What is Crack???

• A crack is a complete or incomplete separation of concrete into two or more parts produced by breaking or fracturing.
• Cracks are one kind of universal problems of concrete construction as it affects the building artistic and it also destroys the wall’s integrity, affects the structure safety and even reduce the durability of structure.
• Break or cause to break without a complete separation of the parts.
• In generally defined as a complete or incomplete separation of either concrete or masonry into two or more parts.
• The success of repair activity depends on the identification of the root cause of the deterioration of the concrete structures.

Affects of Cracks

• Carbon dioxide penetrates into the concrete through the cracks and speed up carbonation around the cracks, thus shortening the structure usage.
• The cracks in the concrete wall could cause the leakage of the building; it reduces the stiffness, durability and seismic performance of buildings.
• Cracks on the wall surface damage to the later rendering, will affect to the appearance.

Types of Cracks

1. Structural Cracks
2. Non-Structural Cracks
3. Based on Width

Structural Cracks

• These cracks occur due to incorrect design, faulty construction or overloading and these may endanger the safety of a building.

Non-Structural Cracks

• They are due to internal forces developed in materials due to moisture variations, temperature variation, crazing, effects of gases, liquids, etc.

Based On Width

• Thin- Less than 1mm in width.
• Medium- 1 to 2mm in width.
• Wide- More than 2mm in width.

Repairing for Cracks in Structures

• Stitching
• Routing and sealing
• Resin injection
• Dry packing
• Polymer impregnation
• Vacuum impregnation
• Autogenously healing
• Flexible sealing
• Drilling and plugging
• Bandaging

Stitching

• In this technique, the crack is bridge with U-shaped metal units called stitching dogs before being repaired with a rigid resin material.
• A non-shrink grout or an epoxy resin based adhesive should be used to anchor the legs of the dogs.
• Stitching is suitable when tensile strength must be re established across major cracks.
• Stitching dogs should be of variable length and orientation.

Routing and Sealing

• This is the simplest and most common method of crack repair.
• It can be executed with relatively unskilled labor and can be used to seal both fine pattern cracks and larger isolated cracks.
• This involves enlarging the crack along its exposed face and sealing it with crack fillers.
• Care should be taken to ensure that the entire crack is routed and sealed.

Resin Injection

• Epoxy resins are usually selected for crack injection because of their high mechanical strength and resistance to most chemical environments encountered by concrete.
• Epoxies are rigid and not suitable for active cracks.
• This method is used to restore structural soundness of members where cracks are dormant or can be prevented from further movement.

Dry Packing

• This method is used for repairing holes having a depth nearly equal to greater than the least surface dimension. i.e. for any holes are narrow slots cut for the repair of cracks.
• This method is not used for shallow depressions.

Causes of Distress of Malfunctioning

• Due to impact of damage or due to continuous erosion by water, liquids or solids.
• Corrosion of the reinforcing bars due to ingress of corrosion promoting
• Damage due to the use of poor quality ingredients, poor workmanship or improper design.
• 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.

Conclusion

• If this cause is properly identified, satisfactory repairs can be done for the improvement of strength and durability, thus extending the life of the structure, is not difficult to achieve.
• Through it is impossible to guarantee against cracking yet attempts can be made to minimize development of crack.
• In case of existing cracks, after detail study and analysis of crack parameters, most appropriate method of correction should be adopted for effective and efficient repair of crack.