CHAPTER 1 INTRODUCTIONshodhganga.inflibnet.ac.in/bitstream/10603/33583/6/06_chapter 1.pdf · They...
Transcript of CHAPTER 1 INTRODUCTIONshodhganga.inflibnet.ac.in/bitstream/10603/33583/6/06_chapter 1.pdf · They...
1
CHAPTER 1
INTRODUCTION
1.1 GENERAL
The water requirements are linked with the density of population
and the growth of industrial activity. As the population and the industrial
activity increase, it is susceptible to have more possibilities of water scarcity.
Even though water is surplus on the earth, approximately 97% of the water
contains salt and it is not suitable for domestic (cooking, drinking, etc.),
construction and various industrial purposes. The remaining two percent of
water is in the form of ice and one percent of the total water is only usable
water, of which ground water accounts for 98% and the surface water
accounts for 2%. Therefore such a limited resource is very precious and it
needs to be utilized economically (Irshad Ahmad 2004). According to the
United Nation’s study, the world population and the industrial development
continue to surge and the availability of freshwater is on the decline and in the
next two decades many of the countries in South Asia, Middle East Asia and
Africa will face water crisis (Bosnic et al 2000).
Due to urbanization and industrialization, construction industry is
in the rapid pace of development in India. A large quantity of water is
required for the entire construction activity which includes mixing of concrete
ingredients, curing of concrete, washing of equipments etc. Both in developed
and in developing countries water depletion issues are the major problems and
hence an alternate has to be found out to replace the potable water used in the
2
construction industry with some other re-used industrial effluent. The ground
water level will not be affected if the waste water is used for construction
purpose.
The waste water let out from various industries such as tanneries,
textile processing units, rice mills, dairy farms, paper mills, etc., are
considered for re-using in the construction activity. More number of tanneries
and textile processing units are clustered in South India and a huge amount of
water is let out from the tanneries and textile processing units after processing
the raw materials. From a quantitative analysis, the water that is let out from
the textile and tannery industries after the processes are approximately 80,000
– 1,40,000 litres and 40,000 litres per ton production of processed clothes and
processed tannery products respectively (Garg 1998). All over India there are
approximately 2,000 tanneries and 5000 textile processing units located at
different centres which let out huge amount of water after processing
(Madhuri Raju and Tandon 1999). Even the treated water from tannery and
textile processing units cannot be used in the same industries because the
quality of the end products will be affected. Hence in this present study, the
feasibility of using the tannery and textile processed effluents in the
construction activity is examined distinctly for the safer and useful disposal.
From the literature, it is found that there is considerable amount of
sulphate and chloride content present in the tannery and textile effluent (Brent
Smith 1986). Due to the presence of sulphate, it is expected that there may be
sulphate attack in the form of spalling and cracking which may lead to
disintegration of the concrete structures (Brent Smith 1986, Al-Harthy et al
2005). Due to the presence of chloride content there may be a possibility of
chloride attack which may cause corrosion in the reinforcement bars
embedded in the concrete (Glass and Buenfeld 1998). In addition, due to
lower pH (acidity nature) there may also be corrosion of reinforcement bar
3
embedded in the concrete. So the effect of sulphate and chloride content in the
tannery and textile effluents on the properties of concrete have to be examined
thoroughly. Hence in this present research an attempt has been made to study
the effects of sulphate attack on the concrete, chloride attack on the concrete,
corrosion of steel reinforcement embedded in the concrete etc in detail.
To obtain necessary data, several reinforced concrete wharf
specimens are prepared and laboratory tests have been carried out to
determine the concrete properties. The first chapter gives the details about the
introduction, literature review, objective and scope of the project. The second
chapter gives details about experimental methods followed in the study. The
third chapter gives details about results, discussions and cost benefit ratio of
the study. The fourth chapter gives details about conclusion of the study.
1.2 REVIEW OF LITERATURE
Many investigators have studied and reported on various properties
of the concrete prepared using different type of waters and admixtures. This
chapter reviews the available important studies on the various properties of
the concrete such as compressive strength, tensile strength, flexural strength,
sulphate attack, chemical attack, corrosion of the reinforcement bar embedded
in the concrete, concrete degradation, reliability assessment etc and are
discussed in detail.
Kaushik and Islam (1995) prepared and cured the concrete samples
using sea water. They examined the concrete properties such as setting time,
compressive strength of the concrete, corrosion of reinforcement bar
embedded in the concrete and chloride ion penetration of the concrete over a
period of 18 months. They reported that the compressive strength of the
concrete samples prepared using the sea water was less than that of the
4
concrete samples prepared using the potable water. The setting time was
prolonged for the concrete sample prepared by using the sea water. The
corrosion of reinforcement bar embedded in the concrete and chloride ion
penetration were more in the concrete specimen cast using the sea water.
