What are Cracks in Concrete ?

Cracks in Concrete is one of the most common thing which one sees in the different concrete members. Cracks in concrete is always misunderstood, as one finds its as a signal of fault or error in the construction of existing concrete member.

If you find cracks in concrete of your new built house, you should not panic because it is one of just those common things. Even though if you take the utmost precaution and care required for preventing cracks in concrete, there might be some cracks visible in you concrete structure with time.

The American Concrete Institute itself states that, ‘construction of concrete structure without some cracks is nearly impossible’. So next time if you see some cracks in your newly built dream house don’t panic, It can be cured with proper measures.

Causes of Cracks in Concrete

Shrinkage

Shrinkage is one of the major factor which causes cracks in concrete. When the concrete dries the water in it evaporates and the concrete dries and shrink rapidly, due to which the volume of concrete is gradually decreased which causes cracks.

The are 2 types of Shrinkage cracks :

• Plastic Shrinkage Cracks.
• Drying Shrinkage Cracks.

Temperature

Yes, you heard it right. Temperature also can be a cause of cracks in concrete. Sudden Difference in the temperature will result in the change of differential volume of concrete. As a result, When the capacity of tensile strain of concrete exceeds due to change in volume, it will develop cracks in concrete.

Chemical Reaction

When the aggregates used in the concrete contains active silica and due to the alkaline nature of cement hydration, there is an explosive chemical reaction which takes place slowly in the concrete, as a result of which cracks in concrete may be developed.

Poor Construction Practices

Adding excess amount of water in concrete to improve the workability is one of the most common practice followed on every site. Adding excess of water reduces strength of concrete and increases its drying shrinkage and settlement, due to which cracks can be formed in concrete.

Higher cement ration in concrete can also be one of the major cause of concrete cracks.

Lack and improper way of curing is one of the common cause of cracks in concrete.

Improper formwork or inadequate consolidation at the construction joints at the point of high stress can also lead to develop cracks in concrete.

Design and Detailing Error

There are many assets in design and detailing which can cause cracks in concrete mainly – Improper selection of materials, Lack of sufficient contraction joints, Improper design of foundation, Precast members and slab, Inadequate amount of reinforcement etc.

Construction Overloads

As the extra load is induced at the time of construction and when at the same time if formwork is removed at the early stage of concrete drying.

Corrosion of Reinforcement

Due to corrosion of steel the iron oxide and hydroxide in the steel gains greater volume than the metallic iron. This increased volume of reinforcement can cause cracks in concrete.

Improper selection of Cement

There are variety of cement grades available in market. Each grade of cement serves different strength requirement for the desired concrete member. If accurate and good quality of cement grade is not chosen for required strength of concrete then it may lead to cracks in concrete.

Preventive Measures to Minimize Concrete Cracks

• Use of rich concrete mixture should be minimized or avoided if possible.
• In the construction of masonry works use of lean cement mortar will prevent concrete cracks.
• Proper curing of concrete members should be done. Curing should be started immediately after drying of concrete to maintain the minimum moisture content in concrete.
• Water- Cement ratio should be minimum as it will increase the strength of concrete, Which will reduce concrete cracks.
• Concrete should not be dropped from height greater than 1.5 meter and should be properly placed. Vibrators should be used if necessary.
• The soil on which concrete is to be placed should be proper;y compacted as it will settle after sometime. As a result cracks may be developed on the surface of concrete.

Also read : What is Bleeding of Concrete ?