Table of Contents

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 typeBinderBinder factor(1)
Conventional sealC170, C240, C3201.0
Unmodified emulsion sealConventional emulsion (60%)1.0
High bitumen content emulsion (≥ 67%)1.1
Modified emulsion sealUser binder factors below for the PMB that has been emulsified
High stress seal (HSS2)S10E, S15E, S35E1.0
S20E, S45R, S15RF1.1
Extreme stress seal (XSS)S20E1.1
S45R, S15RF1.1
Strain alleviating membrane (SAM)S10E, S15E, S35E, S20E1.1
S45R, S15RF1.1
  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.