Concrete durability is affected by many factors including the quality of materials used, water-cement ratio, compaction, and curing. Lack of durability can result in cracking, scaling, spalling, or disintegration of concrete. Environmental factors like abrasion, biological growth, freezing and thawing, or chemical attacks from carbonation, chlorides, acids, or sulfates can also damage concrete over time if not properly addressed. Proper concrete mix design, placement, and curing can improve durability.

1. DURABILITY OF
CONCRETE
Presented by
Mr. T. Vairamuni.,B.E.,
Lecturer/Civil
A.M.K.Tachnological Polytechnic College,
Chennai – 21.

2. WHAT IS DURABILITY OF CONCRETE?
The ability of concrete to resist weathering action,
chemical attack, and abrasion while maintaining its
desired engineering properties.

3. DAMAGE OF CONCRETE DUE TO
LACK OF DURABILITY
• Fine to wide cracks developed in concrete.
• Scaling (localized small patches) of concrete can take place.
• Spalling of concrete can happen. (It is a result of water entering
brick, concrete or natural stone and forcing the surface to peel,
pop out or flake off)
• Disintegration of concrete takes place.
• Deposits of salts can take place, which is called efflorescence of
concrete.
• Complete structure failure can occur.

4. FACTORS AFFECTING DURABILITY
• Type and quality of constituent materials.
• Cement content and water-cement ratio.
• Workmanship to obtain full compaction and efficient curing, and
• Shape and size of member.
• Abrasion
• Biological Factors.
• Temperature Effect
• Environmental Related Physical Problems
• Freezing And Thawing
• Chemical Attacks

5. ABRATION
• Concrete is resistant to the abrasive affects of
ordinary weather
• Abrasion resistance is directly related to the
strength of the concrete

6. ABRATION
• Examples of severe abrasion and erosion are
particles in rapidly moving water, floating ice,
or areas where steel studs are allowed on tires
• For areas with severe abrasion, studies show
that concrete of grade M80 and above work
well.

7. BIOLOGICAL FACTORS
Mosses and lichens
these plants of a higher order, cause
significant damage to concrete. These plants
produce weak acids in the fine hair roots.
The acids that are produced will attack the
cement paste and cause the concrete to disintegrate
and scale

8. BIOLOGICAL FACTORS

9. FIRE

11. FREEZING AND THAWING
• The most potentially destructive weathering
factor is freezing and thawing while the
concrete is wet
• Deterioration is caused by the freezing of
water and subsequent expansion in the paste,
the aggregate particles, or both.

12. FREEZING AND THAWING
• Air-entrained concrete with a low water-
cement ratio and an air content of 5 to 8% will
withstand a great number of cycles of freezing
and thawing without distress.

13. FREEZING AND THAWING

14. CHEMICAL ATTACKS
• Carbonation
• Chloride Attack
• Acid Attack
• Sulphate Attack

15. CARBONATION OF CONCRETE
It is a process by which CO2 from the air
penetrates into concrete and reacts with calcium
hydroxide to form calcium carbonates in
presence of water.
CH + CO2-------------------------- CACO3 + WATER

16. CARBONATION OF CONCRETE

17. CHLORIDE ATTACK
• Chloride attack is particularly important
because it primarily causes corrosion of
reinforcement.
• Statistics have indicated that over 40 per
cent of failure of structures is due to
corrosion of reinforcement.

18. CHLORIDE ATTACK
Prevention measures:
• Use supplementary cementitious materials to reduce
permeability
• Increasing the concrete cover over the steel
• use of corrosion inhibiting admixtures
• epoxy-coated reinforcing steel, surface treatments, concrete
overlays, and cathodic protection

21. ACID ATTACK
Concrete is susceptible to acid attack because of
its alkaline nature. The components of the cement
paste break down during contact with acids.

