period of exposure at28 days
Table (3-1): The residual percentage of
3-2-2 Compressive strength of Technical gypsum samples
The compressive strength is one of the most important properties of hardened gypsum.
Results reported in Table (3-3). It observed that compressive strength decreasing with increasing
temperatures. Fig.(3-6) shows the relation between compressive strengths and elevated temperature
for all specimens. While Table (3
strength values for the mixes of technical
600 ° C) at ages (28 days). It was found that:
Temp.
ºC
Duration
Hour
40 -
200
0.5
1
400
0.5
1
600
0.5
1
Density(kg/m3)
17
Fig.(3-5) Effect of cellulose fiber content on
Density of technical gypsum of different
temperature and period of exposure at28 days
The residual percentage of Density of ( FC1,FC2 and FC3) with respect R
2 Compressive strength of Technical gypsum samples
It observed that compressive strength decreasing with increasing
the relation between compressive strengths and elevated temperature
for all specimens. While Table (3-3) and Figs.(3-7), show the percentage residual compressive
technical gypsum, exposed to elevated temperature (200, 400,
600 ° C) at ages (28 days). It was found that:
Duration
Hour
Residual percentage of Density of
technical gypsum
Volume fiber fraction (Vf)%
FC1=2% FC2=4% FC3=6%
- 99 96 96
0.5 97 96 95
1 98 98 96
0.5 99 97 95
1 99 97 92
0.5 99 97 96
1 96 97 95
cellulose fiber content (%
C
C-
C-
C-
C-
C-
C-
Density of ( FC1,FC2 and FC3) with respect R
It observed that compressive strength decreasing with increasing
the relation between compressive strengths and elevated temperature
7), show the percentage residual compressive
gypsum, exposed to elevated temperature (200, 400, and

Table (3-3): The compressive strength and Percentage Residual compressive strength of Technical
gypsum at elevated Temperature
Temp.
ºC
Duration
Hour
compressive strength
Volume fiber fraction (
R=
0
%
FC1=2%
40 - 9.6 9
200
0.5 5.9 7
1 5 6.6
400
0.5 3.2 3.2
1 2.6 2
600
0.5 1.6 1.6
1 1.2 1.4
- For periods of exposure (0.5 and 1 hours) and at 200° C temperature, the percentage residual
compressive strength for technical
(98-91%) for mixes (R, FC1, FC2 and FC3) respectively.
- At 400 °C temperature and for periods of exposure (0.5 and 1 hours), the residual compressive
strength ranged between (33-27
and FC3) respectively.
- Raising the temperature to 600 °C caused some specimens have been destroyed
residual compressive strength
(22-23%) and (23-20%) for mixes
- For above the all specimens at ages 28 days compressive strength decreased with increasing
periods of exposure (0.5 and 1 hour) as shown in Table (
C C- C- C- C-
fcu(MPa)
Temp.- time (ᵒC-
fiber
fiber
Fig.(3-6) Compressive strength (fcu) of Technical
Gypsum with different percentage of cellulose fiber
and different temperature & period of exposure
18
Fig.(3-7) The percentage of residual Compressive
strength (fcu) (with respect to specimen at 40°C
for mix R, FC1, FC2and FC3)
The compressive strength and Percentage Residual compressive strength of Technical
gypsum at elevated Temperature
compressive strength of gypsum Residual compressive strength
Volume fiber fraction (Vf )% Volume fiber fraction (
FC2=4% FC3=6% R=0% FC1=2% FC2=4%
7.4 8.8 100 100 100
6.4 8.6 61 78 86
5 8 52 73 68
2.4 2 33 36 32
2.7 1.6 27 23 25
1.6 1.8 17 18 22
1.7 2 13 16 23
For periods of exposure (0.5 and 1 hours) and at 200° C temperature, the percentage residual
technical gypsum ranged between (61-52%), (78-73%),(86
FC2 and FC3) respectively.
