Most acids will slowly or rapidly disintegrate cement depending on type and concentration, attacking calcium hydroxide most vulnerable but also calcium-silicate-hydrate gel. Siliceous aggregates are more resistant to acid than calcareous aggregates. Chloride enters concrete from various sources and reduces alkalinity, allowing corrosion of reinforcement which statistics show causes over 40% of structural failures.

2. • Most of the acid solutions will slowly or
rapidly disintegrate the cement depending
upon type and concentration.
• Most vulnerable part of cement is Calcium
hydroxide, but Calcium-Silicate-Hydrate gel
can also be attacked.

3. • Siliceous aggregates are more resistant
than calcareous aggregates.
• With sulphuric acid attack, calcium sulphate
formed can proceed to react with calcium
aluminate phase in cement to form calcium
sulphoaluminate, which cause expansion
and disruption concrete.

4. • Concrete can be attacked by acid with pH
<6.5
• As the attack proceeds, all the cement
compounds eventually broken down and
leached away, together with any carbonate
aggregate material.

5. <6.5
4.5-5.5
<4.5
Possibility of acid attack
Severe
Very Severe

7. • Chloride Attack is the reaction of chlorides
with moisture present in concrete which
corrodes the reinforcement.
• Statistics have indicated that over 40% of
failure of structures is due to corrosion of
reinforcement.

8. • Chloride enters the concrete from cement,
water, aggregate and sometimes from
admixtures or by diffusion from
environment.
• It reduces the alkalinity of concrete and the
protective passivity layer can be lost which
results in to corrosion of reinforcement.

9. • Chloride is present in the concrete in two
forms:
1. Bond Chloride
2. Free Chloride
• One third part of total chloride is available as
free the corrosion of reinforcement, other part
is bonded chloride which is incorporated in
the hydration process of cement and being
absorbed on the surface of the gel pores.

10. 1.
2.
3.
Concrete containing metal and steam
cured at elevated temperature and
prestressed concrete
Reinforced concrete or plain concrete
containing embedded metal
Concrete not containing embedded
metal or any material required
protection from chloride
0.4
0.6
3.0

12. 1.Most vulnerable part of cement is
a) Baralyme
b) Calcium Hydroxide
c) Magnesium hydroxide
d) Calcium Oxide
2. Concrete can be possibly attacked by acid
with pH
a) 4.5-5.5
b) <4.5
c) <6.5
d) >6.5

13. 3. Concrete will be attacked very severely by acid
with ___ pH
a) <4.5
b) 4.5-5.5
c) <6.5
d) >6.5
4. Reinforced concrete or plain concrete
containing embedded metal limits chloride
content at ___ Kg/m3
a) 0.4
b) 0.6
c) 1.0
d) 3.0

14. 5. Statistics have indicated that over ___% of
failure of structures is due to corrosion of
reinforcement.
a) 30%
b) 40%
c) 50%
d) 60%
6. Concrete not containing embedded metal
limits chloride content at ___ Kg/m3.
a) 0.4
b) 0.6
c) 1.0
d) 3.0

15. 1. b
2. c
3. a
4. b
5. b
6. d