Effect of marine water on concrete made from opc,ppc

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Ankit patel
Sd. 1110
 Nowadays concrete is increasingly being used in more
hostile environmental condition
 And durability is depend on materials
 In marine structure the concrete has to withstand the
physical, chemical , mechanical action of sea water
and alternate wetting and drying condition with salted water
 Important factor is permeability.
 The deterioration is mainly because of sulphate and
chloride content of sea water
 Dance concrete prevent deterioration and this can be
achieved by replacing cement by mineral admixture.
 Soluble salt – 3.5%by weight
 Sodium and chloride – 11000 &20000 mg/ltr
 Magnesium and sulphate – 1400 to 2700 mg/ltr
 And ph of sea water = 7. 5 to 8.4
 This all are sufficient to deterioration of concrete
 Wetting and drying
 Leaching
 Temp. variation
 Corrosion of steel
 Battering by waves and tides
 Sulphate attack
 Freezing and thawing
 marine atm. Zone
1. corrosion of reinforcement by chloride
2.frost action
 Spash zone
1. corrosion of reinforcement by chloride
2.abrasion due to wave action
3.frost actionf
 Tidal zone
1. corrosion of reinforcement by chloride
2.frost action
3.abrasion due to wave action
4.biological fouling
5.chemical attack
 Submerged zone and sea bad
1.chemical attack
2. biological fouling
•
The corrosion products forming on the steel
have a larger volume than the original steel,
and the expansion of these products exerts a
pressure that increase gradually and becomes
strong enough to crack the concrete cover.
 Changes in relative humidity can
lead to dimensional changes in
material with deformation &
cracking.
 Prolonged high humidity promote
fungal growth and subsequent
decay of organic materials.
 And corrosion rate increases due
to destruction of protective
coatings.
 The corrosion velocity is doubled for
every 10 degree C increase in
temperature.
 sea salt dissolve more easily at the higher
temperature.
 The temperature changes causes alternate
expansion & contraction of material. It
leads to high stresses and gradual
deterioration & rupture.
 When surface temperature fall
sufficiently, moisture may condense on
surface, which become thoroughly
wetted. This may cause corrosion of
material.
 Acid attack
 Portland cement is not very resistance to acid attack.
 In case of sulfuric acid attack it deteriorate concrete and
acid is able to reach to reinforcement.
 The concrete leading to the loss of cement paste and
aggregate from the matrix and cracking , rust staining,
spanning is occurred.
 Alkali silica reaction
 some aggregate containing silica that soluble in highly
alkaline solution.expand , disrupting the concrete.
 Sulfate attack
 there are two chemical reaction involved in sulfate
attack on concrete.
 first the sulfate react with free calcium hydroxide
which is liberated during hydration of cement from
calcium sulfate.
 Next The gypsum combines with hydrate calcium
aluminates to form calcium salfoaluminate.
 Both this reaction result in an increase in volume of
concrete.
 This two chemical reaction in which growth of crystals of
sulfate salts disrupt the concrete.
Cracking- corrosion- cracking cycle
Concrete contains micro cracks
1. Humidity and temperature.
2. Impact of floating objects.
3. Chemical attack, leaching of
cement paste.
4. Freeze attack, overload and other
factor increase permeability of
concrete.
Highly permeable
concrete
Crack growth
Corrosion of
embedded steel
Sea water
and air
 Colour of concrete change from deep grey to lime grey
expose to sea water.
 There is continuous increase in permeability in concrete due
to sea water and its attribute to sulphate attack on concrete.
 Compressive strength over a year is decrease about 15 to
30% with respect to 28 day compressive strength expose to
sea water.
Deteriorations of concrete by chemical
reaction
Exchange reaction
between aggressive fluid
and components of
hardened cement paste
Removal of Ca++
ions as soluble
product
Loss of
alkalinity
Reaction involving
hydrolysis and leaching of
the components of
hardened cement paste
Removal of Ca++
ions as non
expansive soluble
product
Loss of
mass
Substitution
reaction replacing
ca++
Increase in
deterioration
process
Loss of
strength
and rigidity
Reaction involving
formation of
expansive product
Increase in
porosity and
permeability
Cracking ,
spalling
Increase in
internal stress
deformation
Various Codal Provisions
for Marine environment
• As per IS 456:2000
• Min.grade of concrete for RCC is M30.
• Min.cement content is 320 Kg/m3.
• Max.W/C ratio is 0.40 – 0.45.
• Max.chloride content is 0.60 Kg/m3.
• Total sulphate content should not exceed 4% .
• Use Pozzolana cement or slag as far as possible.
• No construction joints within 600mm of the
upper & lower planes of wave action .
• Nominal cover is 45mm – 75 mm.
• As per BS CP 110
• Min.grade of concrete for RCC is M40.
• As per Australian code
• Min.grade of concrete for RCC is M30.
• As per IS 456:2000
• Min.grade of concrete for RCC is M30.
•w/c kept as low as possible.
•Minimum cover should be increased where abrasion may occur.
•Proper curing.
 The deterioration of concrete exposed to
marine environment is a result of
collective action of physical chemical and
biological factors. So stimulating such
environment in the laboratory is very
difficult.
 To facilitate such environment the
following exposure condition was
adopted. The cubes and beams casted for
all the three mixes of opc,ppc and psc
were
 exposed to sea water in following ways:

Specimens fully submerged in sea water
prepared in laboratory to facilitate the
condition of concrete ir submerged zone.

