When an asphalt emulsion is sprayed onto a surface, its droplets start to coalesce as water evaporates or the emulsifier reacts with the aggregate, and that change is the break. The color shift from chocolate brown to black is the field signal. After the break the residue still has to set and cure as the last water leaves, which takes anywhere from minutes to hours depending on emulsion grade, temperature, humidity and wind.
Hold the trucks, that tack's still brown, give it a few more minutes to break or they'll track it up the whole lane.
Rapid-setting grades can break in under a minute in summer sun, while slow-setting tack on a cool, damp morning can sit brown for half an hour.
Also heard as
- breaking
Related terms
Asphalt emulsion
Asphalt binder broken into tiny droplets and suspended in water with an emulsifier so it can be sprayed cool.
Tack coat
A thin spray of asphalt between layers that bonds the new lift to the surface underneath.
Prime coat
A low-viscosity asphalt sprayed onto granular base to soak in, seal it and bind loose surface particles before paving.