St. Thomas in the Virgin Islands has it. Utah, New Mexico, and South Dakota have all used it. What is it? Washington Rock’s Armorstone.
What exactly is Armorstone, and why do so many states around the US go to the trouble of getting it all the way from Washington State?
Let’s start with the why.
Why Do State Agencies Use Armorstone?
Think of it this way: if you could prevent accidents, reduce the amount of time it takes to repair a road, and extend the life of a road, would you?
Of course—and that’s what state agencies are doing. They pour a super glue-like liquid called epoxy on top of roads and add thousands of small, hard stones to the surface. When the epoxy dries, the surface becomes extremely hard.
This process is called an overlay, and it has a lot of benefits:
- Road protection. The epoxy prevents things like road salt from damaging the road. Overlays add 10-15 years to the life of the road.
- Accident prevention. The small stones help cars grip the road better, leading to fewer accidents.
- Time and Cost Savings. Crews can complete road patches quickly, avoiding extensive traffic delays. It’s cheaper and easier to do an overlay than to chip and repave existing asphalt.
So, how does Armorstone fit into this picture?
What is Armorstone?
Armorstone is the small, hard rock placed on top of the epoxy. It’s also known as an overlay aggregate. It’s a 7 on the Mohs hardness scale (a diamond is a 10).
Many states have their own ideas about how they want their Armorstone to look. Sometimes they want it to look like sand. Sometimes they want it to be the size of a dime. So Washington Rock makes many different kinds of Armorstone, and each kind has its own name.
Crack Seal Sand
#8 x #14
Crack Seal Sand
#14 x #50
#4 x #16
#6 x #16
#4 x #16
Different Roads, Different Applications
There are a lot of ways to use epoxy and Armorstone together. Here are the basic treatments state agencies use.
A single coat of epoxy is applied to the road surface and covered in overlay aggregate. Stones are typically ¼”. HFST increases the safety of roads, such as shoulders where cars skid out.
Two coats of epoxy are applied to the road and then covered in overlay aggregate. Stones are typically 3/8”-1/2”. This technique prevents things like road salt from eroding the interior structure of the concrete. The addition of epoxy will add 10-15 years to the lifespan of the road.
Sand and pea gravel are mixed with epoxy to patch roads. The concrete sets up more quickly than traditional concrete, and the patching is impermeable (in other words, it prevents water from soaking into the road).
A runny epoxy is used to fill cracks, and then it’s topped with wearing course to add grip to the surface.