At 400 °C temperature and for periods of exposure (0.5 and 1 hours), the residual compressive
27%), (36-23%), (32-25%) and (23-19%) for mixes
Raising the temperature to 600 °C caused some specimens have been destroyed
residual compressive strength of technical gypsum ranged between (17-13
for mixes (R, FC1, FC2 and FC3) respectively.
all specimens at ages 28 days compressive strength decreased with increasing
hour) as shown in Table (3-3) and Fig (3-8)& (3
C- C-
-hr)
fiber
fiber
C- C- C- C-
Residualfcu(%)
Temp.- time (ᵒC
strength (fcu) of Technical
Gypsum with different percentage of cellulose fiber
7) The percentage of residual Compressive
strength (fcu) (with respect to specimen at 40°C
for mix R, FC1, FC2and FC3)at 28 days
The compressive strength and Percentage Residual compressive strength of Technical
FC2=4% FC3=6%
100 100
86 98
68 91
32 23
25 19
22 20
23 23
For periods of exposure (0.5 and 1 hours) and at 200° C temperature, the percentage residual
73%),(86-68%) and
At 400 °C temperature and for periods of exposure (0.5 and 1 hours), the residual compressive
%) for mixes (R, FC1, FC2
Raising the temperature to 600 °C caused some specimens have been destroyed. The percentage
13%), (18-16%),
all specimens at ages 28 days compressive strength decreased with increasing
(3-9).
C- C-
C-hr)
fiber
fiber

Fig.(3-
compressive strength of gypsum of different
temperature and period of exposure at 28 days
It can be noticed that the compressive strength suffers a noticeable deterioration when
exposed specimens to elevated temperatures, it due to a lot of physical and chemical changes in
gypsum. Heating to a temperature of 200 °C does have
compressive strength of concretes, a small loss of strength was observed with comparison with
another temperature.
It was associated to an evaporation of free water as well as to an increasing in porosity of
the tested gypsum. This porosity increases due to expansion of the pore diameters, due to convert
the gypsum from phase (CaSO4.2H
increase in permeability. When temperatures reach above 200ºC, gypsum loses all
crystallization and turns out into an hydrate soluble gypsum. When we increase the heat
gypsum turns out into (an hydrated un soluble gypsum ) according Eq. (1
begin to dehydrate generating more water vapor and also
the compressive strength of technical gypsum in range of 300ºC and 600ºC [16]
that the color of specimens changed to gray, and color change increased when temperature and
the period of exposure increased. The induction of color change meaning loss in mechanical
properties.
Also the results indicate to the relation between steel fiber content and compressive
strength at elevated temperature are summarized in Table (3
exposure period. It was observed the compressive strength of fiber reinforced gypsum increases
with steel fiber content compared with plain gypsum at ages 28days and at temperature
(40,200 ᵒC)
It has been found that cellulose f
after exposure to elevated temperatures. cellulose fibers had been used to reduce the damage and
cracking due to high temperature for (FC1,
might be attributed to their bond to the matrix which can be enhanced by mechanical anchorage
or surface roughness[20].But at and 400
leads to burn the cellulose fiber and lost this benefit.
fcu(MPa)
19
-10) Effect of cellulose fiber content on
compressive strength of gypsum of different
gypsum. Heating to a temperature of 200 °C does have little significant effects on the
gypsum. This porosity increases due to expansion of the pore diameters, due to convert
.2H2O) to phase (CaSO4.1/2H2O)[1], and therefore leads to an
increase in permeability. When temperatures reach above 200ºC, gypsum loses all
crystallization and turns out into an hydrate soluble gypsum. When we increase the heat
gypsum turns out into (an hydrated un soluble gypsum ) according Eq. (1-2)[3] gypsum
begin to dehydrate generating more water vapor and also bringing about significant reduction in
the compressive strength of technical gypsum in range of 300ºC and 600ºC [16]
eased. The induction of color change meaning loss in mechanical
strength at elevated temperature are summarized in Table (3-4) & plotted in Figs.(3
It has been found that cellulose fibers improve the residual compressive strength of FCG
cracking due to high temperature for (FC1, FC2 and FC3) mixes at temperature (200
ibuted to their bond to the matrix which can be enhanced by mechanical anchorage
But at and 400 ᵒC and 600 ᵒC, the damage at gypsum was increased
leads to burn the cellulose fiber and lost this benefit.
