Shrinkage Effect of concrete

Shrinkage Effect on Concrete

Shrinkage Effect on Concrete

Shrinkage is the property effects of concrete to change in volume independently of the loads it sustains. Shrinkage phenomenon can cause working of slabs on grade due to differential drying and increased deflections of non-symmetrically reinforced concrete elements. Shrinkage is affected by a number of factors that include time, Stress-intensity, temperature and humidity, type of mix, the geometry of the concrete element, and many others.

Factors which affect the shrinkage of concrete

Shrinkage effect on concrete

• Aggregate
• Modulus of Elasticity
• Aggregate content.
• Cement 
• water-cement Ratio
• Cement Content
• Humidity
• Moisture condition
• The geometry of the Concrete Element
• Temperature

1. Aggregate

• Modulus of Elasticity
• Aggregate content

Any increment of these two factors will reduce the drying shrinkage and creep of a prospective concrete. The Modulus of elasticity of aggregate controls the amount of creep and concretes made with different aggregate exhibit creep of varying magnitudes. The shrinkage that takes place after the concrete has set and hardened is called drying shrinkage and most of it takes place in the first few months.

• Cement

• Water-cement ratio

Creep is closely related to the water-cement ratio. For a given cement content, increase in water, increase in water-cement ratio will increase both drying-shrinkage and creep.

• Cement Content

For a given water-cement ratio increase in cement content will reduce the creep but will increase the drying shrinkage.

• Humidity

If there is an increase in the relative humidity of the air, both the drying shrinkage and the creep will increase.

• Moisture condition

When a concrete structural element is dried under load the creep that occurs may be one to two times as large as it would be under constant moisture conditions.

• The geometry of the Concrete Element

It has been observed that an increase in the theoretical thickness of the concrete element reduces the drying shrinkage and creep.

• Temperature

If the two concrete has the same curing history, The one that is kept in a higher temperature will have more creep and drying shrinkage than the other one kept at a lower temperature.