The excellent qualities of pervious wearing courses which enhance road safety and comfort are well known. However, there are very few test and control methods which allow these courses to be planned and used adequately. The design of the porous asphalts used in the construction of these pervious wearing courses depends on a number of rules of thumb derived from their use, but there is no test method or procedure which might allow their properties to be characterized and optimized.
In this paper, we describe the procedure and planning criteria which are used in Spain in the design of porous mixes and which were established both from the behavior of these mixes in use and from the results of tests performed in the laboratory. The procedure used is based on optimizing two fundamental characteristics of these mixes: permeability and resistance to disintegration. We have developed two testing methods which allow both properties to be assessed. Permeability is assessed in situ by means of the Laboratorió de Caminos de Santander (LCS) permeameter and resistance to disintegration is evaluated by means of the Cantabrian abrasion loss test. These two tests optimize the design of these mixes and allow the effect on their behavior of using modified binders to be evaluated. We also describe the effects that these mixes have on adhesion, texture, and noise of the wearing course surface compared with other materials used in road surfacing.