Differences between volumetric and areal porosities within different vertical regions of permeable concrete pavement

This study quantitatively showed the differences between volumetric and areal porosities versus the number of applied areal porosities within different vertical regions, and a suitable number of applied areal porosities was proposed to accurately represent the volumetric porosity. The volumetric or areal porosities within five equal vertical regions from each specimen were determined using the slice-water displacement method, slice-image analysis, or computed tomography (CT) scanning. The measurements indicated that near the top or bottom surface, the porosity increased sharply as the surface was approached because of wall effects. The boundary of the region influenced by wall effects is located 1.70-2.36 mm from the top or bottom surface. The wall effect-caused increased porosities range from 1.09% to 1.51% for the top region, whereas they range from 0.51% to 0.73% for the bottom region. For the five regions and the complete specimen, the differences between volumetric and areal porosities and their fluctuations were typically larger when the number of applied areal porosities was fewer, and the maximum absolute differences were well fit by decreasing power curves.