Appendix F 3.2 Adjustments to the Basic Voids Factor
The design voids factor, VF (L/m2/mm), is determined by adjusting the basic voids factor (Vf) to account for abnormal aggregate shape (Va) and effect of traffic (Vt). These factors may be positive or negative and are cumulative.
Adjustment for aggregate shape (Va)
|Aggregate type||Aggregate shape||Flakiness index (%)||Shape adjustment Va|
|Crushed or partly crushed||Very flaky||> 35||Considered too flaky and not recommended for sealing|
|Flaky||26 to 35||–0.01|
|Angular||16 to 25||Nil|
|Cubic||10 to 15||+0.01|
|Very cubic(1)||< 10||+0.02|
- Not recommended for bottom layer of D/D seal as insufficient angularity does not promote interlock with top layer.
Adjustment for traffic effects (Vt)
|Traffic||Adjustment to basic voids factor (L/m2/mm)|
|Flat or downhill||Slow moving – climbing lanes|
|On overtaking lanes of multi-lane rural roads where traffic is mainly cars with ≤ 10% of HV||+0.01||0.00||n.a.||n.a.|
|Non-trafficked areas such as shoulders, medians, parking areas||+0.02||n.a.||n.a.||n.a.|
|0 to 15 (EHV(%))||Nil||–0.01||–0.01||–0.02|
|16 to 25 EHV(%)||–0.01||–0.02||–0.02||–0.03|
|26 to 45 EHV(%)||–0.02||–0.03||–0.03||–0.04|
|46 to 65 EHV(%)||–0.03||–0.04||–0.04||–0.05|
|> 65 EHV(%)||Use the process described in Section 5.2.7 for access roads to quarries, mining locations, etc.|
n.a. Not applicable
* Channelisation – a system of controlling traffic by the introduction of an island or islands, or markings on a carriageway to direct traffic into predetermined paths, usually at an intersection or junction. This also applies to approaches to bridges and narrow culverts.