6.3.2 Double/double Seals
Double/double seals are strong robust seals by virtue of the mechanical interlock of the large and smaller aggregates and are not as reliant on the binder as a single/single seal to cope with high traffic stress. Binder factors for double/double seals (Table 6.5) are thus reduced compared to those used for single/single seals.
Table 6.5: Binder factors for double/double seals
| Treatment type | Binder | Binder factor(1) |
|---|---|---|
| Conventional seal | C170, C240, C320 | 1.0 |
| M500 | 1.1 | |
| Unmodified emulsion seal | Conventional emulsion (60%) | 1.0 |
| High bitumen content emulsion (≥ 67%) | 1.1 | |
| Modified emulsion seal | User binder factors below for the PMB that has been emulsified | |
| High stress seal (HSS2) | S10E, S15E, S35E | 1.0 |
| S20E, S45R, S15RF | 1.1 | |
| Extreme stress seal (XSS) | S20E | 1.1 |
| S45R, S15RF | 1.1 | |
| Strain alleviating membrane (SAM) | S10E, S15E, S35E, S20E | 1.1 |
| S45R, S15RF | 1.1 | |
- Under very heavy traffic conditions with high percentages of heavy vehicles these factors may be reduced by 0.1 but should not reduce the binder factor to less than 1.0.