Pavement

The design aggregate spread rates for single/single seals to produce a satisfactory aggregate mosaic are shown in Table 6.8.

To achieve a satisfactory mosaic and to avoid binder pick-up using low viscosity binders and emulsion binders, the aggregate spread rate needs to be heavier than for other binders.

Table 6.9 provides the aggregate spread rate for a scatter coat of small-sized aggregate. A scatter coat is sometimes used with single/single seals to reduce the risk of aggregates being dislodged by traffic during initial trafficking. It is particularly useful when using emulsion binders to overcome the low cohesion during the curing period.

For strain alleviating membrane interlayers (SAMI), the aggregate spread rate needs to be lighter than for conventional bitumen and multigrade binders to enable interlock between the seal and the overlying asphalt mix (Table 6.10).