Kilinckale (1997) conducted the experiment by preparing the
concrete specimens adding silica fume, rice husk ash, blast furnace slag and
fly ash as 20% replacement of portland cement. After 28 days of curing, the
concrete specimens were immersed in 5% magnesium sulphate solution and
in 5% hydrochloric acid solution separately. The effects due to sulphate attack
and chemical attack (hydrochloric acid) were measured based on the
reduction in the compressive strength and the loss of weight of the concrete
after 56 days. He reported that the compressive strength of the concrete
specimen blended with pozzolanic material such as fly ash, silica fume, rice
husk ash and metakaoline etc subjected to sulphate attack and chemical attack
was greater than that of the conventional concrete. The loss of weight of the
concrete specimen was less in the concrete blended with pozzolanic material
than that of the conventional concrete. The increase in the compressive
strength and the decrease in the loss of weight of the concrete specimen are
due to the reduction in porosity and increase in binding capacity of the
concrete.
Khatri et al (1997) ascertained that durability of the concrete
structures mostly depended on the permeability of the concrete and not on the
chemistry of cement. He appraised the sulphate attack of concrete by
exposing the concrete specimen to 5% sodium sulphate (Na2So4) solution and
noted that there was considerable loss of weight and reduction in the
compressive strength of the concrete. By the addition of silica fume with the
concrete specimen, the pores in the concrete specimen were reduced. As a
result the permeability of the concrete was reduced and it leads to the decrease
5
in the loss of weight and increase in the compressive strength of the concrete.
He reported that the resistance to sulphate attack was offered by the concrete
specimen blended with high slag cement and 7% silica fume.
Yilmaz et al (1997) have investigated the influence of the sulphate
ions and the effect of pH on the strength of the concrete and the corrosion of
reinforcement steel embedded in the concrete. The concrete samples were
prepared and cured with water having different sulphate ion concentrations
(standard, 400 ppm and 3500 ppm) and distilled water. Then the concrete
samples were exposed to the natural environments for a period of 90 days.
They reported that the compressive strength of the concrete sample decreased
as the sulphate ion concentration increased. The corrosion of reinforcement
steel embedded in the concrete prepared and cured in higher sulphate ion
concentration solutions was higher than that of the concrete prepared and
cured using distilled water.
Glass and Buenfeld (1998) evaluated the transport of the chloride
ions using diffusion cell and developed an exemplar for concentration profile
and duration of penetration of the chloride ions in the concrete. They reported
that the major factor affecting the service life of concrete structure was the
transport of chloride ions through the concrete which leads to chloride attack
and further leads to corrosion of reinforcement bar embedded in the concrete.
They concluded that the concrete structure with higher penetration of chloride
ions for longer duration was affected more than that of the concrete with
lower penetration of chloride ions for shorter duration.
Luping Tang (1999) determined the chloride ion diffusion through
the concrete by measuring the counter electrical potential, ratio of cation
velocity to anion velocity and friction co-efficient. He observed that the
important factor affecting the life of concrete structure was the transport of
6
chloride particles and other micro particles through the concrete. The
transport of such particles leads to the chloride attack and the corrosion of
reinforcement embedded in the concrete which finally resulted in structural
damage of the structure. He analytically derived the formula for the rate of
diffusion of chloride particles through the concrete specimen.
Young et al (1999) studied the sulphate attack on the high strength
concrete blended with silica fume by immersing the concrete samples in
magnesium sulphate and sodium sulphate solution separately. They observed
that there was reduction in the compressive strength of the concrete due to the
sulphate attack. They noted that the resistance to sulphate attack on the
concrete blended with silica fume was more than that of the conventional
concrete because of the increased water binder ratio and reduction in pore
structure of the concrete. They reported that the compressive strength of the
concrete blended with silica fume was higher than the conventional concrete.
Bing Tian and Cohen (2000) carried out X-Ray analysis and
chemical analysis of the concrete samples to study the effect of the sulphate
attack on the concrete. The sulphate attack was mainly due to the reaction
between the sulphate ions and tricalcium aluminate. This reaction resulted in
the production of ettringite with an increase in volume that resulted in
expansion and subsequent cracking of the concrete. Apart from this, sulphate
ions also reacted with calcium hydroxide and formed gypsum. They
concluded that the ettringite formation during sulphate attack was the main
cause of expansion and deterioration of the concrete.
Gruber et al (2001) examined the properties of the metakaolin
blended concrete such as compressive strength, flexural strength, chloride ion
penetration and expansion due to alkali aggregate reaction of the concrete
over a period of 800 days (more than two years). They observed that the
7
expansion of the concrete due to alkali aggregate reaction, compressive
strength and flexural strength were gradually increasing up to 700 days and
after 700 days it almost became constant which was mainly due to the
decrease in the permeability of the concrete.
