5.4 Surface Texture
The existing texture of the surface to be sealed is an important consideration in sprayed seal design.
An allowance (Section 6.2.2) is added or subtracted to the binder application rate based on the measurement of the surface texture by the sand patch method, using Austroads (2008).
Surface texture data is also commonly collected on network-level surveys with laser profilometers, as described in Austroads (2016), however the surface texture reported by these methods may not be equivalent to the sand patch results, and should only be used for seal design purposes where a correlation exists between the sand patch and the particular measurement device is provided.
The existing surface texture, and the size of the aggregate on an existing surface contribute to selecting the size of an aggregate to be used in sprayed sealing. Guidance for selecting appropriate aggregate sizes is provided in Table 4.3.