Abstract number: Paper 171
RESISTANCE OF CONCRETE MIX WITH BLAST
FURNACE SLAG TO SULFATE AND ACID ATTACK
B. G. Buddhdeva, Ph-9427731921, Email: [email protected]
Dr. H. R. Variab, Ph-9426561104, Email: [email protected]
Corresponding author: B. G. Buddhdeva, Ph-9427731921, Email: [email protected]
a
Research Scholar, R. K. University, Rajkot & Lecturer, Civil Engineering Department, Govt. Polytechnic,
Rajkot (Gujarat).
b
Principal, Tatva Institute of Technological Studies, Modasa, Dist: Aravalli (Gujarat)
Abstract:
This paper presents the study carried out on concrete mix with blast furnace slag (BFS) as full replacement of
fine aggregates (sand) under sulfate and acid attack. Both types of concrete mix with BFS and control concrete
made from ordinary portland cement (OPC) have been subjected to 5% sodium sulfate and magnesium sulfate
as well as 0.5%, 1%, 2% of sulphuric acid solution. Then results are compared with control concrete. From the
results, it is revealed that concrete mix with BFS undergoes very less change in compressive and flexural
strength, as well as change in mass. Hence, durability under acid and sulfate attack of concrete mix with BFS is
much superior as compared to control concrete, which suggests its good applicability in field especially for
coastal area construction.
Keywords: Blast Furnace Slag, Concrete, Sand (Fine Aggregate), Sulfate, Sulphuric Acid
1. Introduction:
Concrete is acceptable and trusted material in the construction industry for many years. It has so many
applications and utilization in the construction industry for various applications. Since the progress of any nation
is measured by its infrastructure growth, this demand is going to increase exponentially. The popularity of
concrete as construction material is due to its excellent mechanical properties, mould ability, adaptability,
relatively good fire resistance capacity and availability. It is most intriguing material which can be reasonably
engineered to satisfy given criteria within certain boundary limits [1]. In the era of sustainable and green
technology, concrete material also came across new innovation and technological development in a form of
varieties of waste material utilization to produce the concrete. Out of many waste materials available, blast
furnace slag (BFS) is one of them. Blast furnace slag, which is a by-product of iron making process, is a glassy
material with an amorphous structure, pozzolanic properties and sand-to-gravel-size particles [2]. Due to huge
amount of production of BFS, stockpiling and land filling are major environmental issues for this waste material
[3]. Most of the time, BFS is used as a partial replacement of coarse aggregate in manufacturing of concrete for
different purposes. At very few instant, BFS is utilized as partial replacement of sand as fine aggregates in the
production concrete. Apart from above information, utilization of blast furnace slag in India is very limited in
comparison with abroad. On the other hand; in the production of concrete, one of the important ingredients is
the fine aggregate (sand) available from natural river beds. Due to current environmental condition, the
availability of quality sand for production of the concrete is very much difficult. Eventually, guidelines for
utilization of this slag are not available in any BIS codes, IRC publication or any other reputed organization’s
publication in context with this topic. This situation is responsible for under utilization of BFS in production of
concrete especially in India. To bridge this research gap it is essential to develop some guidelines as well as
technical information related to BFS as well as to know effect of this material for full replacement in concrete
production rather than partial replacement without adding other cementatious materials. The basic aim of Treaty
of Rome is directed towards the prevention, reduction and elimination of environmental damage either at source
or by careful management of natural resources [4]. To support the aim of Treaty of Rome, the utilization of BFS
as full replacement of sand in production of concrete is one of the innovative concept.
In this paper, a comprehensive experimental program is undertaken to evaluate the resistance against sulfates
and acid attack by control concrete and concrete mix with BFS. Effect of sodium and magnesium sulfate as well
as sulfuric acid on various parameters like change in mass, compressive and flexural strength of concrete are
evaluated. Comparative study between control concrete and concrete mix with BFS for these parameters are
made. The analysis in this study has shown the superior resistance by concrete mix with BFS as compared with
control concrete. These results are also indicative of utilization of BFS in production of concrete which can be
utilized in off shore construction as well as in some acidic prone zone. Ultimately, concrete mix with BFS is
capable of meeting the performance criteria in construction industry [5].