Vu et al (2001) have studied the compressive strength and the
sulphate attack of the concrete prepared using various admixtures such as
calcined kaolin, blended kaolin, silica fume etc for a period of 180 days. They
have noticed that by the addition of calcined kaolin, blended kaolin and silica
fume while preparing the concrete, the compressive strength of the concrete
was increased and sulphate attack of the concrete was decreased. They
observed that there was only a marginal change in the compressive strength
and the sulphate attack between 90 days and 180 days of test duration. After
90 days, the variation in the properties of the concrete almost became
marginal.
Ghosh et al (2002 a) reported that the fly ash particles are spherical
in nature and having different size in composition. The size of the fly ash
materials is generally smaller than 200µm and the specific surface area of the
fly ash particles is in the range of 180 m2/kg to 590 m2/kg. The density of the
fly ash is in the range of 1800 kg/m3 to 2900 kg/m3. When fly ash is added
with the concrete there is reduction in the permeability of the concrete and in
turn improving the durability of the concrete structure. This is because of the
fineness and higher density of fly ash particles.
Ghosh et al (2002 b) reported that in China 15% of cement was
replaced with the fly ash for preparing the concrete and in Finland, Ireland,
Japan, Korea, Malaysia, Norway and South Africa 5% of cement was
replaced with the fly ash for preparing the concrete to have better strength and
durability properties of the concrete.
8
Marchand et al (2002) observed that the concrete subjected to
sulphate attack underwent a progressive change in its internal micro structure.
These changes had direct effects on the engineering properties of the concrete
such as swelling, spalling and cracking of the concrete. Due to these changes,
there was a significant reduction in the strength properties of the concrete.
They concluded that by reducing the permeability of the concrete by adding
admixtures, various chemical attacks on the concrete could be reduced and
strength properties of the concrete could be improved.
Li (2003) reviewed and reported that the corrosion of the
reinforcement bar embedded in the concrete is the prevailing factor for the
early and premature deterioration of reinforced concrete structures which
further lead to structural failure characterized by cracking, spalling, and
deflection of concrete.
Woo-Yong Jung et al (2003) examined and observed that the
corrosion of the reinforcement bar embedded in the concrete occurred when
the pH of the concrete was in the range of 11–13. If the concrete had more
chloride ions, it could also induce the corrosion of the reinforcement bar
embedded in the concrete regardless of pH. They reported that the corrosion
due to pH could be minimized by increasing the cover of the concrete.
Adam Neville (2004) determined the sulphate attack on the
concrete by measuring the change in the compressive strength and the flexural
strength of the concrete after exposed to sodium sulphate, calcium sulphate
and magnesium sulphate solutions. He reported that sulphate attack is directly
proportional to the water cement ratio.
Bryant Mather (2004) studied the effect of sulphate attack,
chemical attack, corrosion of reinforcement bar embedded in the concrete and
9
alkali aggregate reaction on the concrete blended with various proportions of
admixtures. The chemical attack and the alkali aggregate reaction on the
concrete were reduced by adding fly ash, silica fume, rice husk ash,
metakaolin, blast furnace slag. Apart from this, addition of the admixture
reduced the corrosion of the reinforcement bar embedded in the concrete. He
suggested that the corrosion of reinforcement bar embedded in the concrete
could be reduced or prevented by coating zinc on the steel reinforcement bar
to be embedded in the concrete before concreting.
Erdogdua et al (2004) studied the chloride attack on the concrete by
immersing the concrete sample in sodium chloride solution and found that
there was a diffusion of chloride particles into the concrete which induced the
corrosion of the reinforcement bar embedded in the concrete. He concluded
that if the permeability of the concrete was reduced, the concrete could be
safeguarded against the chloride attack.
Haque et al (2004) studied the mechanical properties of the
concrete such as compressive strength, tensile strength, modulus of rupture
etc and durability properties of the concrete such as sulphate attack, chloride
attack etc for a period of one year. They observed that when the permeability
of the concrete was reduced by adding admixtures, the compressive strength,
tensile strength, modulus of rupture etc of the concrete were increased and
loss of weight, reduction in mechanical strength due to the sulphate attack and
the chloride attack on the concrete were reduced.
Khatri and Sirivivatnanon (2004) have observed that the variation
in the quality of the concrete was due to different water cement ratio, different
method and level of compaction, different method and extent of curing,
varying thickness of the coating on the concrete (cover depth values) etc.
They concluded that by adopting suitable method for concreting and
10
increasing the cover of the concrete, the service life and the durability of the
concrete structure could be improved.
Nehdi et al (2004) studied the effect of sulphate attack on binary,
ternary, and quaternary blended self consolidating concrete. The fresh
concrete properties such as initial setting time, compaction factor, workability
and compressive strength of the concrete were determined after 1, 7, 28 and
90 days of casting. The sulphate attack on the concrete was determined by
measuring the expansion of the concrete and reduction in compressive
strength of the concrete after immersing the concrete samples in a 5% sodium
sulphate solution for a period of 9 months. They reported that the self
consolidated composite concrete (binary, ternary, and quaternary concrete)
achieved better workability, higher compressive strength, better scaling
resistance and lower sulphate expansion than that of the conventional
concrete.
