CRACKS IN BUILDING

By Civilthings.com

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Contents

1. Introduction
2. Effects of cracks
3. Types of cracks
4. Causes of cracks
5. Techniques to cure cracks
6. Conclusion

INTRODUCTION

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

EFFECTS 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 would 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: These cracks occur due to incorrect design, faulty construction or overloading and these may endanger the safety of a building.
2. Non-Structural Cracks: They are due to internal forces developed in materials due to moisture variations, temperature variation, crazing, effects of gases, liquids etc.
3. Based On Width:

Thin - less than 1mm in width

Medium - 1 to 2mm in width

Wide - more than 2mm in width

CAUSES OF CRACKS

• Elastic Deformation
• Thermal Movement
• Chemical Reaction
• Shrinkage
• Foundation Movement and Settlement of Soil
• Earthquake
• Vegetation
• Poor Construction practices

TECHNIQUES TO CURE CRACKS

Epoxy injection

• Cracks as narrow as 0.002 in. (0.05 mm) can be bonded by the injection of epoxy.
• Epoxy Injection is the method of injecting epoxy into the crack in the concrete to fill up the gaps and stick the concrete together for a long life of concrete.
• The cracks are filled with epoxy as it flows and fills the cracks when applied pressure via ports.

Routing and Sealing

• Routing and sealing of cracks can be used in condition requiring remedial repair and where structural repair is not necessary.
• The method consists of enlarging remedial repair and where structural repair is not necessary.
• The method consists of enlarging the crack along its length on the exposed surface, called chasing or routing, and sealing it with a suitable joint sealant.
• However, routing and sealing can be accomplished on curved surfaces (pipes, piles and pole).

Stitching

• The stitching procedure consists of drilling holes on both sides of the crack, cleaning the holes and anchoring the legs of the staples in the holes, with either a non shrink grout or an epoxy resin-based bonding system.
• Stitching may be used when tensile strength must be reestablished across major cracks.

Drilling and plugging

• Drilling and plugging a crack consists of drilling down the length of the crack and grouting it to form a key.
• This technique is only applicable when cracks run in reasonable straight lines and are accessible at one end.
• This method is most often used to repair vertical cracks in retaining walls.

Gravity Filling

• Low viscosity monomers and resins can be used to seal cracks with surface widths of 0.001 to 0.08 in. (0.03 to 2 mm) by gravity filling.
• High-molecular- weight methacrylate, urethanes, and some low viscosity epoxies have been used successfully.
• The lower the viscosity, the finer the cracks that can be filled.
• Wet surfaces should be permitted to dry several days to obtain the best crack filling.

Conclusion

• Though 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.

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