Behavior immersion of phosphogypsum crushing sand based bricks

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 4, May – June (2013), © IAEME
96
BEHAVIOR IMMERSION OF PHOSPHOGYPSUM- CRUSHING SAND
BASED BRICKS
Lamia Bouchhima(1), Mohamed Jamel Rouis (2), Mohamed Choura (3)
Unit of research environmental geotechnique and civil materials, Institute of the engineers of
Sfax, Tunisia
Affiliation and address: Institute of the engineers of Sfax, road Sokra, Km3.5, B.P1173-3038
Sfax, Tunisia
ABSTRACT
A feasibility study was undertaken on the production of crushing sand-natural
hydraulic lime-cement-phosphogypsum (CS-NHL-C-PG) full bricks to build houses
economically by utilizing industrial wastes. All full bricks were made on a bench model,
semiautomatic press having a capacity of 25 tons, as shown in appendix, to produce bricks of
51×95×203 mm in size under a static compaction of 20MPa.
The compressive strength, flexural strength water absorption and density of these bricks are
investigated. It is observed that these bricks have sufficient strength for their use in low cost
housing development. Tests were also conducted to study behavior immersion of
phosphogypsum- crushing sand based bricks. The results suggest that these bricks have
sufficient behavior immersion.
Keywords: Phosphogypsum; crushing sand; strength; immersion
1. INTRODUCTION
There is a general exodus of rural population to the cities with the rapid industrialization
in developing countries. The infrastructure to support these cities, such as buildings for
housing and industry, mass transit for moving people and goods, and facilities for handling
water and sewage will require large amounts of construction materials. Enhanced
construction activities, shortage of conventional building materials and abundantly available
industrial wastes have promoted the development of new building materials.
INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN
ENGINEERING AND TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 4, Issue 4, May – June 2013, pp. 96-106
© IAEME: www.iaeme.com/ijaret.asp
Journal Impact Factor (2013): 5.8376 (Calculated by GISI)
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IJARET
© I A E M E

97
Phosphogypsum is an important by-product of phosphoric acid fertilizer industry. It
consists of CaSO .2H O 4 2 and contains some impurities such as phosphate, fluoride,
organic matter and alkalies. In Tunisia, for several years, a set of phosphoric acid production
factories have produced PG in large great quantities (approximately 10 million tons per year
[1]. Currently, the PG is stored into piles in the vicinity of the factory, by dry or wet process.
The storage of PG causes the pollution of the water table and the soils by acid and heavy
metals infiltrations.
Its valorization leads to environmental protection and to minimization of the storage
costs. Several researchers had studied the use of PG in various fields. The PG was treated to
be used in the plaster manufacture. It has been found that the PG is suitable for making good
quality plaster showing similar proprieties to natural gypsum plaster [2-4]. This field is
advantageous for the countries which do not have natural quarries such as Japan and India.
The PG has been sought also to be used in agriculture [5]. It is as effective as the crushed
natural gypsum. However, the quantities used are limited and moreover the health standards
became increasingly restrictive. But the most interesting use of the PG is for the cement
manufacturing: either by natural gypsum substitution (about 5%), which will play the role of
a set retarder [6-7], or to reduce the clinkerization temperature [8]. The PG was also used in
soil stabilization [9]. Finally phosphogypsum PG has been studied to be used in hollow
blocks [10] and light brick [11].
In Tunisia, the PG was studied to be used in similar fields. The most successful
application so far is in the manufacture of cement; by substitution of the gypsum. The
obtained product is known under the name of cement ultimo. It showed good performances
but the used quantity is low [12-13]. Moussa et al [14] had studied the possibility of the use
of the PG in the embankments. The PG is studied in order to use it like a fill. This study
showed a behavior to the compaction not similar to that of a soil. Furthermore, the fill
showed also a continuous settlement because of the PG solubility. Moreover, Kuryatnyk and
Angulski- Ambroise- Pera [15] have employed the Gabes and Skhira PG to be used as a
hydraulic binder. But formation of ettringite led to cracking and strength loss. Finally, Sfar
[16] has explored the PG for a road use. The study proposed the following formulation:
46.5% of PG, 46.5% of sand and 7% of cement. But this study was conducted in the Tunisian
south region, where the rainfall is low.
In this paper, at first, compressive strength, flexural strength water absorption and
density of phosphogypsum- crushing sand-lime-cement bricks grade NW are investigated.
The second part deals with the Behavior immersion of phosphogypsum- crushing sand based
bricks
2. EXPERIMENTAL PROGRAM
2.1.Chemical composition
The chemical analyses, considered most relevant to the prospect use in commercial
brick making, were undertaken on the PG. The results of these analyses are presented in
Table 1. The PG is primarily (about 77%) made up of calcium sulfate (CaSO4). The
remaining components are present at low percentage. It should be noted that the pH of PG
samples has been found to be around 2.9, indicating a high acidity of the PG.