Olivier Poupard et al (2004) have observed that the corrosion of
steel reinforcement bar embedded in the concrete was the main cause of
degradation of the concrete. Initially, the reinforcement steel embedded in the
concrete was naturally protected from corrosion by the high alkalinity of the
concrete. This alkalinity of the concrete was destructed either by the ingress
of the aggressive ions (chlorides and sulphates present in the water) or by an
acidic environment. They concluded that by giving extra cover to the
reinforcement bar embedded in the concrete, the corrosion of reinforcement
bar embedded in the concrete could be reduced even in the aggressive
environment.
Rui Miguel Ferreira (2004) studied the properties of the concrete
such as alkali aggregate reaction, corrosion of steel reinforcement embedded
in the concrete, permeability and chemical attack. He observed that the
11
properties of the hardened concrete were governed by its micro and macro
structure of the concrete. If the internal structure of the concrete became very
hard, the permeability of the concrete was reduced. In turn it resist the
chemical attack from external sources (e.g., acids and sulphates), within the
concrete (e.g., alkali-aggregate reaction) and other environmental distress
(ingress of moisture through the cracks).
Saricimen et al (2004) studied the effects of using treated effluent
for preparing the concrete as a replacement to potable water. They prepared
the concrete samples using both the potable water and the treated industrial
effluent and allowed the concrete samples for curing in the respective water.
The compressive strength of the concrete was determined after 7, 14, 28 and
90 days of casting. They reported that the compressive strength of the
concrete prepared using treated effluent was higher than that of the concrete
samples prepared using the potable water. The strength of the concrete
samples prepared using treated water was 112% higher than that of the
concrete samples prepared using potable water. The strength of the concrete
samples blended with 8% silica fume using treated effluent was 115% higher
than that of the concrete samples prepared using potable water. There was 8%
to 9% decrease in the setting time of the concrete prepared using treated
effluent than that of the concrete prepared using potable water where as the
setting time of the concrete blended with 8% silica fume prepared using
treated effluent was 10% higher than that of the conventional concrete.
Wombacher et al (2004) observed that the corrosion of
reinforcement bar embedded in the concrete was not initiated under the
alkaline condition. They reported that the concrete cover played a vital role
for preventing the corrosion of steel reinforcement embedded in the concrete
and suggested that by increasing the concrete cover, the corrosion of the steel
reinforcement embedded in the concrete could be delayed.
12
Al-Harthy et al (2005) replaced the potable water with the waste
water obtained from oil production fields and other brackish ground water for
making the concrete samples. They determined the compressive strength of
the concrete samples after 7, 14, 21, 28, 35, 42, 49, 56 and 63 days of casting.
They reported that the compressive strength of the concrete prepared using
waste water was less than that of the concrete prepared using potable water
but the required target mean compressive strength was obtained by the
concrete sample prepared using the water obtained from oil production fields
and other brackish ground water.
Chiara Ferraris et al (2005) observed that the external sulphate
attack on the concrete not only affected the internal structure of the concrete
but also adversely affected the concrete structure by softening and cracking
the outer surface of the concrete. Apart from these observations they also
found out that the sulphate attack was more prevalent in arid regions clustered
with industries.
Eshmaiel Ganjian and Homayoon Sadeghi Pouya (2005) studied
the effect of ingress of the sulphate ions in the concrete specimens prepared
using sea water added with silica fume and granulated blast furnace slag.
They measured the effect of the sulphate attack based on the change in the
compressive strength of the concrete specimen. They reported that the
compressive strength of the silica fume blended concrete was higher than that
of the conventional concrete specimen and the granulated blast furnace slag
blended concrete.
Kapilesh Bhargava et al (2005) reported that the predominant factor
responsible for the deterioration of the concrete was the corrosion of the
reinforcement bar embedded in the concrete. The corrosion of the
reinforcement bar embedded in the concrete damaged the concrete structure
13
by expansion, cracking and spalling of the concrete cover. They also reported
that the structural damage was also due to the loss of bond between the
reinforcement and the concrete and reduction in cross sectional area (due to
loss of weight) of the reinforcement bar embedded in the concrete.
Lee et al (2005 a) have studied and observed the mechanism of
deterioration of the concrete structure subjected to sulphate attack. They
concluded that the mechanism of sulphate attack was due to the chemical
reaction between the hydrates in cement pastes and dissolved compounds
such as sodium sulphate and magnesium sulphate. They observed that the
magnesium sulphate present in the solution induced the deterioration of
concrete which was due to the formation of magnesium gel containing
hydrates (M–S–H gel), as well as gypsum and thaumasite. If sodium sulphate
was present in the solution, the deterioration of the concrete was due to the
reaction of sulphate (So4) ions with the cement paste.
