Cracks in concrete

1. Cracks in Concrete
Dr.P.RamaMohanRao
Associate Professor
Centre for Disaster Mitigation and Management
VIT University, Vellore , TamilNadu

2. Introduction
Concreteas material hashighadaptabilitytosatisfymanyaspectsfunctionally
needs
 Economyandmaintenance
 Protectionagainstfireand Environment
 Resistancetocyclicloading
 Explosiveresistanceand better controloverdeflection
RCC structures extensively used for 50 -60 years.
Deterioration of RCC is natural phenomenon
It needs to maintain the functional condition of the structure.

3. The distress in the concrete structures due to
• faulty designs and detailing
• use of inferior and substandard materials
• defects in construction
• extreme loading conditions like severe Earthquakes or
cyclonic storms
• lack of maintenance of the structure etc.,
Concrete structures that are deficient in quality will
reflection its durability
Reinforcement corrosion will be faster and resistance to
accidental fire will be reduced to a very great extent.
Introduction ..,

4. Defects in concrete structures
Cracking of concrete
a)Before concrete hardens
 plastic shrinkage cracks
 plastic settlement cracks
 cracks caused by movement
 of the formwork.
b) After concrete hardens
 Spalling
Honeycombing
Dusting
Crazing
Rain damage
Efflorescence
Blistering
Corrosion of reinforcing bars

5. Visual inspection
Sketches of types of cracks
Sketch of exposed aggregate. Sketch of exposed aggregate.
when concrete has been mixed for too long or
the time of transport has been too long cracking due to sinking of timbering

6. Cracks……
differential settlement of central column
Rusting of reinforcing bars
Rusting of reinforcing bars
insufficient reinforcement

7. Cracks..
High temperatureAbnormal set of concrete
Sinking of concreteEarthquake

8. CAUSES OF DISTRESS OF MALFUNCTIONING
The distress in old concrete structure could be due to one or
more of the following reasons
•Corrosion of the reinforcing bars due to ingress of corrosion
promoting chemicals or due to carbonation of relatively porous
concrete
•Distress caused in the structure due to attack of chemicals in
chemical factories.
•Crack formation due to alkali aggregate reaction, drying shrinkages
or u earthquake damage or uneven settlements.
•Due to impact damage or due to continuous erosion by water,
liquids or solids
•Due to the effect of aerobic and anaerobic bacteria in sewage
disposal or treatment systems.
Fire damage of structures

9. CAUSES OF DISTRESS OF MALFUNCTIONING
•Damage due to the use of poor quality ingredients, poor
workmanship or improper design.
•Change of use of structures, such as
a)Residential to commercial use
b)Increased axial load beyond capacity of columns.
c) Modification of structure for increasing space/accommodation.
•Structures may also require major repair after their normal
constructional lifespan.
•Sometimes buildings are required to be given a new architectural
look to fit in the surrounding

10. Structural malfunction
Causes
•Foundation settlement
•Weak and friable concrete
•Overloading
•Design deficiencies
Effects
•Structurally significant cracks
•Excessive deflection in beams
•Spalling and cracking of cover due to delamination
from the confined core