Durability and permeability of concrete are essential for its ability to withstand weathering and chemical attacks over time. The durability of concrete depends on factors like water-cement ratio, cement and aggregate properties, use of admixtures, age of concrete, and exposure conditions. A more permeable concrete is more porous and allows more water penetration. Permeability decreases with lower water-cement ratio, finer cement, use of waterproofing admixtures, and increased age. Cracks in concrete can form due to temperature changes, drying shrinkage, chemical reactions, weathering, and poor construction practices. Reinforcement corrosion occurs via electrochemical processes and can be limited by restricting chlorides, ensuring proper concrete cover, and

1. Durability & Permeability
of concrete

2. Durability
• Durability of concrete is its ability to resist
weathering action, chemical attack, abrasion
or any other process of deterioration .
• When exposed to environment durable
concrete is likely to retain its original form,
quality and serviceability during its lifetime.

3. Factors Affecting Durability
3
DURABILITY
External factors
- Physical ,chemical or mechanical
- Environmental such as extreme temp.
abrasion and electrostatic action
- Attack by natural or industrial liquids
and gases
Internal factors
- Permeability of concrete
- Alkali aggregate reaction
- Volume changes due to the difference in
thermal properties of the aggregate and
cement paste

4. • Requirements for DURABILITY :
1. Exposure conditions
2. Requirements for concrete cover
3. Shape and size of member
4. Type and quality of constituent materials
5. Compaction , finishing and curing of concrete

5. Permeability
• For complete hydration of cement about 38 % of
water by weight of cement is require to fill up the
gel pores . If more water used than concrete
becomes more porous.
• Porous concrete has a higher permeability. Gel
pores are so small so that it do not contribute to the
permeability of cement paste.

7. • Factors affecting Permeability :
 water / cement ratio :
For the pastes hydrated to the same
degree, the permeability is lower with lower W/C
ratio or higher cement content.
 Properties of cement :
For the same W/C ratio coarse cement
tends to produce a paste with higher porosity than
a finer cement.

8.  Use of admixtures :
Use of water proofing admixtures reduce
permeability of lean mixes. In case of porous
concrete surface treatment decreases permeability.
 Age of concrete :
In case of fresh paste the flow of water is
controlled , with progress of hydration
permeability decrease rapidly .

9. Causes of cracks in concrete
1. Temperature and plastic shrinkage
 Plastic shrinkage cracking occurs when subjected
to a very rapid loss of moisture caused by
combination of factors which include air and
concrete temp. relative humidity, wind velocity at
the surface of concrete.
 When moisture evaporates from freshly placed
concrete faster than it is replaced by bleed water
the surface concrete shrinks.

10.  It is usual to see a crack parallel to main steel at
about 4 to 7 m apart. This particularly creates
problems when the slab is for terrace as leakage
starts from these cracks only.

12. 2. Thermal variations :
 All materials expand on heating and contract on
cooling. When there is some restraint to the
movement of a component , internal stress are set
up which results in crack.
 Temperature difference within a concrete
structure may be caused by portions of the
structure losing heat of hydration at different rates
by weather conditions cooling or heating of
component.

13. 3. Drying Shrinkage :
 Drying shrinkage is caused by the loss of moisture
from the cement paste constitute which can shrink
by as much as 1 %.
 If the shrinkage of concrete could take place
without restraint , the concrete would not crack.
When the tensile stress of concrete is exceed , it will
crack.

14. 3. Chemical reaction :
 Deleterious chemical reactions may cause by
cracking . These reactions may be due to materials
to make the concrete or materials that come into
contact with the concrete after it had hardens.
4. Weathering :
 The weathering processes that can cause cracking
include freezing and thawing , wetting and drying
and heating and cooling .

15. 6. Poor construction particles :
 lack of curing
 Inadequate formwork supports
 Inadequate compaction
 Placement of construction joints
7. Construction overloads
 Tension cracking
 Shear cracking

16. Corrosion of reinforcement in concrete
• Corrosion of reinforcement steel is a complex
phenomenon involving chemical , electrochemical
and physical processes.
• When reinforcement steel rusts the volume of iron
oxides formed in 2-4 times greater than the steel
corroded, which results in bursting stresses in the
concrete surrounding the bar.

