Technical Questions

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The relationship between porosity and permeability of concrete

Q. What is porosity and is it related to permeability of concrete?


A. Porosity is a measure of the volume of voids in concrete. Permeability is the rate of flow of moisture through concrete under a pressure gradient. Voids through which moisture can move must be interconnected and of a certain size. Discontinuous pores and pores with narrow entrances retard flow of moisture. In a mature, well-cured, well-proportioned paste (low w/cm), permeability would be low, even if high porosity exists. Concrete that is more porous tends to be more permeable.


References: SP-1(02); ACI 201.1R-08; ASTM C1202

Topics in Concrete: Concrete Fundamentals; Durability; Permeability

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