cellulose fiber content (%)
C
C-
C-
C-
C-
C-
little significant effects on the
gypsum. This porosity increases due to expansion of the pore diameters, due to convert
and therefore leads to an
increase in permeability. When temperatures reach above 200ºC, gypsum loses all its water of
crystallization and turns out into an hydrate soluble gypsum. When we increase the heat the
2)[3] gypsum will
bringing about significant reduction in
the compressive strength of technical gypsum in range of 300ºC and 600ºC [16] . It is observed
eased. The induction of color change meaning loss in mechanical
4) & plotted in Figs.(3-10), for two
ibers improve the residual compressive strength of FCG
and FC3) mixes at temperature (200 ᵒC) This
ibuted to their bond to the matrix which can be enhanced by mechanical anchorage
C, the damage at gypsum was increased

20
Table (3-4): The residual percentage of compressive strength of (FC1, FC2 and FC3) with respect R
3-2-3 Flexural Strength of Technical gypsum
It can be seen that flexural strength decreased with increasing temperatures for all
specimens, as shown in Table (3-5) and Figs.(3-11). The percentage residual flexural strength is
summarized in Table (3-5) and Figs.(3-12), for mixes of SCC (R, FC1, FC2 and FC3), exposed
to high elevated temperature (200, 400 and 600° C) at ages 28 days. It was found that:
- The percentage residual flexural strengths ranged between (70-41%), (84-56%),(60-47%)
and (60-51%) for mixes (R, FC1,FC2 and FC3) respectively, at 200° C temperature and for
periods exposure (0.5 and 1 hours).
- At 400°C and 600°C temperature for periods exposure (0.5 and 1 hours) the residual flexural
strengths became zero, because all technical gypsum sample were cracked and destroyed by
heating.
- Flexural strengths decreased with increasing periods of exposure (0.5 and 1 hours), as shown
in Fig(3-13)(3-14) at all temperatures and at ages 28 days.
Table (3-5): The flexural strength and Percentage Residual flexural strength of Technical gypsum at
elevated Temperature
Temp.
ºC
Duration
Hour
Volume fiber fraction (Vf )% Volume fiber fraction (Vf)%
R=
0
%
FC1=2% FC2=4% FC3=6% R=0% FC1=2% FC2=4% FC3=6%
40 - 2 2.5 3 3.5 100 100 100 100
200
0.5 1.4 2.1 1.4 2.1 70 84 47 60
1 0.82 1.4 1.8 1.8 41 56 60 51
400
0.5 0 0 0 0 0 0 0 0
1 0 0 0 0 0 0 0 0
600
0.5 0 0 0 0 0 0 0 0
1 0 0 0 0 0 0 0 0
Temp.
ºC
Duration
Hour
The Residual percentage of
FC1=2% FC2=4% FC3=6%
40 - 94 77 92
200
0.5 119 108 146
1 132 100 160
400
0.5 100 75 63
1 77 104 62
600
0.5 100 100 113
1 117 142 167

It can be seen that flexural strengths decrease with high temperature as a result of the
shrinkage of technical gypsum cause decomposition
cracks inside specimens which reduces the flexural strengths
It was observed the flexural strength
cellulose fiber content compared with
Fig.(3-15)
Cellulose fiber reinforced gypsum have better
for mixes that exposed to 40 ᵒC and 200
crack resistance of the composite and to the ability of fibers to resist forces after the gypsum matrix
has failed. Also, the percentage of increase in flexural strength was found to be increased with the
increase in fiber content. This behavior is mainly attributed to the role of cellulose fibers in releasing
fracture energy around crack tips which is required to
one side to another side [21] as shown
It has been found that cellulose fibers improve the residual
exposure to elevated temperatures.
cracking due to high temperature for (FC1
might be attributed to their bond to the matrix which can b
or surface roughness [20]. But at and 400
leads to burn the cellulose fiber and lost this benefit as shown
C C- C- C- C-
fr(MPa)
fiber
fiber
Fig.(3-11) flexural strength (fr) of technical
gypsum with different percentage of cellulose fiber
21
can be seen that flexural strengths decrease with high temperature as a result of the
cause decomposition its compounds leading to the occurrence of
cracks inside specimens which reduces the flexural strengths [3] [16].
flexural strength of fiber reinforced gypsum increased with increasing
compared with plain gypsum at ages 28days, as shown in
Cellulose fiber reinforced gypsum have better to flexural strength than gypsum without fibers
C and 200 ᵒC temperature . This is mainly due to the increasing in
led. Also, the percentage of increase in flexural strength was found to be increased with the
fracture energy around crack tips which is required to extent crack growing by transferring it from
as shown Plate (3-1).
