How to Manage Asphalt Poxing (Dust Ball) Defects
Asphalt poxing defects (otherwise known as "dust balls") occur when balls of bitumen coated dust form during the manufacturing processes or paving processes. These defects can be caused by a variety of factors, including:
a) Moisture induced clumps of fine aggregates whilst in storage, and hardened during the plant batching process.
b) Running the plant aggregate feeds on bypass with insufficient pre-screening.
c) Poor compaction of the asphalt during construction, consequentially 'exploding' under traffic once pavements cools.
d) Potentially other foreign materials such as dirt finding their way into the asphalt paving process.
c) Presence of certain types of aggregates in the asphalt design mix, for example open grade OG asphalt has negligable fine aggregates, compared to Dense Grade and EME asphalt designs.
To manage asphalt dust ball defects, the following steps can be taken:
Identify the cause of the defects and make sure to fix it before doing any maintenance, whether it's the type of asphalt mix or the compaction process.
Regularly sweeping and cleaning the affected area to remove loose dust and debris.
Applying a dust-control agent to the surface of the asphalt or haul routes, which can help to bind the dust particles together and reduce the formation of foreign debris or asphalt pox spots.
Consider milling off the poxed surface of the concerning asphalt layers, and then re-paving the concerning area - hopefully with the asphalt contractors warranty, if your project contract requires it.
Scheduling additional asphalt surveillance (plant operations and site inspections), especially arranging a close inspection of the asphalt surface after pavement runs and heavily loads for several days between paving runs - dust balls should start to pop after several days or a week of heavy load.
Note that it is important to work through any poxing defects with your pavement supplier and your technical resources, who can help you assess the specific issues and develop a plan to manage the dust ball defects with client knowledge.
Why should the asset owner accept dust balls that may form like "chicken pox" and eventually explode into road potholes?