2. Objective of Research Study:
The objective of this paper is to study the resistance against sulfate and acid of concrete mix with BFS when
fine aggregate is fully replaced with BFS in production of concrete. This study is assessing feasibility criteria of
utilization of BFS in off shore and costal area construction by comparative study of various parameters. The
study also helps in promoting utilization of such waste material in concrete, thus saving in the natural resources
and provides solution to the environmental problem due to dumping of such waste material.
3. Experimental Programme:
3.1 Materials Used:
Cement:
OPC 53-grade satisfying the requirements of IS: 12269 having Specific Gravity-3.15, Fineness- 3.25% on 90μ
IS sieve has been considered [6].
Fine aggregate:
Locally available sand from river Bhadar, Rajkot, India passing through 4.75 mm IS sieve. It is clean and free
from impurities having Specific Gravity-2.59, Water absorption-0.4%, Fineness modulus (F. M.)-2.85 and
confirming to zone-I as per IS:383-1970 has been used[7].
Coarse aggregate:
Locally available angular crushed stone of control size 20 mm down confirming to IS: 2386-1963 having
Specific Gravity-2.77, Water absorption-0.6% and Fineness modulus (F. M.)-7.18 have been selected for
investigation [8].
Material passing, %
Blast Furnace Slag:
Air cooled blast furnace slag obtained from industrial area of Rajkot city, Gujarat (India) of Size-4.75 mm down
up to 150 micron (i.e. as fine aggregate) having gradation shown in fig. 3.1, Specific Gravity-2.72, Water
absorption-1.35%, Fineness modulus (F. M.)-2.82 and confirming to zone-I as per IS:383-1970 has been
selected. Table 3.1 shows the chemical properties of blast furnace slag used in the study [7].
120
100
80
60
40
20
0
Slag gradation
UL of IS
LL of IS
0.1
1
10
Sieve opening, mm
Figure 3.1: Gradation of blast furnace slag [9]
Table 3.1: Chemical Properties of Blast Furnace Slag [10]
Chemical Properties of BFS
in %
CaO
26.5
SiO2
34.0
Al2O3
17.25
MgO
7.0
Fe2O3
18.25
SO3
0.5
Water:
Ordinary tap water is used for both mixing and curing of concrete specimens.
Concrete Mix [11, 12]:
The method of mix design in IRC: 44-2008 has been employed to design the mix for M40 grade of concrete.
These design mix is prepared both for sand in control concrete and BFS in concrete with BFS as fine aggregates.
The details of design mix for 1 cubic meter of concrete produced is shown in Table-3.2 and Table-3.3 for M40
grade of concrete selected with sand and BFS as fine aggregates respectively. The appropriate dosage of super
plasticizer of Sikka make is utilized for normal slump value of 25 mm for concrete mix to achieve desire
strength & workability, which is required for higher grade of concrete like M40.
Table 3.2: Mix proportions for 1 cubic meter of concrete with sand
Grade of concrete
Cement (Kg)
Sand (Kg)
M40
416
694
Coarse aggregates (Kg)
10mm down
20 to 10mm
484
725
Water (Kg)
Admixtures (Kg)
168
2.5
Table 3.3: Mix proportions for 1 cubic meter of concrete with BFS
Grade of concrete
Cement (Kg)
BFS (Kg)
M40
416
684
Coarse aggregates (Kg)
10mm down
20 to 10mm
498
750
Water (Kg)
Admixtures (Kg)
175
2.5
3.2 Sulfate Resistance: [5]
The durability of concrete is defined as its ability to resist weathering action, chemical attack, abrasion, or any
other process of deterioration. Sulfate resistance for concrete with BFS is one of the important parameter need to
address for the durability concern. The test specimens 150 mm x 150 mm x 150 mm cubes and 100 mm x 100
mm x 500 mm beams were casted for test. Cubes and beams were immersed in 5% sodium sulfate solution &
magnesium sulfate solution after 28 days of curing period for the exposure period of 7, 28 & 91 days. [13] The
sulfate resistance is evaluated based on the change in mass and change in compressive as well as flexural
strength of the specimen after the different period of sulfate exposure. Change of mass is evaluated by taking
weight of the specimen before the immersion in sulfate solution and taking weight after the each exposure
period i.e. 7, 28 & 91 days. % change in mass is calculated. Similarly change in compressive and flexural
strength is evaluated for both types of sulfate solution for each exposure period i.e. 7, 28 & 91 days.
