Concrete form liner

A concrete form liner for lining a concrete form and containing a concrete mixture poured into the concrete form during the manufacture of a concrete article, comprising:

• a microporous membrane having pores that transmit at least 1 liter of water per square meter of the membrane during 30 minutes when the water is under a hydrostatic head of 1 cm, but which pores prevent the passage of at least 99% of particles with a diameter larger than 2 microns in water under a hydrostatic head of 150 cm, said microporous membrane having a first side and an opposite second side;
• a porous sheet having a first side and an opposite second side, said second side of said porous sheet juxtaposed with said first side of said microporous membrane, said porous sheet having at least one layer of pores 95% of which have a diameter in the range of 0.2 microns to 60 microns, which layer is coextensive with the porous sheet, the air permeability of said porous sheet, measured according to ASTM D 737 at a pressure of 500 Pa, being at least 5 times greater than the air permeability of the microporous membrane, measured according to ASTM D 737 at a pressure of 500 Pa;
• wherein said concrete form liner is permeable to air and water in a concrete mixture poured against the first side of said porous sheet, but is substantially impermeable to particles in the concrete mixture of at least 2 microns in diameter.