It has been found that cellulose fibers improve the residual flexural strength
exposure to elevated temperatures. Cellulose fibers had been used to reduce the damage and
cracking due to high temperature for (FC1, FC2 and FC3) mixes at temperature (200
might be attributed to their bond to the matrix which can be enhanced by mechanical anchorage
. But at and 400 ᵒC and 600 ᵒC, the damage at gypsum was increased
leads to burn the cellulose fiber and lost this benefit as shown Plate (3-2).
C- C-
hr)
fiber
fiber
C- C- C- C-
Residualfr(%)
Temp.- time (ᵒC
Fig.(3-12) The percentage of residual flexural
strength (fr) (with respect to specimen at 40°C for
mixes R, FC1, FC2and FC3)at 28 days
11) flexural strength (fr) of technical
can be seen that flexural strengths decrease with high temperature as a result of the
compounds leading to the occurrence of
of fiber reinforced gypsum increased with increasing
as shown in Table (3-6) and
to flexural strength than gypsum without fibers
This is mainly due to the increasing in
led. Also, the percentage of increase in flexural strength was found to be increased with the
extent crack growing by transferring it from
strength of FCG after
been used to reduce the damage and
and FC3) mixes at temperature (200 ᵒC) .This
e enhanced by mechanical anchorage
C, the damage at gypsum was increased
C- C-
ᵒC-hr)
fiber
fiber
fiber
12) The percentage of residual flexural
strength (fr) (with respect to specimen at 40°C for
mixes R, FC1, FC2and FC3)at 28 days

Fig.(3-13) Effect of temperature on flexural strength
(fr) of gypsum with different percentage of cellulose
fiber content at period of exposure (0.5hr)
Fig.(3
flexural strength (fr) of gypsum of different
Table (3-6): The residual percentage
Temp. ºC Duration Hour
40 -
200
0.5
1
400
0.5
1
600
0.5
1
fr(MPa)
Temperature (ᵒC)
fr(MPa)
22
fr(MPa)
Temperature (ᵒC)
13) Effect of temperature on flexural strength
of exposure (0.5hr)
Fig.(3-14) Effect of temperature on flexural strength
fiber content at period of exposure (1hr)
Fig.(3-15) Effect of cellulose fiber content on
flexural strength (fr) of gypsum of different
The residual percentage of flexural strength of (FC1, FC2 and FC3)
Duration Hour
Residual percentage of flexural strength
FC1=2% FC2=4% FC3=6%
125 150 175
150 100 150
171 220 220
0 0 0
0 0 0
0 0 0
0 0 0
fiber
fiber
fiber
fiber
C
C-
C-
C-
C-
C-
C-
ᵒC)
fiber
fiber
fiber
fiber
on flexural strength
nt at period of exposure (1hr).
FC2 and FC3) with respect R
flexural strength

23
Plate (3-1) Cellulose fibers used to decrease
cracks
Plate (3-2) Burn of cellulose fiber due to
heating above 400ᵒC temperature
3-2-4 Ultrasonic Pulse Velocity Results (U.P.V)
The results of ultrasonic pulse velocity test are listed in Table (3-7). The Figs.(3-16), shows
the relationship between pulse velocity and elevated temperature (200, 400 and 600°C), for all
specimens at two period of exposure . It was observed that pulse velocity decreases with increasing
temperatures. While Table (3-7) and Figs.(3-17), shown the percentage residual pulse velocity values
for the mixes of technical gypsum (R, FC1,FC2, and FC3), exposed to elevated temperature (200,
400 and 600°C) at ages 28 days). It was found that:
- For periods exposure (0.5 and 1 hour) and at 200°C temperature the percentage residual pulse
velocity for SCC ranged between (83-79%), (83-75%),(83-73%) and (81-68%) for mixes (R,
FC1, FC2 and FC3) respectively.
- The percentage residual pulse velocity for technical gypsum samples ranged between
(56-50%), (60-45%), (63-50%) and (61-46%) for mixes (R, FC1,FC2 and FC3) respectively, at
400°C and for periods exposure (0.5 and 1 hour).
