Loss of Aggregate

There are several major causes for serious loss of cover aggregate from surface treatments and seal coats as shown in Figure 1-1:
  • A long delay between spraying binder and spreading cover aggregate, causing the binder to become chilled and hardened.
  • Sealing too late in the season. Seal coats tend to perform better if they are under traffic a few months prior to winter weather.
  • Insufficient binder is provided to cement the cover aggregate into place.
  • Selection of an improper binder for prevailing conditions.
  • A coating of dust or film of moisture on aggregate particles affects the adhesion to the binder.
  • Fast traffic is permitted before adhesion is fully developed.
  • A rainstorm occurs prior to development of adhesion.
  • Placement of too much aggregate may cause embedded aggregate to dislodge under traffic.
    Seal coat pavement surface exhibiting aggregateloss. (click in image to see full-size image)
    Figure 1-2. Seal coat pavement surface exhibiting aggregate loss.