WHAT A POLYMER BLENDING SYSTEM DOES
- It mixes virgin AC (asphalt cement) with a polymer.
- Mixture is known as PMAC (Polymer Modified Asphalt Cement).
- Mixture is used to make the road paving material known as HMA (hot mix asphalt).
- HMA is a mixture of aggregates bound together with asphalt cement.
- Using polymer to make HMA is a relatively new development of the past two decades.
WHY MIX POLYMER WITH ASPHALT?
- Polymer enhances the properties of asphalt cement.
- Increases the service life of highway surfaces.
- The surface is more stable at warmer temperatures and more flexible at colder temperatures.
- Reduces costs for road repair and replacement.
- Motorists enjoy smoother ride and their vehicles last longer.
- Usage has increased dramatically in last few years.
- Now mandated for most state and federal highways throughout the U.S.
WHAT IS POLYMER?
- A polymer is simply two or more monomers linked together.
- Examples are rubber, rayon, polyethylene, nylon, vinyl, Styrofoam, polystyrene.
- Not all are suitable for mixing with asphalt cement for road building.
- The polymer most commonly used for road building is SBS.
- It is usually comes in the form of small pellets or granules (shown here).
WHAT IS SBS?
- It is the monomer styrene linked with the monomer butadiene to form a new giant molecule: styrene-butadiene-styrene or SBS.
- It withstands high temperatures and extreme tearing forces.
- These are ideal characteristics for a polymer that is to be added to AC.
- Another polymer often used to make PMAC is GTR (ground tire rubber) shown here.
- It has characteristics similar to SBS.
POLYMER SYSTEM COMPONENTS
- Storage tanks for virgin AC used for blending.
- Mixing tanks where polymer pellets are added to the AC.
- Box dumper for loading boxed polymer pellets into the hopper.
- Hoisting system for loading bagged polymer into the hopper.
- Hopper for polymer pellets.
- Augur that transports pellets to a mix tank.
- A mill that grinds the pellets while mixing into fine particles for a more uniform mixture.
- Let-down tanks that store and stir the mixture as additional virgin AC is added.
- A thermal-fluid heating system that heats the tanks.
- Electrical power panel with operator controls.
- Heatec has built a wide variety of polymer and rubber blending systems over almost two decades.
- Used primarily at asphalt terminals throughout the U.S. and at a several overseas locations.
- Also used at facilities that make roofing shingles.
- Most use stationary polymer blending systems.
- Fully portable system are also available.
- Also available are compact skid mounted systems suitable for delivery in an overseas shipping container.
- The latest systems offer both automated and manually operated controls.