Concrete repair
Cracks and Repairs
R.C.C. Structures
Tool Kit for Engineers
4.10/ P/ 1
Cracks in building
• Structural cracks
– due to incorrect design
– faulty construction
– Overloading
• Non Structural cracks
–
–
–
–
–
–
–
Moisture changes
Thermal movement
Elastic deformation
Creep
Chemical reaction
Foundation movement and settlement of soil
Vegetation
Tool Kit for Engineers
4.10/ P/ 2
Non Structural cracks:
Moisture Changes
Building materials expand on absorbing moisture and shrink on drying. These are generally reversible. Shrinkage in concrete or mortar depends on a number of factors
• Cement concrete: Richer the mix greater is the drying shrinkage.
• Water content: More water in mix induces greater shrinkage
• Aggregates : Large aggregates with good grading has less shrinkage for same workability as less water is used
Tool Kit for Engineers
4.10/ P/ 3
• Curing: If proper curing starts as soon as initial set has taken place and continued for 7 to 10 days shrinkage is comparatively less
• Excessive fines: More fines in aggregate requires more water for same workability and hence more shrinkage. • Temperature: Concrete made in hot weather needs more water for same workability see Fig – 8 and hence results in more shrinkage.
• Temperature: Concrete made in hot weather needs more water for same workability hence results in more shrinkage.
Tool Kit for Engineers
4.10/ P/ 4
Initial Expansion
An example of cracks of wall due to initial expansion of bricks is given in fig
Tool Kit for Engineers
4.10/ P/ 5
Some Measures for controlling shrinkage
• Shrinkage in plastering can be reduced by ensuring proper adhesion. The plastered should not be stronger than the back ground.
• Shrinkage cracks in masonry can be minimized by avoiding use of rich cement mortar and by delaying plastering till masonry has dried after proper curing and has undergone most of its initial shrinkage. Tool
R.C.C. Structures
Tool Kit for Engineers
4.10/ P/ 1
Cracks in building
• Structural cracks
– due to incorrect design
– faulty construction
– Overloading
• Non Structural cracks
–
–
–
–
–
–
–
Moisture changes
Thermal movement
Elastic deformation
Creep
Chemical reaction
Foundation movement and settlement of soil
Vegetation
Tool Kit for Engineers
4.10/ P/ 2
Non Structural cracks:
Moisture Changes
Building materials expand on absorbing moisture and shrink on drying. These are generally reversible. Shrinkage in concrete or mortar depends on a number of factors
• Cement concrete: Richer the mix greater is the drying shrinkage.
• Water content: More water in mix induces greater shrinkage
• Aggregates : Large aggregates with good grading has less shrinkage for same workability as less water is used
Tool Kit for Engineers
4.10/ P/ 3
• Curing: If proper curing starts as soon as initial set has taken place and continued for 7 to 10 days shrinkage is comparatively less
• Excessive fines: More fines in aggregate requires more water for same workability and hence more shrinkage. • Temperature: Concrete made in hot weather needs more water for same workability see Fig – 8 and hence results in more shrinkage.
• Temperature: Concrete made in hot weather needs more water for same workability hence results in more shrinkage.
Tool Kit for Engineers
4.10/ P/ 4
Initial Expansion
An example of cracks of wall due to initial expansion of bricks is given in fig
Tool Kit for Engineers
4.10/ P/ 5
Some Measures for controlling shrinkage
• Shrinkage in plastering can be reduced by ensuring proper adhesion. The plastered should not be stronger than the back ground.
• Shrinkage cracks in masonry can be minimized by avoiding use of rich cement mortar and by delaying plastering till masonry has dried after proper curing and has undergone most of its initial shrinkage. Tool