Sweet emulsion
By Mike Beavin
Heat (hot mix) and water (emulsion) are the two primary ways to deliver an asphalt binder to where it needs to go.
Hot mix is tried and true. In fact, after WW2, it was the only government-sanctioned way to pave for the construction of the U.S. interstate system.
Did you know that your favorite interstate was probably not built to lay down a straighter, smoother ride to Grandma's for the holidays? More likely, it was part of the 1956 “National System of Interstate and Defense Highways” bill signed by President Dwight Eisenhower. Grandma was happy, I’m sure, but a more efficient way to protect us in the event of an atomic attack was more the point of this legislation.
We knew hot mix. The first discussion of paving our roads with it started around 1890 and the idea of using emulsions wasn't new. In fact, there are volumes of information about using water to liquify a binder dating back to the early thirties, but the idea of using it to pave roads was in its infancy, so the politicians went with what we knew and the interstates were constructed with hot mix. Farmers and commuters must have been pretty darn happy to see roads that used to go axle deep in mud in the spring transform into reliable and flat ways to carry crops to market, get to the office on time and, of course, visit Grandma.
What about water? Heat works, but so does water. Really well! My mind was blown when I discovered some old, thick technical paper compilations from the 1930s in the Asphalt Institute library that went WAY beyond what I imagined could have been possible at that point in history. They included asphalt emulsion particle size analysis, rheology testing on the residue 50 years BEFORE the first modern DSR was developed.
Here we are. Summer of 2019. Now we know, water can do anything heat does to deliver a binder to its intended destination and do it well but asphalt emulsion had a rough start. World War 2 and the construction of the interstate system suppressed the use of emulsions for decades and resulted in a general lack of understanding of them. This eventually contributed to a proliferation of ways to characterize emulsions and, because of that, emulsions are still the ‘wild west’ of laboratory testing. An emulsified asphalt binder is nothing but binder and water in a mechanical and chemical marriage. The residue should deliver the same performance as a PG binder. But the tests we use to characterize it suffer from a lack of sophistication and consistency.
The Asphalt Institute has enjoyed success with our National Binder Technician Certification program. The program helped deliver a standard best-practice to binder technicians. After certifying over 420 technicians, we recognized that heat is not the only way to deliver that beautiful, black, sticky stuff.
Asphalt emulsions are no less premium products than PG grade binders but, in some ways, we are treating them like they are. Technicians now have the opportunity to seek certification and help standardize the way we characterize asphalt emulsions in the laboratory. Sweet emulsion? Let’s treat it that way.
TECH TIP
Sticky binder floors no more
Binder burps, break-down blunders and BBR beam breaks. All of these common binder lab floor polluters create droplets, drips and shards of sticky binder that share a nasty habit if not quickly cleaned: They hitch rides home with you on the soles of your shoes.
Once there, there are rugs, chairs and (noooo) the clothes dryer to cling to. Perhaps the first clue of their unwanted presence in your inner sanctum is when your husband, wife or significant other slowly turns their gaze upon you. They had been staring at something. You have unwittingly become the Trojan horse to a binder nugget and it has made itself comfy, ground securely into your carpet.
This didn’t have to happen! Even the most OCD clean-freak binder technician knows that keeping a floor in a lab that specializes in sticky stuff, clean isn’t easy but we’ve got you! Stop what you are doing and head to just about any grocery or hardware store and pick up a Swiffer-type dry sweeper. Scrape up what binder you can first. Then, put a small squirt of your solvent-of-choice on the pad and a few easy swipes later, that sticky drip is history. Toss the pad in the trash and go home to a nice hug instead of an accusing glare.
- Mike Beavin, Asphalt Institute Technical Training Coordinator
TECHNICIAN SPOTLIGHT
Daniel Dahms
Alaska DOT
Materials Laboratory Technician
Daniel has been working with asphalt quality control for two years. He performs asphalt binder testing on the job.
He really enjoys working with the development of new asphalt products and educating team members about the cost of poor quality.
"The NBTC program helped me learn the tips and tricks of the trade that you would not normally get just reading through the standards. The program is taught by the most knowledgeable people in the industry and this program is essential for anyone who is testing asphalt binder on a regular basis," said Dahms.