Fundamental of Cracking of Immature Concrete

Cracking of immature concrete cab observed if it is not treated according to the technical requirements specified in the project specification or as advised by the senior engineer who has the knowledge in this subject.

Cracking of immature concrete can be due to higher internal temperature, higher temperature gradient and a higher difference in the surface and core temperatures.

In addition to the above, it should be noted that the increase of the core temperature above a certain level(generally around 70 Celsius) leads to the formation of delayed ettringite. This is a long term effect on the concrete. This process will increase the internal volume of concrete and it leads to internal cracking of concrete.

There are different methods used to minimize the craking 

• The common practice is to limit the temperature difference between the external concrete surface and the core to Celsius 20. However, in some projects, this value is kept at Celsius 25 considering the scale and type of concrete to be used.
• Further, the temperature gradient is not allowed to exceed Celsius 25 per linear meter. If the construction is done by adhering to above, concrete cracking of early age can be minimized.

It should be noted that it is of prime importance to stick to the recommendations given in the mockup test. The exact thickness of formwork and types used for the mockup test shall also be used for the construction work.

Thin concrete can be done without adhering to the above comment as the heat of hydration is comparatively smaller.

However, there could be cracks in the concrete surfaces due to inadequate curing. Concrete surfaces shall not be exposed to the environment, which varies the temperature and humidity. When the concrete surface is exposed to the environment, concrete will get dried due to the evaporation of the water in the concrete of which eventually lead to cracking of concrete.

Further, there are different article namely Effect of Construction Practices on Cracking, Cracking of Concrete, Thermal Cracking of Concrete, etc. written in this subject.