Lee et al (2005 b) have examined the sulphate attack on the
concrete samples blended with 0%, 5%, 10% and 15% metakaolin immersed
in magnesium sulphate solution. They evaluated the sulphate attack on the
concrete based on the visual examination, reduction in the compressive
strength and expansion of the concrete. Based on their experiment results they
reported that the concrete specimens blended with 15% metakaolin showed
lower resistance to sulphate attack due to magnesium sulphate. Where as in
the concrete blended with lower concentration of metakaolin (5%), there were
no remarkable differences in the deterioration of concrete specimens.
Nehdi and Hayek (2005) have studied the effect of the sulphate
attack on the concrete samples made of ordinary portland cement (OPC)
replaced with the pozzolanic materials such as silica fume, fly ash and blast
furnace slag. The concrete samples were immersed in 10% magnesium
14
sulphate (MgSO4) solution and 10% sodium sulphate (Na2SO4) solution. They
monitored the expansion and surface degradation of the concrete samples over
a period of 9 months. They reported that the sulphate attack on the concrete
was characterized by the formation of the white efflorescence on the concrete
surface, scaling of surface of the concrete and crystallization of salts on the
outer surface of the concrete. They concluded that the sulphate attack on the
concrete blended with fly ash and blast furnace slag was less than that of the
non blended conventional concrete.
Poongodi (2005) studied the effects of corrosion inhibitors such as
inorganic anodic inhibitors (calcium nitrite, calcium nitrate), organic cathodic
inhibitors (amino alcohols), amino alcohol based mixed corrosion inhibitor
etc blended with the concrete for reducing the corrosion of the reinforcement
bar embedded in the concrete. She reported that the effect of corrosion of
reinforcement bar embedded in the concrete was considerably reduced by
adding the calcium nitrate as the corrosion inhibitor along with the concrete.
El -Dieb (2006) conducted experiments and measured the
permeability of the concrete for different age durations up to a period of 56
days from the date of preparation of the concrete sample. He reported that the
permeability of the concrete decreased with increase in age duration of the
concrete. Apart from the permeability of the concrete he also observed that
the rate of hydration of cement became slower after 28 days of preparation of
the concrete sample.
Frank Bellmann et al (2006) observed that the concrete was a
material susceptible to the ingress of sulphate ions from the environment and
reported that the deterioration of the concrete due to sulphate attack was
because of the formation of ettringite, thaumasite or gypsum. The
deterioration of the concrete due to sulphate attack was observed based on the
15
loss of weight of the concrete sample and reduction in compressive strength
of the concrete.
Hanifi Binici and Orhan Aksogan (2006) evaluated the sulphate
attack on the concrete blended with high volume ground granulated blast
furnace slag (GGBS) and natural pozzolanic materials (NP) such as fly ash,
silica fume and metakaolin etc. The concrete samples were exposed to 5%
magnesium sulphate solution and 5% sodium sulphate solution. It was
observed that the effect due to sulphate attack on the concrete blended with
ground granulated blast furnace slag (GGBS) and natural pozzolanic materials
(NP) is less than that of the conventional concrete. They reported that
reduction in the compressive strength of the concrete exposed to sodium
sulphate was lower than that of the concrete exposed to magnesium sulphate
solution.
Hossain and Lachemi (2006) studied the deterioration of the
concrete structures due to the presence of sulphate contents in soil,
groundwater and marine environments. They conducted the experiments by
replacing cement with volcanic ash and volcanic pumice for preparing the
concrete. After 28 days of curing, the concrete samples were immersed in
magnesium sulphate solution and sodium sulphate solution separately for a
period of 48 months. They conducted the experiments such as compressive
strength, X-ray diffraction, differential scanning calorimetry, mercury
intrusion porosimetry and rapid chloride permeability to determine phase
composition, pozzolanic activity, porosity and chloride ion resistance. The
deterioration of concrete due to sulphate attack and corrosion of reinforcing
steel embedded in the concrete were evaluated based on the loss of weight of
the concrete and reinforcement steel embedded in the concrete. They reported
that the performance of the blended concrete was better than that of the
conventional concrete.
16
Ismail Yurtdas et al (2006) observed in his experimental study that
the drying process of the concrete brought about desiccation shrinkage which
was due to the increase in suction of moisture, reduction in permeability and
variations in pressure (due to self weight and live load on the concrete
structure). They reported that the mechanical properties of the concrete such
as compressive strength and flexural strength almost became constant after
one year.
Jieying Zhang and Zoubir Lounis (2006) have observed and
reported that the corrosion of the reinforcement steel embedded in the
concrete lead to fracture of concrete by means of cracking, delamination,
spalling of the concrete cover. Apart from this reduction in cross sectional
area of the reinforcement bar embedded in the concrete, loss of bond between
the concrete and the reinforcement steel embedded in the concrete, reduction
in strength of the concrete and decrease in ductility of the concrete were also
observed.
