Permeability is defined as the property that governs the rate of flow of a fluid into a porous solid. If concrete is impermeable, corrosive agents cannot penetrate and attack it. Concrete basically has two types of pores, which determine permeability. These are capillary pores (with a diameter varying between 0.01 to 10 micron)

in the cement paste which coats the aggregates and larger microvoids, between 1 mm to 10 mm, which are caused by faulty compaction of fresh concrete. When voids are interconnected because of their larger number and size a continuous link is formed, which makes the concrete permeable.

Factors affecting permeability of concrete

1- Water-Cement Ratio

2- Improper Compaction of Concrete

3- Improper Curing

4- Age of concrete

5- Pore structure

6- Degree of compaction

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