Is slurry seal the same thing as sealcoat?
Here, yes. Super Seal 100 is one product with two names: contractors in Montana and Washington order it as slurry seal, and North Idaho calls the same tank sealcoat. It is an asphalt-emulsion pavement sealer, mixed at our yard in Rathdrum, Idaho, and sold in bulk.
What is in it?
Three things, each with a job. Asphalt emulsion is the binder: it bonds to the mat and stays flexible through a freeze-thaw cycle instead of going brittle on it. Sand is the wear surface: it takes the traffic and puts texture back on a slick, polished lot. Bentonite clay is the suspension: it holds the sand in the mix from the plant to your job.
The sand and the clay are in the tank when you load it; you are not finishing a concentrate in the truck.
Is it asphalt emulsion or coal tar?
Asphalt emulsion. That is the same chemistry as the pavement it goes on, which is why an asphalt-based sealer bonds to the mat and stays flexible after it cures — it moves with the surface through freeze-thaw instead of cracking over it.
Why is there sand in it?
Sand is what a sealed surface wears on. An emulsion film with no aggregate in it is slick when it is wet and wears through under tires; the sand gives the film traction and body and takes the traffic so the binder does not have to. In Super Seal 100 the sand goes in at the plant, and the bentonite is there to keep it from settling out between our tank and yours.
What does the bentonite clay do?
It keeps the sand in suspension. A clay-stabilized emulsion thickens when it stands and loosens when it moves, so the sand stays distributed through the mix instead of dropping to the bottom of the tank. That is also why the storage rule is what it is: an agitated tank, mixed weekly.