22. SULPHATE ATTACK
• Sulphates can attack concrete by reacting
with hydrated compounds in the hardened
cement paste
• Result in disintegration of the concret

23. SULPHATE ATTACK
External Sources:
• Soil - gypsum - harmless (0.01-0.05)
• Groundwater-high-manganese and alkali sulphates
• Agricultural soil and water-Ammonium sulphate
• Furnaces - high sulphur fuel
• Furnaces-Chemical industry-sulphuric acid.

24. SULPHATE ATTACK
Internal source:
• Portland cement might be over-sulphated.
• presence of natural gypsum in the aggregate.
• Admixtures also can contain small amounts of
sulphates.

25. SULPHATE ATTACK
Control of sulphate attack:
The quality of concrete, specifically a low permeability, is the
best protection against sulphate attack.
• Adequate concrete thickness
• High cement content
• Low w/c ratio
• Proper compaction and curing

26. SULPHATE ATTACK
• The addition of a pozzolanic admixture such
as flyash
• Use of chloride ions:
the solubility of sulfate ettringite in sodium and calcium
chloride solutions is about 3 times more, than in water
• Use of low C3A content cement

27. ALKALI-SILICA REACTION
“The Cancer of Concrete”

28. Alkali-Silica Reaction
The alkali–silica reaction (ASR) is a
reaction which occurs over time in concrete
between the highly alkaline cement paste and
reactive non-crystalline (amorphous) silica,
which is found in many common aggregates.

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

30. • Concrete quality
• Loss of strength, stiffness, impermeability
• Premature failure of concrete structures
• Economic/Environmental impacts
• ASR decreases concrete service life
• Reconstruction has both environmental and economic
impacts. ex. cement production produces 7% of the
world’s CO2 emissions (a greenhouse gas)
Why is it important to study ASR?

31. When cracks reach the surface of a structure,
“map cracking” results.

32. How to prevent ASR damage
• Avoid high alkali content:
– use low alkali Portland cement: Na20eq < 0.69
– replace cement with low alkali mineral admixtures
• Avoid reactive aggregate (amorphous silica)
• Control access to water: use low water to cement ratio,
monitor curing conditions, use admixtures to minimize
water contact.
• Use lithium additives prior to placement of concrete or as a
treatment in already existing concrete
Alkalis + Reactive Silica + Moisture ASR Gel

33. Alkali-Silica Reaction

34. ASR Damage Examples
Built in 1965, this deteriorated bridge is located 9.7 miles west of Lee
Vining at 9400 feet elevation on the eastern slope of the Sierra Nevada.

35. CRACKS IN CONCRETE
• Plastic Shrinkage Cracks.
• Settlement cracks.
• Bleeding.
• Delayed Curing.
• Constructional effects.
• Early Frost Damage.
• Unsound Materials.
• Shrinkage.
• Drying Shrinkage.
• Thermal Shrinkage.

36. PLASTIC SHRINKAGE CRACKS
• When the loss of water from surface of concrete is
faster than the migration of water from interior to the
surface, the surface dries up.
• It depends upon the rate of evaporation of water from
the surface of concrete

37. PLASTIC SHRINKAGE CRACKS
Prevention measures:
• Moisten the formwork.
• Erect temporary wind breakers to reduce the wind velocity
over concrete.
• Erect temporary roof to protect green concrete from hot sun.
• Reduce the time between placing and finishing. if there is
delay cover the concrete with polythene sheets

38. PLASTIC SETTLEMENT CRACKS
• Plastic concrete when vibrated or otherwise settles. If
the concrete is not free to settle uniformly, then
cracks are formed.
• Non Uniform settlement caused due to large piece of
aggregates or reinforcement.

39. PLASTIC SETTLEMENT CRACKS

40. THERMAL EXPANSION AND SHRINKAGE
• Expansion and contraction of concrete subjected to
ambient increase or decrease in temperature results
concrete cracking.
• Ex: roof slabs, road or airfield pavements , bridge
decks etc.

41. CONCLUSIONS
Factors affecting durability of concrete
• Environmental factors
• Quality of constituent materials
• Quantity of constituent materials
• Quality of workmanship
• Cover to the reinforcement
• Inadequate design
• Improper use of structure