Goseeko blog

What is Shrinkage ?

by Pratiksha

Shrinkage is the decrease in volume of concrete in the absence of load with time. In the plastic stage concrete shrinks in volume due to absorption of water or loss of water.

Due to bleeding the surface water evaporates rapidly causing and this uneven shrinkage causes shrinkage cracks. It is depends upon the efficiency of the curing method as well as water cement ratio, cement lean mixes and amount of water added.

It can be reduced by using low water cement ratio, presaturated aggregate, watertight and non absorbent.

Factors Affecting:

  1. Water cement ratio
  2. Cement type and content
  3. Ambient humidity
  4. Type of aggregate and content
  5. Admixtur

1. Water cement ratio

It increases with the increase in water cement ratio.

2. Cement type and Content

Rapid hardening cement gains strength rapidly and hence shrinks more than ordinary portland cement. The shrinkage increases with the increase in cement content.

3. Ambient Humidity

The shrinkage increases with the decrease in humidity

4. Type of aggregate and content

Aggregates restrain the extent of shrinkage in concrete hence concrete with larger aggregate content produces less.

5. Admixture

Firstly shrinkage increases with addition of calcium chloride and reduces with lime replacement

Types of Shrinkage :

  1. Plastic
  2. Drying
  3. Carbonation
  4. Autogenous

1. Plastic

If the volume reduction in concrete occurs before it becomes hard or still in plastic stage it is called plastic .

2. Drying

The reduction in volume of concrete that occurs preliminary due to moisture loss after the concrete has hardened is known as drying .

3. Carbonation

Carbon dioxide reacts with the moisture present in the atmosphere forming carbonic acid which then react with to form calcium carbonate and some other cement compounds are also decomposed.

4. Autogenous

In the sealed concrete the macroscopic volume change occurring with no moisture movement to or from the paste is called autogenous.

You may also like