98
Table1. Chemical composition of phosphogypsum
Elements (%)
CaO SO3 P2O5 F SiO2 Fe2O3 Al2O3 MgO
Ignition
loss at
1000°C
32.8 44.4 1.69 0.55 1.37 0.03 0.11 0.007 22.3
2.2. Grain density
The real densities of the grains were determined by the pycnometer method, by using
water saturated with gypsum. The studied PG presents a density of about 2300 kg/m3. The
real densities of the grains were determined by the pycnometer method. The studied crushing
sand presented a density of about 2740 kg/m3 kg/m3. This value is higher than the one for
phosphogypsum.
2.3. Application of Phosphogypsum in the solid brick
2.3.1. Mix proportion
In the present study, a low slump mix was used to limit the shrinkage. The water contents of
Phosphogypsum-crushing sand-lime mixtures were fixed respectively to 4 %. Bricks
produced with more than 5 % showed cracks after fabrication due to excessive water.
The mix proportions of phosphogypsum, crushing sand (CS), lime and cement (cement HRS
42.5) for bricks are given in table 2. The mix proportions are given in terms of dry weights of
the ingredients.
Table 2 Mix proportions of CS-NHL-C-PG full bricks
Mix désignation
Constituant materials (Weight %)
Phosphogypsum Sand (CS) Cement Lime
P-1 60 33 5 2
P-2 60 30.5 7.5 2
P-3 60 28 10 2
P-4 70 23 5 2
P-5 70 20.5 7.5 2
P-6 70 18 10 2
P-7 80 13 5 2
P-8 80 10.5 7.5 2
P-9 80 8 10 2
2.3.2. Manufacturing process
2.3.2.1 Mixing of raw materials
A mixer is used for mixing materials. The dry phosphogypsum was sieved through 1
mm sieve. The weighed quantity of phosphogypsum, crushing sand, lime and cement were
first thoroughly mixed in dry state for a period of 10 minutes to uniform blending. The
required water was then gradually added and the mixing continued for another 5 min.

99
2.3.2.2. Preparation of bricks
All full bricks were made on a bench model, semiautomatic press having a capacity of
25 tons, as shown in appendix, to produce bricks of 51×95×203 mm in size under a static
compaction of 20MPa.
2.3.2.4. Testing of bricks
All bricks were dried to the free air for a period of 28, 56 and 90 days. Compressive
strength, density, water absorption and leaching tests of bricks from different mixes of
phosphogypsum, sand, lime and cement with available mixing water content were
determined.
Compressive strength of the units was determined according to ASTM C67 [17]. Test
bricks consist of a half brick with full height and width. Flexural strength tests on the bricks
were performed according to ASTM C 67 [17]. Test specimens were taken as full-size brick
units.
The absorption qualities of brick are taken as a part of the acceptance measurement of
the durability of the material. ASTM specification C67 describes a method by which
absorption of building clay brick can be measured. First, the samples are immersed for 24
hours in cold water. The amount of water absorbed is then recorded as a percentage of the
total weight of the dry unit.
In order to determine the density of each brick, dry bricks were weighed accurately
and their volumes were measured.
To simulate the action of the weather, the bricks are soaked in water for two days
[18]. After 90 days of treatment. In this work the effect of immersion on compressive
strength and flexural strength have been studied.
The leaching tests had been performed according to the French norm NF EN 12457-3
[19] at an ambient temperature (20 ± 5°C). The specimens (three different samples for each
mix-design) were crushed and an amount of 0.175 kg was taken to be analyzed. The distilled
water was added to obtain a liquid/solid ratio of 10 l/kg.
The compressive and flexural strength and speed of sound of phosphogypsum-based
bricks were tested after 28, 56 and 90 days of curing. Water absorption, density, and leaching
test were determined on bricks tested after 28 days of casting.
3. TEST RESULTS AND DISCUSSION
3.1. Dry density
The densities of CS-NHL-C-PG full bricks are shown in table 3. These densities range
from 1523 to 1670 kg/m3
. Therefore the CS-NHL-C-PG full bricks have high density.
Table 3.Dry densities (kg/m3
) of CS-NHL-C-PG full bricks
Dry densities (kg/m3
)
M1 M2 M3 M4 M5 M6 M7 M8 M9
1535 1564,5 1594 1570 1606 1642,5 1633 1670 1751,5
3.2.The 24-h cold water absorption of studied bricks
The water absorption is a principal factor for the durability of the product and its
behavior to natural environment. Table 4 presents the results of the water absorption for the
selected percentages of the bricks. It was observed that the water absorption of bricks

