Introduction: Objective, scope Deterioration of Concrete Structures: Penetrability of concrete permeability, sorptivity, diffusion. Physical processes- abrasion, erosion. Chemical- carbonation, chloride and sulfate attack. Alkali –

1. DEPARTMENT OF
CIVIL ENGINEERING
5CE5-14: REPAIR AND
REHABILITATION OF STRUCTURES
Introduction: Objective, scope
Deterioration of Concrete Structures
Er. Ramprasad Kumawat
M.Tech

2. OBJECTIVE
• To get the knowledge on quality of concrete,
durability aspects, causes of deterioration,
assessment of distressed structures, repairing
of structures and demolition procedures.

3. scop
• Repairs and rehabilitation engineering being a
specialized field calls for skills and abilities far
beyond the construction engineering and has to
be a balance amid advanced technology and
trends, management, feasibility and economy

4. Deterioration of Concrete Structures
• Penetrability of concrete permeability,
sorptivity, diffusion.
• Physical processes- abrasion, erosion.
• Chemical- carbonation, chloride and sulfate
attack.
• Alkali – Aggregate Reaction.
• Corrosion- mechanism.

5. Deterioration of Concrete Structures
• Cement concrete is the most extensively used
material for construction of different types of
structures/components such as buildings, bridges
and shell roofs and also for precast products such
as pipes, poles, sleepers etc…
• Too much emphasis is placed on concrete
compressive strength rather than on
environmental factors, which are known to affect
concrete durability.
• This is one of the main reasons for serious
deterioration of concrete structures.

6. Penetrability of concrete permeability
• Permeability of concrete is defined as the
property that controls the rate of flow of fluids
into a porous solid. It largely depends on the size
of pores, connectivity of pores, and how tortuous
the path is for the permeating fluid.
• The pores relevant to permeability are those with
a minimum diameter of 120 or 160mm, and they
have to be connected.
• Isolated pores, pores filled with water, and pores
with a narrow entrance and irrelevant to
permeability.

7. Factors Influencing Concrete
Permeability
• There are three major factors that influence the
permeability of concrete :
• 1. Water to Cement ratio
• 2. Compaction of Concrete
• 3. Curing of Concrete
• 4. Other Factors

8. 1. Water to Cement ratio
• Water to cement ratio influences concrete
permeability to a great extent. The higher the
w/c ratio the greater the concrete permeability.
In this case, not only does sizable free water
remain in concrete after completion of cement
hydration but also particles of cement and
aggregate would not be as compact as in the
case of low water to cement ratio.

9. • Fig.1 explains the relationship between water
to cement ratio and concrete permeability.
Typically, at a water cement ratio of around
0.4, permeability is practically nil.
• Finally, super plasticizer with mixture allows
the use of low water to cement ratio, so
concrete with low permeability can be
produced with the use of super plasticizer.

10. Fig. 1: Relationship Between Permeability and Water to Cement Ratio for
Mature Cement Paste

11. 2. Compaction of Concrete
• When concrete is adequately compacted, air-
voids and trapped bleed water in concrete are
eliminated. As a result, pores and more
importantly interconnected pores are avoided
and eventually concrete permeability is
declined.
• Therefore, it is crucial to select and use proper
and suitable compaction equipment during
concrete placement and supervise the work to
achieve the desired compaction.

12. 3. Curing of Concrete
• It is obvious that curing of concrete
substantially influences the permeability of
concrete. Sufficient curing allows proper
cement hydration. Subsequently, pores in
concrete would be filled with hydration
product.

13. Fig. 2: Factors Controlling Permeability

14. 4. Other Factors
• There are other factors that affect concrete
permeability, but are not as influential as those
discussed above. For example, age of concrete,
cement properties, aggregate, use of
admixtures, and loss of mixing water.
Permeability declines as the concrete age
increases because pores would be filled by
hydration product.

17. Chemical- carbonation, chloride and
sulfate attack

30. Physical processes- Abrasion, erosion
• Abrasion is a process of erosion which occurs
when material being transported wears away at
a surface over time.
• It is the process of friction caused by scuffing,
scratching, wearing down, marring, and
rubbing away of materials.
• The intensity of abrasion depends on
the hardness, concentration, velocity and mass
of the moving particles.

31. • Abrasion generally occurs four ways.
1. Glaciation slowly grinds rocks picked up by
ice against rock surfaces.
2. Solid objects transported in river channels
make abrasive surface contact with the bed and
walls.
3. Objects transported in waves breaking on
coastlines cause abrasion.
4. Abrasion can be caused by wind
transporting sand or small stones against
surface rocks.

32. • Thanks!
• Gmail :- ramkumawat001@gmail.com