6 Types of Cracks in Concrete : With Causes & Prevention

6 Types of Cracks in Concrete : With Causes & Prevention

 

In this article, we will discuss 6 types of cracks in concrete with their causes and prevention methods.

Concrete is defined as a composite material that consists of a mixture of fine aggregate, coarse aggregate, and binding material.

The binding material used may be hydraulic cement such as Portland cement or Calcium Aluminate Cement, Lime, Putty, etc.

Concrete is a widely used type of construction material. Despite its immense importance, the absence of proper technique and maintenance, and several external factors may pose a great threat of cracking in the concrete.

Cracks in concrete are a very common defect and are almost inevitable. However, the extent or degree to which cracks are formed can be controlled by various techniques.

 


 

  1. Types of Cracks in Concrete  

The common type of cracks in concrete can be summarized as follows:

 

  i. Plastic Shrinkage Crack  

Plastic Shrinkage Crack is developed during the initial stage itself i.e. before hardening. It is caused by a rapid loss of water from the surface of the concrete before it has been set

This crack generally occurs on horizontal surfaces than on vertical.

When the concrete is in the plastic state, before hardening, it contains enough water. Eventually, the water gets evaporated before setting; leaving behind voids between the aggregate particles. The voids or the empty spaces thus formed weaken the concrete increasing the possibility of cracking.

Such crack originates from the corner of slabs and spread throughout the thickness of the slab.

 

cracks in concrete

 

Causes of Plastic Shrinkage Crack

Plastic shrinkage crack is caused by a rapid loss of water from the surface of the concrete before it has been set.

The condition exists when the rate of evaporation of surface moisture exceeds the rate at which rising bleed water can replace it. Water receding below the concrete surface forms menisci between the particles of cement and aggregate causing a tensile force to develop in the surface layers. If the concrete surface has started to set and has developed sufficient tensile strength to resist tensile forces, cracks do not form.

The main causes of plastic shrinkage crack can be listed as follows:

1. Low relative humidity.

2. High ambient temperature.

3. High wind velocity.

 

Prevention of Plastic Shrinkage Crack

The various precautions that must be taken for preventing plastic shrinkage crack are mentioned below:

1. If a harsh climatic condition exists at the site such as high wind velocity, or hot temperature; the placement must be done at an appropriate time such as late evening or early night.

2. In very hot or dry conditions, fog sprays must be used. Fog spray reduces the rate of evaporation of water.

3. Proper workmanship, equipment, and materials must be ensured.

4. The concrete must be covered with wet burlap or polyethylene sheets between finishing operations.

 


 

  ii. Expansion Concrete Crack  

The cracks that are associated with the expansion of concrete are known as expansion concrete cracks.

These are the type of cracks that are formed as a result of the expansion of concrete, particularly in hot climatic conditions.

Due to the extreme heat, the concrete begins to expand and it pushes away anything present on its way such as a brick. Since neither of them can flex, the resulting expanding force is so strong that it can cause cracking of the concrete.

 

cracks in concrete

 

Causes of Expansion Concrete Crack

Some of the causes of the expansion of concrete cracks can be listed as follows:

1. Wrong choice of materials.

2. Excessive temperature fluctuations ( Alternate hot and cold cycle ).

3. Not using the appropriate methods for construction.

 

Prevention of Expansion Concrete Crack

Some of the preventive measures that must be adopted to prevent the cracking are as follows:

1. Application of expansion joints made up of asphalt, rubber, etc.

2. Selection of appropriate placement methods.

 


 

  iii. Heaving Concrete Cracks  

Due to the alternate freezing and thawing cycle, heaving concrete cracks are formed.

Normally, the ground rises when it freezes and settles back down during the thawing action.

In such conditions, if the concrete associated with the soil does not rise and subsequently settles down with the soil then cracks may develop in it.

Moreover, the deep spreading roots of trees may also cause a similar rise of the ground thereby forming heave cracks.

 

cracks in concrete

 

Causes of Heaving Concrete Cracks

Some of the causes of heaving concrete cracks can be listed as follows:

1. Alternate freezing and thawing cycle.

2. Roots of the trees.

3. Abnormal soil condition causing uplift.

 

Prevention of Heaving Concrete Cracks

Some of the preventive measures to prevent such cracks are as follows:

1. Adequate planning to minimize such causes.

2. Placing concrete in a suitable location as far as possible.

 


 

  iv. Settling Concrete Cracks  

Settling concrete cracks are the cracks that are associated with the settling of the soil.

It is the type of crack that is caused by the reverse action than heave cracks i.e. due to the settling of the soil.

As mentioned earlier, the roots of trees can be a prime source of the crack in the concrete. When a tree is uprooted, voids are formed between the concrete particles thereby forming cracks.

 

6 Types of Cracks in Concrete : With Causes & Prevention

 


 

  v. Concrete Cracks Due To Overloading   

Although concrete gains adequate strength after curing, cracks may develop on it if subjected to excessive load for a long time.

Such cracks on concrete that are formed due to the inability of concrete to withstand the excessive stress imposed are known as concrete cracks due to overloading.

 

6 Types of Cracks in Concrete : With Causes & Prevention

 

Causes of Concrete Cracks Due To Overloading

Some of the causes of such cracks are listed as follows:

1. Overloading on concrete.

2. Softening of concrete after heavy rainfall or snow.

3. Insufficient curing of concrete.

 

Prevention of Concrete Cracks Due To Overloading

Some of the preventive measures that can be adopted to avoid such cracks are as follows:

1. Adequate curing of concrete.

2. Proper maintenance of concrete particularly in harsh weather.

3. Avoid continuous overloading of concrete.

 


 

  vi. Concrete Crack Due To Premature Drying  

There are two types of cracks associated with premature drying i.e. crusting cracks and crazing cracks.

Crazing cracks are the type of cracks that appear as fine lines and mostly resemble a web of spiders.

On the other hand, crusting cracks are the type of cracks that occur due to the stamping process. The stamping process is the process of giving a certain texture to the concrete.

 

cracks in concrete

 

Causes of Concrete Crack Due To Premature Drying

Some of the causes of cracks due to premature drying can be listed as follows:

1. Improper mixing of concrete.

2. Excessive evaporation of moisture from the surface of the concrete.

3. The sunny or windy climatic condition that causes premature drying of concrete.

4. Improper stamping technique.

 

Prevention of Concrete Crack Due To Premature Drying

Some of the preventive measures that may be adopted to prevent such type of cracking can be listed below:

1. Use of a quality mix.

2. Proper workmanship.

3. Application of appropriate concrete finishing technique.

 


 

  2. Conclusion  

Most of the concrete cracks are the result of improper curing and improper mix.

So, curing should be done for a minimum of 14 days ( best to do for 28 days ).

Concrete mix design should be done according to the type of construction. This prevents overloading cracking and also increases the durability as well as the resistivity of concrete.

 

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