1) Concrete structures can develop defects due to poor construction practices, poor quality control, and poor structural design and detailing. 2) Common defects include honeycombs caused by improper vibration and workability, cracks due to various stresses, and efflorescence caused by leaching of lime compounds. 3) Defects can be repaired through methods like using non-shrink grouts for honeycombs, grinding surfaces for minor formwork errors, and epoxy bonding, routing, resin injection, or grouting for cracks.

1. Defects in Concrete
Structures

2. What is the Concrete?
CONCRETE
Constituents of Typical
Concrete Sample
• 60-75% of aggregates
• 25 to 40% of cement paste
• About 1 to 2% of voids

3. Concrete Defects
Concrete is known to be a very versatile and reliable material, but some
construction errors and construction negligence can lead to the
development of defects in a concrete structure.
These defects in concrete structures appear because of,
1. due to poor construction practices
2. poor quality control
3. due to poor structural design and detailing

4. Honey-comb
 Honeycombs are hollow spaces and cavities left in concrete mass on the
surface or inside the mass
 Improper vibration and workability of concrete are main causes of
honeycombs in concrete
 Reduces the load-bearing capacity affecting the strength of the structure.
Water and air penetrate inside the structure and Rusting and corrosion of
reinforcement occur

6. Treatment for Honey-Comb
Honey-combs were rectified by using special “Non shrink, cementitious
grout” Called Master Flow 810

7. Features of Construction Grout
• High strength
• Non shrink
• Versatile

8. Defects due to Poor Formwork Installation
 Formwork installation errors include misalignment, movement, loss of
support, failure of forms
 Those mistakes can be repaired with surface grinding to maintain the
verticality of the structure if the error is minor.
 In case of major error, the concrete member shall be repaired by
removing the concrete in the defective area and then reconstructing that
portion of the structural member using suitable methods

10. Efflorescence
 Leaching of lime compounds can lead to the
formation of calcium carbonate or calcium sulphate
on the surface of the concrete

11. Bug Holes
 Bug holes or surface voids are small regular or
irregular cavities formed due to the entrapment of
air bubbles in the surface during placement and
consolidation
 By using Clean and well maintained formworks, can
avoid from this defect

12. Cracks
 All Concrete is open to both in the plastic state and in the hardened
state.
1. properties of concrete and its constituent materials
2. Design practices ,
3. Construction practices and.
4. where in-service conditions,
5. internal or external nature Conditions
Cracks
After
Hardening
Before
Hardening

13.  Structural Cracks are Caused by applied loads
 Flexural Cracks / Tensile Shear Cracks
These cracks can be controlled by providing proper tension reinforcement. Generally flexural stress occurs at
the middle span of the beam where flexural stress is maximum.
 Internal Micro-Cracks (Compressive cracks)
Micro cracking can occur in severe stress zones,
 due to large differential cooling rates
 due to compressive loading.
These are discontinuous microscopic cracks which can become continuous and become a visible sign of
impending structural problems.

14.  Shear Cracks
Cracks in concrete beams due to increase in shear stress appears near the supports
These cracks are inclined at 45 degrees with the horizontal. These cracks in beams can be
avoided by providing additional shear reinforcements near the support where the shear
stress is maximum

15.  Non Structural Cracks include
1. Pre-hardening cracks
2. Cracks in hardened concrete
3. Cracking due to chemical effects
Non-structural cracks are influenced by properties of concrete and its constituent materials, construction
practices. Also ambient temperature , humidity
 Pre-hardening (Plastic) Cracks
These cracks occur within a few hours after the placement and compaction of concrete
I. Plastic Shrinkage Cracks
(Rapid Drying of concrete surface with in 1st Six Hours)
I. Plastic Settlement Cracks
(Caused by concrete settling under its own weight)

16.  Cracks in hardened concrete
1. Craze Cracking
(Characterized by a series of very fine closely spaced map pattern cracks Caused by the
shrinkage of the Cementous material of the surface layer of concrete)
1. Drying Shrinkage Cracks
(Occur when concrete reduces in volume as a result of moisture losses into the atmosphere
in its hardened state)
1. Early Thermal Contraction (Movement) Cracks
(Occur when concrete reduces in volume as a result of moisture losses into the atmosphere
in its hardened state)

17. Crack Repairing
 Bonding with Epoxies
 The Routing operation
 Resin injection
 Stitching
 Grouting
 Blanketing

18. Other Defects
 Concrete Spalling
 Blistering
 Dusting
 Delamination

19. Thank-you for your Attention!