- More reduction pulse velocity took place when the temperature increased to 600 °C. The
percentage residual pulse velocity for technical gypsum samples were (50-46%), (48-47%),
(48-44) and (43-43%) for mixes (R, FC1,FC2and FC3) respectively for periods of exposure
(0.5 and 1 hour).
- When specimens exposure to temperatures (200, 400 and 600°C) the pulse velocity showed
significant losses with increasing in periods of exposure (0.5 and 1 hours), at ages 28 days), as
shown Fig (3-18)(3-19).
It can be seen that the pulse velocity decreases with the temperature increases. Since the
exposure of concrete to high temperature leads to the evaporation of moisture unbound by the
hydrated compounds (free moisture) leaving voids behind in the concrete mass [22]. In addition, the
heating process leads to fine cracks resulting from volume changes. Also, the chemical and physical
effects of the heating process at higher temperature (dehydration of gypsum at about 200°C) [3], the
volume changes which play the main role in the cracking and deterioration of samples at high
temperatures. These voids retard the ultrasonic pulse leading to increase in the travel time and
consequently a decrease in the velocity[22].

Fig.(3-18) Effect of temperature on Ultrasonic Pulse
Velocity(UPV) of gypsum with different percentage of
cellulose fiber content at period of exposure (0.5hr)
Table (3-7): The UPV and Percentage Residual
Temp.
ºC
Duration
Hour
compressive strength of gypsum
Volume fiber fraction (
R=
0
%
FC1=2%
40 - 2.1 2.2
200
0.5 1.74 1.82
1 1.66 1.66
400
0.5 1.18 1.33
1 1.05 1
600
0.5 1.05 1.03
1 0.97 1.05
Fig.(3-16) Ultrasonic Pulse Velocity (UPV) of
C C- C- C- C-
UPV(km/sec)
fiber
fiber
UPV(km/sec)
Temperature (ᵒC)
24
18) Effect of temperature on Ultrasonic Pulse
at period of exposure (0.5hr)
Fig.(3-19) Effect of temperature on Ultrasonic Pulse
cellulose fiber content at period of exposure (
and Percentage Residual UPV of Technical gypsum at elevated Temperature
Volume fiber fraction (Vf )% Volume fiber fraction (
FC1=2% FC2=4% FC3=6% R=0% FC1=2% FC2=4%
2.2 2.35 100 100 100
1.82 1.9 83 83 83
1.6 1.6 79 75 73
1.38 1.43 56 60 63
1.11 1.08 50 45 50
0.97 1 50 47 44
1.05 1 46 48 48
Fig.(3-17) The percentage of residual Ultrasonic
Pulse Velocity (UPV) (with respect to sp
40°C for mix R, FC1, FC2and FC3)at 28 days
16) Ultrasonic Pulse Velocity (UPV) of
C- C-
hr)
fiber
fiber
f =
fiber
fiber
fiber
UPV(km/sec)
Temperature (ᵒC)
19) Effect of temperature on Ultrasonic Pulse
cellulose fiber content at period of exposure (1hr)
of Technical gypsum at elevated Temperature
Residual compressive strength
fraction (Vf)%
FC2=4% FC3=6%
100 100
83 81
73 68
63 61
50 46
44 43
48 43
17) The percentage of residual Ultrasonic
Pulse Velocity (UPV) (with respect to specimen at
40°C for mix R, FC1, FC2and FC3)at 28 days
C- C-
time (ᵒC-hr)
fiber fiber
fiber fiber
ᵒC)
f =
fiber
fiber
fiber

Fig.(3-20) Effect of cellulose fiber content on Ultrasonic
Pulse Velocity (UPV) of gypsum of different
The results indicated, the samples that
affected the ultrasonic pulse velocity at 40
Figs.(3-20). After this temperature (above 200
not clear, sometime the UPV increases and another decreased
4. CONCLUSIONS
According to the experimental results presented in the preceding above, temperatures do
affect the plain gypsum sample and fiber reinforced gypsum samples in a hardened state. On the
basis of the observations made in the present work, the following conclusions were fou
1. Overall, the workability and setting time decrease with the increase in cellulose fiber content
of the technical gypsum mixtures with respect to plain mixtures.
