Table of Contents

4.8.2 Aggregate Size

The choice of aggregate size depends on traffic, life expectancy and climatic conditions.

For single/single initial seals, 7 and 10 mm aggregates are appropriate for low‑traffic applications, and can be used successfully for higher-traffic applications in the absence of conditions such as high‑stress traffic movements, extreme heat, or predominantly wet conditions.

The 14 mm aggregates are not recommended for single/single initial seals. There is an increased risk of unsatisfactory performance with this type of treatment, and it should only be used when there are special requirements that demand it. It is not recommended for high-traffic applications. A binder with adequately high viscosity will be necessary to allow the binder to successfully retain the aggregate, but it is unlikely to have adequate bonding with the base.

Double/double initial seals, or single/single initial seals incorporating a scatter coat, are useful for high‑traffic, high‑stress sites. Various aggregate sizes can be used for double/double seals, with 10/5, 10/7 and 14/7 mm combinations being common choices.