7.1.2 Initial Seals
Preparation of the pavement basecourse is critically important to achieving a consistent high standard of initial seal.
The success of an initial seal relies on the binder adhering to the basecourse, and anything that impedes this process should be avoided. Sweeping is important to expose the stone mosaic of the larger aggregates within the basecourse material which facilitates bonding of a binder to the prepared basecourse, especially more viscous or emulsion binders. Guidance on surface preparation (homogeneity, exposed aggregate, avoidance of laminating materials or a build-up of fines) is provided in Austroads (2009b).
Surfaces to be initial sealed should be kept slightly damp, but not wet. A wet pavement may result in aggregate embedment and flushing in the wheelpaths. A dry surface may prevent the binder from properly ‘wetting’ and bonding to the pavement surface. Where the pavement surface is excessively dry a water tanker should be used to lightly dampen the surface.