Comparative plots are prepared for concrete with sand and BFS.
3.3 Acid Resistance: [5]
There is no standard test for acid attack on concrete and thus resistance to acid attack in this investigation is
tested by immersion of concrete specimens with BFS in a solution of sulfuric acid.[14,15] The concentrations of
sulfuric acid solution are taken as 2%, 1% and 0.5%. The test specimens 150 mm x 150 mm x 150 mm cubes
and 100 mm x 100 mm x 500 mm beams are casted for test. Cubes and beams are immersed in 2%, 1% and
0.5% sulfuric acid solution after 28 days of curing period for a specific exposure period of 7, 28 and 91 days.
The acid resistance is evaluated based on the change in mass and change in compressive as well as flexural
strength of the specimen for various concentration of sulfuric acid exposure. Change of mass is evaluated by
taking weight of the specimen before the immersion in sulfuric acid solution of various concentrations and
taking weight after the each exposure period i.e. 7, 28 & 91 days. % change in mass is calculated and
comparative plots are prepared for concrete with sand and BFS. Similarly change in compressive and flexural
strength is evaluated for various concentration of sulfuric acid solution for each exposure period i.e. 7, 28 & 91
days.
4. Results and Discussion:
4.1 Sulfate Resistance of concrete mix with BFS and control concrete:
4.1.1 Visual Appearance:[5]
The visual appearance of test specimens after exposure is shown in figure 4.1. It can be seen from the visual
appearance of the test specimens after soaking in sulfate solution for the exposure periods, there is no significant
change in the appearance of the specimens compared to the condition before they are exposed. However, white
patches are observed on the specimens both for sodium as well as magnesium sulfate solution. There is no sign
of surface erosion, cracking or spilling on the specimens
Figure 4.1: Effect of Sulfate
% Mass Gain
4.1.2 Change in Mass for concrete mix with BFS and control concrete:[5]
Figure 4.2 and 4.3 presents the test results on the change in mass of specimens soaked in sodium and
magnesium sulfate solution for 7, 28 and 91 days period as a percentage of the mass before exposure. There is
no reduction in the mass of the specimens, as confirmed by the visual appearance of the specimens. There is a
slight increase in the mass of specimens of both types of solutions due to the absorption of the exposed liquid.
The increase in mass of specimens in sodium sulfate solution is 0.51%, 0.66% and 0.82% for concrete mix with
BFS, control concrete has 0.39%,0.50% and 0.59% increase and in magnesium sulfate solution is 0.31%, 0.40%
and 0.55% for concrete mix with BFS, control concrete has 0.19%,0.27% and 0.35% increase after exposure of
7, 28 and 91 days respectively.
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0.82
0.66
0.59
7 days
0.51
0.50
28 days
0.39
91 days
7 days
28 days
91 days
concrete with sand
concrete with slag
7, 28, 91 days of exposure period
Figure 4.2: % Change in mass after 5% sodium sulfate exposure
0.55
0.60
% Mass Gain
0.50
0.40
0.35
0.40
0.27
0.30
7 days
0.31
28 days
91 days
0.19
0.20
7 days
0.10
28 days
0.00
91 days
concrete with sand
concrete with slag
7, 28, 91 days of exposure period
Figure 4.3: % Change in mass after 5% magnesium sulfate exposure
4.1.3 Change in Compressive and flexural strength after sulfate exposure: [5,16]
The percentage reduction in compressive and flexural strength for concrete mix with BFS as well as control
concrete in sodium sulfate solution is shown in figure 4.4 and 4.6. Similarly percentage reduction in
compressive and flexural strength for concrete mix with BFS as well as control concrete in magnesium sulfate
solution is shown in figure 4.5 and 4.7.