Nabil and Al-Akhras (2006) investigated the effect of the concrete
blended with the metakaolin (5%, 10%, and 15% MK) on the sulphate attack
of the concrete. After 28 days of curing, the concrete specimens were
immersed in 5% sodium sulphate solution for a period of 18 months. The
sulphate attack was appraised based on the expansion of the concrete
specimens and reduction in compressive strength of the concrete specimens.
They reported that the concrete specimens blended with 10%, and 15%
metakaolin had higher sulphate resistance than that of the conventional
concrete specimens.
Rongzhen Dong et al (2006) noted that several cracks on the
surface of the concrete foundations that supported the steel tower of the
Luohe Huaiyang high voltage electricity transmission line which was 20 years
17
old situated in North China. To analyze the deterioration mechanism that led
to cracking, field investigations were carried out and several tests were
conducted on the soil and the concrete by electric probe analysis and chemical
analysis. They found that the concentration of sulphates was high in the
surrounding soil and the coarse aggregates present inside the concrete. They
observed that the sulphate present in the outer surface of the concrete was
higher than that of the inner layer of the concrete. They reported that the
sulphate ions penetrated into the concrete and reacted with the cement to form
ettringite, which lead to the cracking of the concrete.
Sideris et al (2006) investigated the sulphate resistance of the fly
ash blended concrete by immersing in a 5% sodium sulphate (Na2SO4)
solution for a period of 24 months. They reported that by the addition of
pozzolanic admixtures (fly ash) while preparing the concrete the sulphate
resistance of the concrete was improved.
Vijayarangan (2006) examined the effect of sulphate attack on the
concrete and measured it based on the change in mass, loss of weight, and
reduction in compressive strength of the concrete. He reported that the
deterioration of portland cement concrete due to sulphate attack was because
of the formation of expansive gypsum and ettringite which caused expansion,
cracking, and spalling of the concrete.
Zhou et al (2006) studied the effect of sulphate attack and acid
attack on the concrete. They prepared the concrete samples with three
different types of cement and immersed in acid solution and sulphate solution
separately. Based on their experimental results, they concluded that there was
more loss of weight of the concrete specimens subjected to acid attack than
that of the sulphate attack. They observed that there was a formation of
18
thaumasite due to sulphate attack where as there was no such formation was
found in the concrete samples immersed in acid solution.
Byung Hwan Oh and Seung Yup Jang (2007) studied and reported
that the presence of chloride ion in the concrete induced corrosion of
reinforcement bar embedded in the concrete which was one of the major
causes lead to deterioration of the concrete structures. They suggested that the
resistance and prevention of the chloride ion penetration in the concrete could
be achieved by adding the admixtures and increasing the cover thickness of
the concrete.
Dehwah (2007) studied and observed that when the concrete was
exposed to the magnesium sulphate and sodium sulphate, they chemically
reacted with calcium hydroxide present in the concrete and formed gypsum
and corresponding hydroxides such as magnesium hydroxide and sodium
hydroxide. Further the effect of the sulphate attack on the concrete due to
magnesium sulphate was higher than that of the sodium sulphate.
Gopalan (2007) studied the effect of sulphate attack, chloride
attack, acid attack and alkali aggregate reaction on the concrete blended with
the fly ash (pozzolanic material). He observed the effects due to sulphate
attack, chloride attack, acid attack and alkali aggregate reaction on the
concrete based on the loss of weight, reduction in compressive strength and
expansion of the concrete. He reported that more resistance was offered by
the concrete blended with fly ash against sulphate attack, chloride attack, acid
attack and alkali aggregate reaction on the concrete. He concluded that by the
addition of fly ash with the concrete the workability was increased, the
permeability was reduced and the bond strength of the concrete was
improved.
19
Jin Zuquan et al (2007) investigated the effect on the concrete
samples immersed in sodium sulphate and sodium chloride salt solution. The
concrete samples were plain cement concrete (conventional concrete) and the
concrete blended with fly ash in various proportions. The concrete samples
were immersed in three types of solutions (3.5% sodium chloride solution,
5% sodium sulphate solution, mixture of 3.5% sodium chloride and 5%
sodium sulphate solution). They measured the effects on the concrete based on
loss of weight and compressive strength of the concrete. They reported that
there was more loss of weight and decrease in compressive strength of the
concrete immersed in the mixture of 3.5% sodium chloride and 5% sodium
sulphate solution than immersed in sodium chloride solution and sodium
sulphate solution separately. The concrete blended with fly ash had
significantly improved resistance to chloride and sulphate ion ingress into the
concrete. The loss of weight and reduction in compressive strength of the
concrete blended with fly ash were less than that of the conventional concrete.