17. • For corrosion of unprotected steel, necessary
precondition is the formation of electrochemical
cell which comprices two electodes , anode and
cathode.

18. Corrosion

19. • Causes of corrosion and remedial measures :
 Presence of cracks in concrete
 Presence of moisture
 Permeability of concrete
 Carbonation
 Chlorides
 Sulphate attack
 Alkali aggregate reaction
 Inadequate of cover

20. Methods of
Controlling Corrosion
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• Limit the chlorides in water, cement, superplastizers,
etc to acceptable levels
• Provide proper cover as per IS norms
• Cover blocks also need to be of good quality
• Concrete should be properly compacted
• Make dense, impermeable / waterproof concrete
• Have protective coatings wherever suitable
• Ensure proper & timely maintenance of structures

21. Chemical Action
When we are dealing with durability, chemical attack
which results in volume change, cracking and
consequent deterioration of concrete become a major
cause of concern
Types of Chemical attack
• Sulphate attack
• Alkali aggregate reaction
• Chloride ion attack - Corrosion
• Carbonation
• Acid Attack
• Effect on concrete in Seawater
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22. Sulphate attack
• Sulphate attack denotes an increase in the volume of
cement paste in concrete or mortar due to chemical
action between the products of hydration of cement
and solution containing sulphate, and also sodium,
magnesium and Cholorides.
• The expansion reaction results in weakening of
concrete masonry and plaster and formation of cracks
as corrosion as well as corrosion of reinforcement.
• A saturate solution of magnesium sulphate can cause
serious damage to concrete with high w/c ratio.

23. Sulphate attack
Methods of controlling sulphate attack
• Use SRC (sulphate resisting cement)
• Quality concrete - low w/c ratio, well designed and
compacted dense concrete
• Use of air-entrainment
• Use of puzzolana
• High pressure steam curing
• Use of high alumina cement
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24. Alkali - Aggregate Reaction
• Some of the aggregates contain reactive type of
silica which react with alkalies present in cement,
(K2O and Na2O) .
• As a result silicate gel of unlimited swelling type are
formed. This reaction is known as ‘ alkali aggregate
reactions’ .

25. Alkali - Aggregate Reaction
25
• Alkali content (K2O and Na2O) or what is called soda
equivalent.
• This is calculated as the actual Na2O content plus
0.658 times the K2O content of the clinker.
• It should be less than 0.6 percent by mass of
cement.
• Alkalis from all these sources must be included in
finding the total alkalis.
• British standard 5328 : part 1 : 1091 specifies a
maximum of 3.0 kg of alkalis (expressed as soda
equivalent) in 1 m3 of concrete in case of alkali
reactive aggregates are used.

26. • The continuous growth of silica gel exerts osmotic
pressure within the concrete.
• This manifests into cracking and bulging of concrete
Occurrence is due to :
1. High alkali content in
cement (more than 0.6%)
2. Reactive silica in
aggregate
3. Availability of moisture

27. Alkali - Aggregate Reaction
4. Use of pozzolana, slag or
silica fume
5. Control on service
condition, limiting degree
of saturation of concrete
Remedial Measures:
1. Use non-reactive
aggregates from alternate
sources
2. Use low-alkali cement
3. Reduce cement content in
concrete

28. Alkali Silica Reaction (ASR)
Alkalis
+
Reactive
Silica
+
Moisture
ASR
Gel
which
expands
Concrete
expansion
and
cracking
What is ASR?

29. Concrete failure due to ASR

31. Acid attack
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• Concrete is not fully resistant to acids depending
upon the type and concentration of acid.
• Oxalic acid and phosphoric acids are harmless.
• The most vulnerable part of the cement hydrate Is
Ca(OH)2, but C-S-H gel can also be attacked.
• Concrete can be attacked by liquids with pH value
less than 6.5.

32. Acid attack
32
• But the attack is severe only at a pH value below 5.5.
• At a pH value below 4.5, the attack is very severe.
• Cement compounds are eventually broken down and
leached away.
• If acids are able to reach the reinforcing steel
through cracks corrosion can occur leading to further
cracking

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