Surface Dressing failures on roads - Fatting up - Causes

SURFACE DRESSING  FAILURE - "FATTING UP" - CAUSES

PURPOSE

The object of surface dressing is to create a stable mosaic of chippings securely attached to the road surface, this provides a comprehensive seal to prevent the ingress of water in to the road pavement, and a fresh hard wearing, well textured, skid resistant surface,This is achieved by spraying the correct amount of bitumen onto the road surface followed by the appropriate amount of the correct size of chippings according to the softness of the road surface.

POSSIBLE CAUSES OF "FATTING UP" Wrong assessment of road hardness Too high a rate of spread of bitumen, and there can be a number of reason for this other than poor design Incorrectly calibrated "fifth wheel" or speedometer of spraying vehicle Incorrect speed chart for binder sprayer, Incorrect tank pressure Change in the base viscosity of the binder, Change in the spraying viscosity of the binder Using a smaller chipping than the road hardness testing indicated Roads where surface dressing as been the only maintenance treatment for many years. Roads where the underlying bituminous material has a low viscosity (i.e. high penetration grade or cut-back binder, this can often show itself in patches where a bituminous mixture with a cutback binder has been used for ease of laying by hand.