6.1.1 Basic Voids Factor
The basic voids factor, Vf (L/m2/mm), is related to traffic volume. It is critical that the traffic volume used in the design is representative of the actual traffic on the area being considered, as the volume and composition of traffic has a direct effect on the performance of a sprayed seal (Section 5.2).
For single/single seals, Vf is determined from Figure 6.1 or Figure 6.2 (depending on the traffic volume). The central target line is used to determine Vf in all cases. Figure 6.1 and Figure 6.2 also contain lower and upper limits that represent indicative confidence limits for the Design Voids Factor, VF, after applying aggregate and traffic adjustments to Vf.
For double/double seals, Vf is determined from Figure 6.3 or Figure 6.4 (depending on the traffic volume). The voids relationship in the first application/layer seal of a double/double seal is affected by the use of the smaller aggregate in the second application, which partially fills and therefore reduces the air voids. This is compensated for by using a reduced basic voids factor for this first application/layer.
In all cases, Vf should be read to the nearest 0.01 L/m2/mm.
Figure 6.1: Basic voids factor (Vf) for single/single seal – traffic volume 0 to 500 vehicles/lane/day
Figure 6.2: Basic voids factor (Vf) for single/single seal – traffic volume 500 to 10 000 vehicles/lane/day
Figure 6.3: Basic voids factor (Vf) for double/double seal – traffic volume 0 to 500 vehicles/lane/day
Figure 6.4: Basic voids factor (Vf) for double/double seal – traffic volume 500 to 15 000 vehicles/lane/day