Krishnaswami et al (2007) studied the compressive strength and
flexural strength of the concrete made of cement replaced with 25% of fly ash
and 50% of fly ash. They reported that the compressive strength and the
flexural strength of the concrete blended with 25% of fly ash was more than
that of the concrete blended with 50% of fly ash and the conventional
concrete. The compressive strength and the flexural strength of the concrete
got reduced when the cement was superseded with 50% of fly ash and more
than 50% of fly ash.
Mohd Firdows et al (2007) observed that most of the concrete
structures got deteriorated mainly because of the corrosion of reinforcement
bar embedded in the concrete. The corrosion of reinforcement bar embedded
in the concrete was accelerated either by chloride attack or by carbonation of
the concrete or by combination of chloride attack and carbonation on the
20
concrete. They suggested that chloride attack and carbonation on the concrete
could be counteracted by adding pozzolanic materials such as fly ash, silica
fume, rice husk ash etc.
Salah and Al-Dulaijan (2007) evaluated the performance of plain
cement concrete and blended concrete exposed to magnesium sulphate
solutions, with varying sulphate concentrations, for a period of 24 months.
They prepared the concrete samples using plain cement, cement replaced with
silica fume and cement replaced with fly ash. The concrete samples were
exposed to magnesium sulphate solutions with five different sulphate
concentration of 1%, 1.5%, 2.0%, 2.5%, and 4.0% separately. The sulphate
resistance of the concrete was evaluated based on visual examination and the
reduction in compressive strength of the concrete. They reported that the
maximum deterioration due to sulphate attack was noted in conventional
concrete than that of the concrete blended with silica fume and fly ash. They
concluded that the addition of fly ash with the concrete enhanced the
resistance more to sulphate attack in sulphate rich environments than the
concrete blended with silica fume.
Tamizheselvi and Samuel Knight (2007) reported that the ingress of
chloride ions into the concrete induced the corrosion of the reinforcement bar
embedded in the concrete. The corrosion of the reinforcement bar embedded
in the concrete resulted in staining, rusting and spalling of the concrete due to
the increase in volume of the reinforcement bar because of conversion of iron
into iron oxide.
Tamer El Maaddawy and Khaled Soudki (2007) reported that the
mechanism of corrosion of reinforcement bar embedded in the concrete was
electrochemical in nature. The corrosion of reinforcement bar embedded in
the concrete occurred only when the alkaline environment of the concrete
21
changed to acidic environment. In the acidic environment, iron oxides were
formed at the surface of the reinforced steel embedded in the concrete which
further lead to cracking and spalling of the concrete.
Aggoun et al (2008) studied the effect on the properties such as
setting time and compressive strength of the concrete blended with various
admixtures such as calcium nitrate, tri-ethanolamine and tri-
isopropanolamine. They reported that the concrete specimen blended with
calcium nitrate had an early setting time and a long term development of
mechanical strength properties. The compressive strength of the concrete
blended with calcium nitrate had increased with respect to increase in
duration of the age of the concrete.
Chatveera and Lertwattanaruk (2008) investigated the sulphate
attack on the concrete samples blended with black rice husk ashes (in various
proportions of 5%, 7% and 10%). The concrete samples were exposed to 5%
sodium sulphate solution and magnesium sulphate solution separately. The
sulphate attack on the concrete samples was determined based on the loss of
weight of the concrete, expansion of the concrete and reduction in
compressive strength of the concrete. There was higher loss of weight and
reduction in compressive strength of the concrete blended with 10% of black
rice husk ashes. The expansion and loss of weight of the concrete samples
exposed to sodium sulphate solution was higher than that of the concrete
samples exposed to magnesium sulphate solution.
Dinakar et al (2008) evaluated the properties such as permeability,
water absorption, acid attack and chloride penetration of the concrete
specimens blended with different proportions of fly ash with cement. The
water absorption of the concrete samples was evaluated based on the change
in weight of the concrete sample immersed in water. The concrete properties
22
such as acid attack and chloride penetration were measured based on the loss
of weight and reduction in compressive strength of the concrete. They
reported that the concrete samples blended with high volume fly ash (more
than 40 %) leads to more loss of weight and reduction in compressive strength
of the concrete than that of the conventional concrete when subjected due to
acid attack and chloride attack. The water absorption and permeability of the
concrete sample blended with high volume fly ash were lower than that of the
conventional concrete.
Guerrero et al (2008) studied the flexural strength of the concrete
specimens blended with fly ash. The concrete specimens were immersed in
simulated radioactive liquid waste which was rich in sulphate and sodium
chloride salts for a period of 180 days. They reported that the flexural strength
of the concrete specimen blended with fly ash was higher than that of the
conventional concrete specimen. The concrete specimen blended with fly ash
was stable against erosion when immersed in simulated chloride radioactive
liquid waste. They concluded that the enhancement of properties of the
concrete was due to the formation of non-expansive Friedel's salt inside the
concrete pores.