2. The residual density of technical gypsum
400 o
C and (82-80%) at 600 o
residual percentage of density of (FC1,
between (96-99%) at 40 o
C, (95
28 days.
3. The residual compressive strength ranged between (52
and (13-26%) at 600 o
C for mixes (R, FC1,
percentage of compressive strength
(R)ranged between (77-94%) at
167%) at 600 o
C at age 28 days.
4. The flexural strength was very sensitive to temperatures. Residual flexural strengths
between (41-84%) at 200 o
C, and became zero at 400
and FC3) at age (28 days), and the residual percentage of flexural strength of (FC1,
FC3) with respect to plain gypsum (R)
200 o
C and became zero at 400
5. The residual ultrasonic pulse velocity was ranged between (68
400 o
C and (43-50%) at 600 o
residual percentage of ultrasonic pulse velocity of (FC1,
UPV(km/sec)
25
20) Effect of cellulose fiber content on Ultrasonic
Pulse Velocity (UPV) of gypsum of different
, the samples that incorporating cellulose fibers in concrete positively
affected the ultrasonic pulse velocity at 40ᵒC and 200ᵒC temperatures, as shown in Table (3
fter this temperature (above 200 ᵒC), the role of cellulose fiber at gypsum sample was
, sometime the UPV increases and another decreased.
the experimental results presented in the preceding above, temperatures do
basis of the observations made in the present work, the following conclusions were fou
Overall, the workability and setting time decrease with the increase in cellulose fiber content
gypsum mixtures with respect to plain mixtures.
density of technical gypsum ranged between (93-88%) at 200
o
C for mixes (R, FC1, FC2 and FC3) at age (28 days), and the
residual percentage of density of (FC1, FC2 and FC3) with respect to plain gypsum (R)ranged
(95-98%) 200 o
C, (92-99%) at 400 o
C and (95- 99) at 600
The residual compressive strength ranged between (52-98%) at 200 o
C, (19
C for mixes (R, FC1, FC2 and FC3) at age (28 days), and the residual
percentage of compressive strength of (FC1, FC2 and FC3) with respect to plain gypsum
94%) at 40 o
C, (100-132%) 200 o
C, (62-104%) at 400
C at age 28 days.
The flexural strength was very sensitive to temperatures. Residual flexural strengths
C, and became zero at 400o
C and 600 o
C for mixes (R, FC1,
and FC3) at age (28 days), and the residual percentage of flexural strength of (FC1,
FC3) with respect to plain gypsum (R) ranged between (125-175%) at 40
and became zero at 400o
C and 600 o
C at age 28 days.
The residual ultrasonic pulse velocity was ranged between (68-83%) at 200
o
C for mixes (R, FC1, FC2 and FC3) at age (28
residual percentage of ultrasonic pulse velocity of (FC1, FC2 and FC3) with respect to plain
C
C-
C-
C-
C-
C-
C-
incorporating cellulose fibers in concrete positively
C temperatures, as shown in Table (3-8) and
, the role of cellulose fiber at gypsum sample was
the experimental results presented in the preceding above, temperatures do
basis of the observations made in the present work, the following conclusions were found:
Overall, the workability and setting time decrease with the increase in cellulose fiber content
88%) at 200 o
C, (85-79%) at
FC2 and FC3) at age (28 days), and the
FC2 and FC3) with respect to plain gypsum (R)ranged
99) at 600 o
C at age
C, (19-36%) at 400 o
C
FC2 and FC3) at age (28 days), and the residual
FC2 and FC3) with respect to plain gypsum
104%) at 400 o
C and (100-
The flexural strength was very sensitive to temperatures. Residual flexural strengths ranged
C for mixes (R, FC1, FC2
and FC3) at age (28 days), and the residual percentage of flexural strength of (FC1, FC2 and
0 o
C, (100-120%)
83%) at 200 o
C, (45-63%) at
FC2 and FC3) at age (28 days), and the
FC2 and FC3) with respect to plain

26
gypsum (R)ranged between (105-112%) at40 o
C ,(96-109%) 200 o
C , (95-121%) at 400 o
C and
(92-108%) at 600 o
C at age 28 days .
6. Deterioration in strength increases with increases in periods of exposure to elevated
temperatures for all mixes.
