If concrete is impervious, or in other words, its permeability is not high then acidic agents and corrosive agents cannot infiltrate and attack it. Concrete usually has two varieties of pores, which establish extend of permeability. These are known as capillary pores (with a width ranging between 0.01 to 10 micron) in the cement, paste which coats the totals and bigger micro voids, between 1 mm to 10 mm, which are resulted by the defective compaction/compression of fresh concrete.
When voids/hollows are interlinked due to their bigger number and volume a unremitting link is created, which results in the concrete being permeable.
Factors affecting Permeability
- Water and cement ratio
- Compaction and curing
In the figure below, we can see that each factor is evenly important. If any one of these factors is not controlled. It leads to augmentation of permeability.
We can see that the level of permeability is amplified as the cement and water’s ratio is increased. Basically, at the cement and water ratio of approximately 0.4, permeability is basically 0.
In accordance with the tests that were undertaken to decide the consequence of superplasticisers on water permeability, 150 mm size cubes water stored for 30 days in lime- immersed water at 230C and then exposed to water pressure on one side.