Causes of Cracks in Concrete and How to Prevent Cracks in Concrete?
What Is Concrete Crack?
Cracking lines on the concrete’s surface may be found along which it splits without breaking apart. These lines are known as concrete cracks.
Causes of Cracks in Concrete
Cracking is one of the most common problems in concrete and should be avoided at all costs. The following are some of the causes of concrete cracking:
2. Shrinkage
One of the most common causes of cracking in hardened concrete is shrinkage. During drying shrinkage, the volume of concrete gradually decreases, and if the component is restrained against free movement, tensile stresses develop, causing cracks.
2. Temperature Changes
Concrete cracks can also appear as a result of weathering processes like freezing and thawing, wetting and drying, as well as heating and cooling. Concrete cracks can develop as a result of water freezing or moisture in the concrete paste.
The movement of water to freezing sites, as well as the hydraulic pressure generated by the growth of ice crystals, cause freezing damage in hardened concrete.
3. Poor Construction Practices
Cracked concrete can sometimes be the result of poor construction practices. The following are some of the poor on-site practices that may cause the concrete to crack:
| POOR PRACTICE | EFFECT OF PRACTICE | FACTOR CAUSING CRACKING |
|---|---|---|
|
Adding water to concrete to improve its workability |
Reduces the strength of the concrete
Improves settlement
|
Drying shrinkage and plastic settlement cracking have increased. |
|
Increasing cement content to compensate for a decrease in strength caused by the addition of water. |
Increases the temperature difference between the structure's interior and exterior sections.
Increases the volume of cement paste |
Dry shrinkage has increased.
Thermal stresses |
|
Inadequate curing |
Lack of hydration in concrete
Reduce your strength. |
Increased shrinkage at a time when the concrete's strength is low |
|
Inadequate consolidation and incorrect placement of construction joints, as well as a lack of support forms |
Improves settlement
Inadequate setting support
Joints open high-stress points |
Concrete cracks due to loads before it has developed enough strength to support itself. |
4. Chemical Reaction
Concrete cracks can be caused by harmful chemical reactions. The chemical reactions could be caused by the materials used to make concrete or by materials that come into contact with the concrete when it has hardened and matured properly.
Cracks in concrete can form over time as a result of slowly developing expansive reactions between active silica aggregates and alkalies derived from the hydration of cement, admixtures, or external sources.
Reaction causes the formation of a swelling gel, which tends to draw water from those other parts of the concrete. This causes local expansion and tensile stresses, and mass eventually results in the structure’s complete deterioration.
5. Errors in Design and Detailing
Excessive cracking may be caused by design and detailing errors, such as insufficient reinforcement, improper foundation design, improper material selection, inadequate precast members and slabs, and inadequate contraction joints, among other things.
6. Construction Overloads and Early Formwork Removal
When the formwork is removed earlier in the construction process, the load that is induced in the structure during that time can also cause cracking.
7. Concrete Corrosion
Steel corrosion produces a large amount of iron oxides and hydroxides, which have a much larger volume than metallic iron. As a result, the volume increases, and cracks appear.
8. Creep and Elastic Deformation
The different parts of the building, including the walls, columns, and beams .When loaded, a slab or other structure deforms elastically. The type of construction materials used, such as bricks, cement concrete blocks, etc., affect how concrete deforms. Cracking develops from this unusual concrete deformation.
How to Prevent Cracks in Concrete?
Concrete can develop cracks in a variety of ways. They are as follows:
The concrete structure must be properly cured. Gunny bags are used to maintain moisture for a longer period of time.
Addition of water in accordance with the concrete's needs and the cement-to-water ratio. Excess water may cause concrete damage.
Using high-quality materials and preparing concrete in accordance with the right mix design
When placing concrete, the appropriate vibration should be used.
If concrete is to be laid from a height, it must be placed properly and at a height of no greater than 1 m.
Concrete can be mixed with shrinkage-reducing admixtures to prevent the development of cracks
Providing adequate control joints in concrete.
Avoid adding calcium chloride admixtures to the concrete mix
Materials Used to Repair Concrete Cracks
Concrete cracks can be repaired using a range of materials. They are as follows:
- Cement mortar
- Cement slurry
- Epoxy resins
- Polymer Modified Cementitious Products (PMCC), such as acrylics, vinyl diene dichloride (PVDD), polyvinyl acetate (PVAC), and styrene-butadiene rubber (SBR).