% Reduction in compressive
strength
1.40
1.20
1.00
1.06
1.16
0.96
1.03
0.80
0.68
0.80
7 days
28 days
0.60
91 days
0.40
7 days
0.20
28 days
0.00
concrete with sand
concrete with slag
7, 28, 91 days of exposure period
Figure 4.4: % Reduction in compressive strength in 5% sodium sulfate solution
91 days
% Reduction in compressive
strength
1.40
1.25
1.12
1.20
1.00
1.05
0.91
1.12
7 days
0.86
0.80
28 days
0.60
91 days
0.40
7 days
0.20
28 days
0.00
concrete with sand
concrete with slag
91 days
7, 28, 91 days of exposure period
Figure 4.5: % Reduction in compressive strength in 5% magnesium sulfate solution
% Reduction in flexural strength
1.40
1.25
1.20
1.00
1.00
0.80
0.86
0.78
0.91
0.71
7 days
28 days
0.60
91 days
0.40
7 days
0.20
28 days
0.00
91 days
concrete with sand
concrete with slag
7, 28, 91 days of exposure period
Figure 4.6: % Reduction in flexural strength in 5% sodium sulfate solution
1.31
% Reduction in flexural strength
1.40
1.20
1.24
1.21
1.06
1.01
0.94
1.00
7 days
0.80
28 days
0.60
91 days
0.40
7 days
0.20
28 days
0.00
91 days
concrete with sand
concrete with slag
7, 28, 91 days of exposure period
Figure 4.7: % Reduction in flexural strength in 5% magnesium sulfate solution
4.2 Acid Resistance of concrete mix with BFS and control concrete:
Acid resistance for concrete with sand and BFS has been evaluated and comparison of parameter like % change
in mass and % reduction in compressive as well as flexural strength due to acid attack are studied. Visual
appearance of specimens is also studied to understand the effect of acid attack.
4.2.1 Visual Appearance: [5]
Visual appearance of specimen for concrete mix with BFS soaked in sulfuric acid solution is shown in figure
4.8. It can be seen that the specimen exposed to sulfuric acid undergoes erosion of the concrete surface and
control concrete shows higher erosion compared to concrete mix with BFS. After 4-5 days, coarse aggregates of
concrete are exposed as the surface undergoes erosion. Also initial surface erosion is significantly higher for
control concrete.
Figure 4.8: Effect of Acid
4.2.2 Change in Mass of concrete mix with BFS and control concrete: [5]
Figure 4.9 to 4.11 shows graphical representation of mass loss in concrete mix with BFS and control concrete
for various percentage of sulfuric acid like 0.5%, 1%, 2% for 7, 28, 91 days of exposure period. Control
concrete specimens have significant mass loss compared to concrete with BFS having same exposure. Concrete
with BFS shows good resistance to acid and very less mass loss has been observed throughout the test. Mass
loss due to acid exposure increases with the increase in percentage of concentration of acid for both type of
concrete.
% Change in mass
3.00
2.56
2.50
2.00
2.16
1.90
1.68
28 days
1.38
1.50
7 days
91 days
0.98
1.00
7 days
0.50
28 days
0.00
concrete with sand
concrete with slag
91 days
7, 28, 91 days of exposure period
Fig. 4.9 % Change in mass after 0.5% sulfuric acid exposure
% Change in mass
3.50
3.02
2.74
3.00
2.50
2.38
2.02
1.86
2.00
28 days
1.24
1.50
7 days
91 days
1.00
7 days
0.50
28 days
0.00
concrete with sand
concrete with slag
91 days
7, 28, 91 days of exposure period
% Change in mass
Fig. 4.10 % Change in mass after 1% sulfuric acid exposure
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
4.13
3.08
2.91
2.35
2.29
1.75
7 days
28 days
91 days
7 days
28 days
concrete with sand
concrete with slag
7, 28, 91 days of exposure period
Fig. 4.11 % Change in mass after 2% sulfuric acid exposure
91 days
4.2.3 Change in Compressive and flexural Strength after acid exposure: [5,16]
The percentage reduction in compressive strength for concrete mix with BFS as well as control concrete for
various percentage of acid concentration are shown in figure 4.12 to 4.14. Similarly percentage reduction in
flexural strength for concrete mix with BFS as well as control concrete for various percentage of acid
concentration are shown in figure 4.15 to 4.17. % reductions in compression and flexural strength for exposure
period of 91 days are much higher as compare with 7 and 28 days of exposure period for both type of concrete.