Specimens were half submerged in sea
water in order to facilitate the condition in
tidal zone

Specimens were alternately wetted and
dried and this cycle was completed in 24
hours. This exposure condition facilitate the
location of concrete in splash zone.
coarse aggregates
 Concrete plasticizer
Sea water
 Sea water for experimental programme has been prepared
in the laboratory by dissolving salts in the following
proportion





Nacl – 270 gm/10 liters
Mgcl -32 gm/10 liters
Mgso-22 gm/10 liters
cacl – 13 gm/10 liters
Caso - 6 gm/10 liters
 Preparation of specimen
 Mixing and compacting
mixer machine of capacity 25 kg is used
C.A -20mm, C.A -10mm,F.A,cement,water,plasticizer
 Curing
1.after 24 hours the concrete was kept in normal water
curing tank.
2. after 3,7 and 24 days the specimen were kept in sea
water
 For workability the concrete which was taken out from
mixer is tasted for slump.
 No segregation was observed in any mixes and all mixes
were sticky and highly cohesive.
 For both M35 and M40 concrete.
SLUMP IN MM
PPC
45
PSC
40
OPC
37
 Compressive strength for M35
Exposure
condition
OP-35
compressive
strength in mpa
PP-35 compressive
strength in mpa
PS-35 compressive
strength in mpa
3
7
28
3
7
28
3
Fully submerged
51
53.33
57.7
50
50
48.88 49.77 49
50.5
Half submerged
50
53.53
55
48
50
48
48
48.1
50
Alternate wetting
and drying
45
46.22 48.5
41
47.11
47.11
42
47.2
49
Curing in
days
7
28
 Compressive strength for M40
Exposure
condition
OP-40
compressive
strength in mpa
PP-40 compressive PS-40 compressive
strength in mpa
strength in mpa
3
7
28
3
7
28
3
Fully submerged
58
60
61
54
53
57.7
54.22 50.1
55.7
Half submerged
58
58
57.5
53
52
57.7
52
53.5
Alternate wetting
and drying
51
48.88 50.3
48
48.88 53.53
Curing in
days
7
51
48.88 49
28
53.33
Exposure
condition
Curing in
days
OP-35(mm)
PP-35(mm)
PS-35(mm)
3
7
28
3
7
28
3
7
28
Fully submerged
22
20
20
20
17
18
16
13
10
Half submerged
23
20
20
21
17
19
16
12
11
Alternate wetting
and drying
25
22
20
24
20
22
20
18
15
Exposure
condition
OP-40(mm)
Curing in
days
PP-40 (mm)
PS-40 (mm)
3
7
28
3
7
28
3
7
28
Fully submerged
20
18
15
17
15
15
14
12
12
Half submerged
20
18
15
17
15
15
15
10
15
Alternate wetting
and drying
22
20
19
20
20
20
19
10
18
M35
days 0
15
30
45
60
75
90
PP
0.0
0.0020
0.015
0.046
0.070
0.095
0.17
PS
0.0
0.0003
0.014
0.039
0.055
0.080
0.10
OP
0.0
0.0120
0.049
0.084
0.150
0.300
0.40
M40 days 0
15
30
45
60
75
90
PP
0.0
0.001
0.014
0.038
0.050
0.062
0.078
PS
0.0
0.0
0.006
0.025
0.040
0.055
0.064
OP
0.0
0.0
0.017
0.055
0.065
0.080
0.120
M35
days 0
15
30
45
60
75
90
PP
4.64
4.66
4.68
4.70
4.70
4.74
4.79
PS
4.67
4.65
4.67
4.68
4.70
4.72
4.75
OP
4.85
4.84
4.83
4.83
4.85
4.85
4.85
M40 days 0
15
30
45
60
75
90
PP
4.71
4.73
4.75
4.77
4.8
4.86
4.9
PS
4.77
4.78
4.79
4.81
4.81
4.83
4.85
OP
4.81
4.84
4.87
4.91
4.9
4.91
4.91
 Slag cement has the least expansion, no weight loss and
least weight gain due to sulphate attack . as found in
literature review it is more resistant to sulphate attack than
Ordinary Portland cement and Portland Pozzolana
 After 60 days the weight loss is seen in OPC concrete
while no weight loss is seen in concrete with PPC and
PSC till 90 days. Thus OPC starts showing deterioration
due to sulphate attack after 60 days.
 Pulse velocity in concrete with mineral admixtures is
more at early age but decreases with time and A 90
becomes almost equal to that of OPC concrete. As the
grade of concrete increases the Pulse velocity increase
in all three concretes. Thus, concrete becomes denser
by increasing the grade of concrete.
 Alternate welting and drying (Splash zone) condition is
the most deteriorating exposure condition. In this
condition least damage is found in PSC and most
damage is found in OPC concrete.
 Ordinary Portland cement has more compressive
strength in fully submerged and half submerged
condition and Portland Pozzolana cement and Slag
cement have almost equal compressive strength. The
strength in half submerged condition is little less than
fully submerged condition in all cases.
 PPC and PSC concrete have more effect of curing than
OPC concrete for 3 days. But after 7 days curing the
effect of curing becomes equal on all the three
concretes. The strength and chloride ion penetration
resistance increases as curing period increases from 3
days to 26 days.
Chloride penetration is least in slag cement and most in
Ordinary Portland cement.
In alternate wetting and drying condition slag cement has
the highest strength and Ordinary Portland cement has
the lowest strength.
Thus Slag cement>Portland Pozzolana cement>Ordinary
Portland cement is the series of durability of cements as
far as sea water exposure is concerned.
 Indian concrete journal march 1973.
 Journal of structural engineering vol.32 oct-nov 2005.
 Marine structure by p.kumar mehta.
 Marine structure engineering by Gregory P. Tsinker.
 Concrete technology by m.s.shetty
 Corrosion of steel in concrete by John p. broomfield
 Google
 wikipedia
Thank you
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