2.3.2 Influence of openings ratio
The research of Borgwardt (1995) and Breuste et al. (1996) states that a correlation between openings ratio and infiltration rate is not valid in the aged condition. A high percentage of openings is thus only an indicator for a good infiltration, if the fines content is at the same time low. Is the clogging over the years in progress, the permeability of the pores is affected unattached from the openings ratio. New permeable pavements with openings fillings of crushed gravel 2/5 mm view at least a significant increase of the infiltration rate with advancing openings ratio and a relative high performance with 10 % or more openings ratio (Fig. 5).