Concrete with BFS provides more protection against acid as compared to control concrete.
3.16
% Reduction in compressive
strength
3.50
2.91
3.00
7 days
2.50
28 days
2.00
1.50
1.04
1.31
1.01
1.25
91 days
1.00
7 days
0.50
28 days
0.00
concrete with sand
concrete with slag
91 days
7, 28, 91 days of exposure period
% Reduction in compressive
strength
Fig. 4.12 % Reduction in compressive strength in 0.5% sulfuric acid solution
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
3.83
3.63
7 days
28 days
1.94
1.79
1.38
91 days
1.30
7 days
28 days
91 days
concrete with sand
concrete with slag
7, 28, 91 days of exposure period
Fig. 4.13 % Reduction in compressive strength in 1% sulfuric acid solution
4.68
% Reduction in compressive
strength
5.00
4.42
4.00
3.00
7 days
2.77
2.57
2.17
28 days
2.06
91 days
2.00
7 days
1.00
28 days
0.00
concrete with sand
concrete with slag
91 days
7, 28, 91 days of exposure period
Fig. 4.14 % Reduction in compressive strength in 2% sulfuric acid solution
% Reduction in flexural strength
3.50
3.02
3.00
2.41
2.50
2.00
1.50
1.24
28 days
1.47
0.94
1.00
7 days
1.20
91 days
7 days
0.50
28 days
0.00
concrete with sand
concrete with slag
7, 28, 91 days of exposure period
Fig. 4.15 % Reduction in flexural strength in 0.5% sulfuric acid solution
91 days
7, 28, 91 days of exposure period
% Reduction in flexural strength
4.00
3.42
3.50
3.13
3.00
7 days
2.50
2.00
2.01
28 days
1.93
1.47
91 days
1.33
1.50
1.00
7 days
0.50
28 days
0.00
91 days
concrete with sand
concrete with slag
% Reduction in flexural strength
Fig. 4.16 % Reduction in flexural strength in 1% sulfuric acid solution
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
4.21
4.11
3.01
2.73
2.33
1.96
7 days
28 days
91 days
7 days
28 days
91 days
concrete with sand
concrete with slag
7, 28, 91 days of exposure period
Fig. 4.17 % Reduction in flexural strength in 2% sulfuric acid solution
5. Conclusion:
Based on the evaluation of results worked out from experimentation, it is found that concrete produced with
BFS have superior protection against sulfates and acid exposure compared to control concrete. Effect due to
magnesium sulfate is more severe as compare to the sodium sulfate on the concrete. Specimen exposed to the
sulfates shown slight increase in mass rather than loss in mass due to less deteriorative effect of sulfates. At the
same time deteriorative effect in control concrete is more than the concrete with BFS. Effect due to sulfuric acid
is become more severe as the concentration of sulfuric acid solution increases from 0.5% to 2% on the concrete.
Visual appearance of specimens after sulfate and acid exposure gives the useful information of behavior and
pattern of erosion, deterioration in the concrete. Flexural strength of concrete exposed to sulfate and acid
indicate good resistance, promises the use this concrete in road construction especially in jetty, harbor and other
costal line construction. Concrete mix with BFS has shown excellent sulfate and acid resistance. This confirms
that it is more suitable at sulfate prone areas and at the same time indicative of good durable concrete in
hazardous environmental condition.
Acknowledgements:
The support and permission received from Civil Department of Atmiya Institute of Technology and Science,
Rajkot is highly appreciated and acknowledged. We wish to thanks the support and advice received from staff
members of Chemistry Department and the laboratory staff.
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