100
decreased with the increase cement contents. Also, it was observed that the values obtained
were favorable when compared with those of clay bricks (0 to 30%) [20].
Table 4 .Water absorption of CS-NHL-C-PG full bricks
Mix designation Water absorption after 24
hr cold water (%)
M1 24.65
M2 23.78
M3 22.02
M4 23.3
M5 22.07
M6 21.46
M7 21.52
M8 20.7
M9 19
3.3. Compressive strength of studied bricks
The results, obtained as an average of measurements performed on three specimens,
are shown in table 5. The BS6073-Part 1 standards [21] require minimum compressive
strengths of 7.0 MPa and 11.7 MPa after a 28-day curing period for load-bearing concrete
masonry units. All of the 28-day-cured mixtures described in this study satisfied the BS6073
[21] standard for compressive strength.
For all the studied cases, the strength of the 90 days cured full bricks was higher than
10.3 MPa, which is the minimum strength indicated by the standards [22]. Cement and lime
as a source of reactive silica and alumina are given to silicate and aluminate hydrates, which
are responsible for the development of strength.These Figures show also increase in the
strength with the cement additions. This result confirms the water absorption test outcome,
where it has been indicated that the addition of cement produces a decrease in the internal
pore size. Thus, the brick becomes less porous causing an increase in the mechanical
strength.
Table 5. Compressive strength of CS-NHL-C-PG full bricks
Mix designation Compressive strength
(MPa)
(28 days)
Compressive strength
(MPa)
(56 days)
Compressive strength
(MPa)
(90 days)
M1 12.48 13.568 13.956
M2 13.947 14.79 15.1
M3 14.746 15.361 15.553
M4 13.4 14.531 14.8
M5 14.213 15.228 15.493
M6 15.669 16.269 16.462
M7 13.9 14.79 15.22
M8 14.676 15.703 16.2
M9 16.034 16.887 17.3

0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue
3.4. Flexural strength of studied bricks
The results, obtained as an average of measurements performed on thr
are shown in table 6. The code ASTM does not specify a requirement for flexural strength.
However the values obtained were f
strength required by BS6073-Part 1 (0.65 MPa) after a 28
surpassed by all the samples.
Table 6.Flexural strength of CS
Mix designation flexural strength
(MPa)
(28 days)
M1 7.712
M2
M3
M4 7.895
M5
M6
M7
M8
M9
3.5. Behavior immersion of bricks
3.5.1. Compressive strength of full bricks after 2 days immersion
are shown in Figs. 1-3. The loss of
given in table 7. It is observed that loss in compressive strength decrease with
phosphogypsum and cement content. So bricks with more phosphogypsum and cement have
better compressive strength after 2 days immersion
Figure.1 compressive strength of CS
0
2
4
6
8
10
12
14
16
compresive
strength
(MPa)
6499(Online) Volume 4, Issue 4, May – June (2013), © IAEME
101
strength of studied bricks
The code ASTM does not specify a requirement for flexural strength.
However the values obtained were favorable when compared with the minimum flexural
Part 1 (0.65 MPa) after a 28-day curing period [21] wich
Flexural strength of CS-NHL-C-PG full bricks
flexural strength
(MPa)
(28 days)
flexural strength
(MPa)
(56 days)
flexural strength
(MPa)
(90 days)
7.712 8.13 8.25
8 8.35 8.505
8.12 8.7
7.895 8.332 8.44
8.16 8.5 8.604
8.51 8.82
7.9 8.332 8.499
8.27 8.7 8.887
8.56 8.913 9.001
of bricks
Compressive strength of full bricks after 2 days immersion
. The loss of compressive strength after 2 days of immersion in water is
t is observed that loss in compressive strength decrease with
compressive strength after 2 days immersion.
ressive strength of CS-NHL-C-PG full bricks (phosphogypsum=60%)
5 7.5 10
cement (%)
CS
CSi
June (2013), © IAEME
ee specimens,
The code ASTM does not specify a requirement for flexural strength.
avorable when compared with the minimum flexural
[21] wich was
flexural strength
(MPa)
(90 days)
8.25
8.505
8.8
8.44
8.604
8.9
8.499
8.887
9.001
immersion in water is
t is observed that loss in compressive strength decrease with
PG full bricks (phosphogypsum=60%)
CS
CSi

