Porous Concrete/ Laboratory Versus Field Experience

Porous concrete is used as top layer on highway roads to obtain noise reducing and permeable pavements. An extensive laboratory investigation has been executed to obtain an optimum mixture composition for the use as top layer on highway roads. This comprises a good resistance against heavy traffic, no rooting and an optimum durability against frost actions with and without de-icing salts. The large porosity, up to 25% water accessible porosity, is obtained by a gap graded aggregate distribution. To obtain sufficient strength, polymer dispersion was added to the fresh mixture. The durability tests resulted in an optimum polymer-cement ratio, at which a good intermingling of the cement hydrates and the polymer film takes place after curing. The relation between the micro- and meso-structure of the porous concrete and the durability is established. To reveal the properties of porous concrete as top layer in the field, a test lane was constructed under the supervision of the Flemish Road Division. The application of porous concrete was done according to the wet-in-wet method. The test lane was part of a test project in which different top layers in concrete and in asphalt concrete were compared according to their physical, noise reducing and economical properties. This paper presents the data obtained from the laboratory study as well as some data obtained from the test lane. Emphasis is put on the resistance towards frost action with or without de-icing salts in relation to polymer modification and to the open structure of porous concrete.