| Concrete cracking is a common phenomena in concrete structures across the world-wide. Cracks in concrete can be developed from the curing time of concrete to end of it's service life. Usually, when cracks appear in concrete, the structure of a building or bridge takes on an unaesthetic appearance, which attracts the attention of all of us. Some types of cracks in concrete may harm full for the structure or create alarming situation. |
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Types of Concrete Cracking || Cause, Repair Concrete Cracks
Types of Concrete Cracking: Based on Impact
Types of cracks in concrete structure can be classified in two categories based significant impact on the structure: 1. Non-structural cracks and 2. Structural Cracks.
1. Non-Structural Cracks:
Non-structural cracks are those types of cracks that have no effect on the structure i.e. shrinkage cracks, thermal cracks, mapping cracks, crazing, hairline cracks, fine cracks etc. These types of cracks can be appear on structure with out copromising structural strength but lead to degradation of concrete.
Causes of Cracks in Concrete:
Shrinkage Cracks in Concrete:
After casting of concrete members we left the concrete memebrs for curing. Volume of concrete will redured during concete curing due to loss of moisture and concrete hydration process. surfacec tension will be created outer site of the concrete layer and cracked the our surfaces. The cracks which are developed on concrete face due to shrinkage of concrete, are called shrinkage crack.
Thermal cracks/ Mapping cracks/ Crazing in Concrete:
These type of cracks are developed due to temperature variation from inner concrete layers to outer faces. Cracks will develop on outer face of concrete member due to un-equal expansion and contruction during variation of temperature.
2. Structural Cracks:
Structural cracks are those types of cracks that have significant impact on the structure like reduce load carrying capacity, break integrity of concrete. Minor cracks, major cracks, shear cracks, flexural cracks, internal micro cracks etc. are the structural cracks.
Shear Cracks:
Every concrete member section have limit of permssible shear stresss. Maximum shear forrce develops near to the support at critical cross section. If the maximum shear stress is cross the limit of parmissible shear stress, cracks will be developed at side face of concrete member. Shear cracks develop in diagonal direction. Shear cracks can be developed due to insufficient cross section, lack of shear stirrups, excessive loads etc.
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| Picture: Shear Cracks in Concrete Structure. |
Flexural Cracks:
Concrete is in brittle nature in tension and strong in compression. Cracks are easily developed in tension zone. Compressive stress developes at top and tensile stress developes at bottom layer due to bending moment. Thats why steel reinforcements provide in tension zone to take bending moment. If maximum beneding moment is exceed to the moment of resistance by steel reinforcements, cracks will be developed at face of the concrete member. Cracks start from the outer tension face to the neutral axis. Flexural cracks develop in vertical direction. Some times flexural cracks can be developed in slightly digonal direction due to combination of bending stress and shear stress.
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| Picture: Flexural Craks in Concrete Strucutre |
Types of Concrete Cracking: Based on Cracks Width
Type of cracks in concrete based on crack width can be classified into following categories:
1. Hairline Cracks:
Hairline cracks are not clearly visible by naked eyes. This type of cracks can be examined by magnifying glass. The width of cracks is less than 0.10 mm.
2. Fine Crack:
Fine cracks are more visible than hairline cracks. This type of cracks can be clearly visible by naked eyes. The width of the fine crack is more than 0.10 mm and less than 0.30 mm. Both hairline cracks and fine cracks are considered non-structural cracks.
3. Minor Crack:
The width of the minor cracks varries from 0.30 mm to 0.50 mm.
4. Major Cracks:
The width of major crack varries from 0.50 mm to 1.00 mm.5. Widen crack:
The width of cracks is greater than 1.00mm. |
| Picture: Widen Cracks at Bottom of Girder in Longitudinal Direction. |
>>As per Indian Road Congress IRC:112-2011, the permisible width of cracks is
| (Condition of Exposure) | (RCC members/ PSC members with un-bonded tendons) | (PSC members with bonded tendons) |
|---|---|---|
Modarate | 0.30 mm. | 0.2mm. |
Severe | 0.30 mm. | 0.2mm. |
Very severe and Extreme | 0.2mm. | 0.2mm. |
Width of hairline cracks are within maximum permissible limit in concrete structure. So, there is no need to carry out any type of crack repair in concrete. But protective paint or epoxy paint should be applied on concrete members to seal crack face and to prevent mosture intering into the inner concrete layer.
Read More:
- Corrosion In Reinforced Concrete || Causes Of Corrosion_Remedial Measures
- Defects In Concrete Bridge Structures || Bridge Defects Type, Causes and Prevention
- Procedures For Maintenance And Rehabilitation Of Bridges
- Bridge Bearing Replacement Procedure
- Failure of Reinforced Earth Wall || Causes of RE wall Failure
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