Table 7. Loss in compressive s
mixe M1 M2
Loss in
compressive
strength (%)
10.6 8.4
0
5
10
15
20
compressive
strength
(MPa)
0
5
10
15
20
compressive
strength
(MPa)
102
compressive strength of CS-NHL-C-PG full bricks (phosphogypsum=70%)
compressive strength of CS-NHL-C-PG full bricks (phosphogypsum=80%)
Loss in compressive strength of CS-NHL-C-PG full bricks
M3 M4 M5 M6 M7 M8
7.1 10 7.9 6.5 9.4 7.1
5 7.5 10
cement (%)
CS
CSi
5 7.5 10
cement (%)
CS
CSi
PG full bricks
M8 M9
7.1 5.9
CS
CSi
CS
CSi

3.5.2. Flexural strength of full bricks after 2 days immersion
The results, obtained as an average of mea
shown in Figs. 4-6. The loss of flexural strength after 2 days of immersion in water is given
in table 8. It is observed that loss in flexural strength decrease with phosphogypsum and
cement content. So bricks with more phosphogypsum and cement have better behavior to
immersion in water.
Figure.4 Flexural strength of CS
0
2
4
6
8
10
flexural
strength
(MPa)
0
2
4
6
8
10
flexural
strength
(MPa)
103
Flexural strength of full bricks after 2 days immersion
The results, obtained as an average of measurements performed on three specimens, are
. The loss of flexural strength after 2 days of immersion in water is given
is observed that loss in flexural strength decrease with phosphogypsum and
th more phosphogypsum and cement have better behavior to
Flexural strength of CS-NHL-C-PG full bricks (phosphogypsum=60%)
Flexural strength of CS-NHL-C-PG full bricks (phosphogypsum=70%)
5 7.5 10
cement (%)
FS
FSi
5 7.5 10
cement (%)
FS
FSi
surements performed on three specimens, are
. The loss of flexural strength after 2 days of immersion in water is given
is observed that loss in flexural strength decrease with phosphogypsum and
th more phosphogypsum and cement have better behavior to
FS
FSi
FS
FSi

Table 8. Loss in flexural strength of CS
mixe M1 M2 M3
Loss in
flexural
strength
(%)
11.6 8.49 7.6
3.6. Leaching tests
The average values of the leachi
the selected metal species, i.e., Cd, Cu, Zn, Ni, Pb, and Cr, for
below the regulatory limits. Thus, this result indicates that PG amended brick speci
be considered as non hazardous materials.
Table 9.Leaching test results, in mg/kg for L/S = 10 l/kg
Eléments M1 M2 M3 M4
Cr 0.058 0.055 0.14 0.
Ni 0.055 0.05 0.04 0.046
Zn 0.036 0.034 0.032 0.032
Pb 0.085 0.08 0.078 0.081
Cu 0.095 0.085 0.083 0.08
Cd 0.05 0.047 0.042 0.04
0
2
4
6
8
10
flexural
strength
(MPa)
104
rength of CS-NHL-C-PG full bricks (phosphogypsum=80%)
Loss in flexural strength of CS-NHL-C-PG full bricks
M3 M4 M5 M6 M7 M8
7.6 8.2 7.3 6.4 6.2 4.5
age values of the leaching test are presented in Table 9. The concentrations of
the selected metal species, i.e., Cd, Cu, Zn, Ni, Pb, and Cr, for all mix-design, were well
the regulatory limits. Thus, this result indicates that PG amended brick speci
be considered as non hazardous materials.
Leaching test results, in mg/kg for L/S = 10 l/kg
M4 M5 M6 M7 M8 M9
Limit
values
acceptable
as inert
0.048 0.045 0.037 0.035 0.026 0.02 4
0.046 0.041 0.033 0.041 0.039 0.035 0.4
0.032 0.03 0.029 0.028 0.026 0.024 4
0.081 0.079 0.077 0.078 0.077 0.075 0.5
0.08 0.082 0.079 0.078 0.076 0.069 2
0.04 0.02 0.01 0.025 0.01 0.01 0.04
5 7.5 10
cement (%)
FS
FSi
M8 M9
4.5 4
The concentrations of
design, were well
the regulatory limits. Thus, this result indicates that PG amended brick specimens can
Limit
values
acceptable
as inert
Limit
values
acceptable
as non
hazardous
50
10
50
10
50
1
FSi

105
4. CONCLUSION
Based on the experimental investigation reported in this paper, following conclusions
are drawn:
(1) The CS-NHL-C-PG bricks have sufficient strength and have potential as a replacement
for load-bearing concrete masonry units.
(2) The increase of the percentages of PG and cement resulted in increase in the compressive
and flexural strength of full bricks after 2 days of immersion in water.
(3) Cementations binder with 80% phosphogypsum content shows low loss of compressive
and flexural strength after immersion.
(4) Loss of flexural strengths is lower than those of compressive. Therefore the bricks
immersed in water perform better in flexure than in compression.
(5) All full bricks specimens can be considered as non hazardous materials.
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