Nader Ghafoori et al (2008) studied the sulphate attack on the
concrete blended with fly ash by immersing the concrete samples in 5%
sodium sulphate solution. They evaluated the sulphate attack of the concrete
based on the change in length, loss of weight and compressive strength of the
concrete over a period of 270 days. They reported that the change in length,
loss of weight and compressive strength of the concrete samples blended with
fly ash was lower than that of the conventional concrete.
Rajamane et al (2008) determined the load carrying capacity of the
concrete beams blended with the pozzolanic material (fly ash). They reported
23
that the load carrying capacity of the concrete beams blended with fly ash was
more than that of the conventional concrete beams.
Malathy and Subramanian (2008) studied alkali aggregate reaction
of the concrete using cement mortar bars blended with 5%, 10% and 15% of
fly ash. They reported that the cement mortar bars blended with 5% fly ash
(mineral admixture) was sufficient to reduce the expansion of the cement
mortar bar by more than 75%. They concluded that about 80 - 90% of the
expansion of the cement mortar bars due to alkali aggregate reaction could be
controlled by adding the mineral admixtures as a part of replacement with the
cement while preparing the concrete.
Ramesh (2008) used torrent permeability tester for measuring the permeability of the concrete. He determined the permeability of slabs, walls and other prepared test specimens using the torrent permeability tester. Based on the experimental results, he concluded that the penetration of chloride particles, penetration of sulphate particles and corrosion of steel reinforcement embedded in the concrete mainly depends on the permeability of the concrete. It is evident from the literature that the tannery and textile effluents contain more amount of sulphate and chloride content (Brent Smith 1986). When the concrete is prepared using the tannery and textile effluents, sulphate ions and chloride ions may react inside the concrete causing cracking, spalling, and disintegration of the concrete. The chloride ions react with reinforcement bar embedded in the concrete and leads to the corrosion of the reinforcement bar embedded in the concrete. The corrosion of the reinforcement bar embedded in the concrete leads to cracking and spalling of the concrete, excessive deflection, structural failure and finally structural collapse.
24
Omar et al (2003) used brackish water for preparing the concrete
and used the calcium nitrate as the corrosion inhibitor in their work and found
it to be successful in preventing and reducing the corrosion of reinforcement
bar embedded in the concrete. Saricimen et al (2004) used the treated effluent
for preparing the concrete along with silica fume as admixture and noted that
the adverse effects on the concrete prepared using the industrial effluent was
reduced.
The addition of the pozzalonic materials such as fly ash, diatomaceous earth, metakaolin, silica fume, rice husk ash etc can counteract the ingress of the sulphate ions and chloride ions and in turn it reduces the corrosion of the reinforcement bar embedded in the concrete and increases the strength properties of the concrete (Shetty 2003, Malathy 2004, Sideris et al 2006). Gopalan (2007) used fly ash and found the properties such as corrosion of the reinforcement bar embedded in the concrete was reduced and reported that the properties such as sulphate attack, chloride attack, alkali aggregate reaction were counteracted up to some extent. The admixtures such as calcium nitrite, calcium nitrate, amino-alcohols (ethanolamine and N-dimethy-w-ethanolamine) had been used in the concrete and a good improvement in both corrosion and strength properties of concrete were observed (Poongodi 2005). The admixtures such as fly ash, silica fume and rice husk ash had been used to counteract the chemical attacks like corrosion of the reinforcement bar embedded in the concrete and found that chemical attack on the concrete was reduced and strength properties of the concrete were improved (Hanifi Binici and Orhan Aksogan 2006, Mohd Firdows et al 2007). The commercially available admixtures such as webac- 2061, webac 4170, concare etc can be considered for the counteracting the expected chemical attacks.
From the collected literature various tests were conducted up to 800
days and hence in this study, the parameters such as corrosion studies,
chemical attack, sulphate attack, chloride attack, alkali aggregate reaction,
25
permeability and compressive strength etc are studied and observed for a
period of 2.5 years from the date of casting of concrete specimens. In addition
the strength properties of the concrete such as tensile strength, flexural
strength, failure load of the beam etc which have impact on the concrete are
also to be examined.
1.3 OBJECTIVE AND SCOPE OF THE PROJECT
1. To analyze the characteristics of untreated and treated tannery
effluents, untreated and treated textile effluents.
2. To study the effect on the properties of the concrete such as
compressive strength, tensile strength, flexural strength, bond
strength, sulphate attack, chloride attack, corrosion etc using
tannery and textile effluents.
3. Selection and optimization of suitable admixtures to
counteract the adverse effects of using tannery and textile
effluents on the properties of the concrete.
4. To study the properties of concrete such as sulphate attack,
chloride attack, corrosion, chemical attack, alkali aggregate
reaction, leachability of chloride, leachability of sulphate,
permeability, compressive strength, tensile strength, flexural
strength (PCC), failure load (RCC beams) and bond strength
prepared using potable water, tannery and textile effluents
blended with admixtures for longer duration.