7. Cracking and Spalling occur when specimens are exposed to high temperatures at 400 o
C and
for long period of exposure. .
8. The optimum fiber content was (2% by Vol.) improves hardened properties against the high
temperatures.
9. The cellulosic fiber helped to improve the flexural strength of gypsum samples at 40 ᵒC and
200 ᵒC and improvement the compressive strength gypsum samples at 200 ᵒC.
REFERENCE
[1] Duggal S.K., "Building Materials", Third Revised Edition, New Age International Publishers,
New Delhi, 2008, pp.(458-466).
[2] Raof Z.M., "Fibrous Plaster Boards", Iraqi Industrial Union, Consulting Corp for construction
Industries, August 1996.
[3] AL-Ameeri A.S., "Building Materials", Lectures of Building Materials, First Stage, Civil
Engineering ,Babylon university, 2007.
[4] British Standard Institution, BS 1191 Part1 -1973, "Specification of Gypsum Building
Plasters.
[5] Central Organization for Standardization & Quality Control, Iraqi Standard, IQS 28-1988,
"Building Gypsum".
[6] Faiyadh, F.I., Mahmood, D.B.A. and Khalaf, F.M., "Proposals in Improvement the Pure
Iraqi-Gypsum properties", Journal of Building Research, Vol.6, No.2, 1987.
[7] Al-Taee M.H., "Improvement of properties of gypsum private sector produced from
Secondary Gypsum at Center and South of Iraq", Journal of Building Research, Vol.7, No.1,
1988.
[8] Al-Aubaidi L.S., "Improvement of properties of gypsum by Using Additive Materials", M.Sc.
Thesis, Building and Construction Department, University of Technology, 2007.
[9] Al-Qaisi W.A., "Some of the effect of chemical additives on the Setting time for Iraqi
technical Gypsum ", Journal of Engineering and Development, Vol.23, No.1, 2004.
[10] Fraih K.J, Al-Qaisi W.A. Abdul Khaliq L.S., "The Effect of Some Natural Admixtures on the
Setting Time of Iraqi Plaster of Paris", Journal of Engineering and Development, Vol.24,
No.9, 2005.
[11] Al-Sudani, M. A., "The Use of Gypsum Materials as a substitutes in Building and Finishing
Work", M.Sc. Thesis, Building and Construction Department, University of Technology,
2001. .
[12] Al-Ramadhani K.A., "Gypsum products, ceramic and marble materials Light", Building
Symposium, Baghdad, 1994.
[13] AL-Baghdadi A.A., " Improvement of Mechanical properties for Juss Mortar Using vegetable
and their plants Fibers", Technology Journal, Vol.23, No.1,2010.
[14] AL-Naiemi Y.H., "Gypsum Boards Reinforced with Cellulose Fibers", M.Sc. Thesis, Civil
Department, University of Baghdad.
[15] Iraqi Ministry of Construction and Housing, Iraqi Building Code 405 -, "Protect buildings
from fire", 2014.
[16] Muhammed S. M., "Residual Compressive Strength of Iraqi-Gypsum Subjected to Elevated
Temperature Exposure ", Journal of Babylon University, Vol.18, No.5, 2010.

27
"Chemical Test of Gypsum for Building Purposes".
"Physical Test of Gypsum for Building Purposes".
"Determine Ultrasonic Pulse Velocity in Concrete".
[20] Sawamy R.N., "New Reinforced Concrete", Surrey University Press, 1985.
[21] Teng Y.S. and Shah S.P., "Crack Propagation in Fiber Reinforced Concrete", Journal of
Structural Engineering, Vol. 112, No. 1, (1986), pp.(19-34).
[22] Hassan, S. A., "Effect of High Elevated Temperature on the Compressive Strength and
Ultrasonic Pulse Velocity of High Strength Concrete", Journal of Engineering and
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[23] Abbas S. Al-Ameeri, K.A.Al- Hussain and M.S Essa, “Constructing a Mathematical Models
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[24] Alaa Abdul Kareem Ahmad, “The Effect of Gypsum Compensative on Mortar Compressive
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[25] Abbas S. Al-Ameeri and Rawaa H. Issa, “Effect of Sulfate on the Properties of Self
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