Understanding Your Emulsions
Asphalt emulsions are used in many pavement preservation methods such as pothole patching, micro-surfacing, chip seal, fog seal, and crack filling, but keeping emulsion intact during transport to a job site can be critical to a successful result. Understanding the properties of the emulsion can make or break the results of any application. Emulsion is a homogeneous mixture of two immiscible liquids such as asphalt and water. These two materials are put through a high shear mill with an emulsifier chemical and the result is an asphalt emulsion. The following chart from A Basic Asphalt Emulsion Manual, by the Asphalt Institute and the AEMA lists the types of anionic and cationic emulsions.
Asphalt emulsions come in two different types; Anionic and Cationic. Designations of the different types of emulsions can change for different states and regions, so it is important to ask questions and determine which type of emulsion will perform best for your application.
Anionic asphalt emulsions are abbreviated with the following:
RS = Rapid Set
- Have short storage lives, ideally manufactured within a day or two of use.
- Have low pump stability, do not recirculate through pumps unless necessary
- Have very fast curing properties. Best for quick return to sealing type applications where a film layer of asphalt is needed with quick return to traffic.
- The most delicate of the emulsions, requires gentle handling
- Not suitable for mixing with aggregate
HFRS = High Float Rapid Set
- Handles similarly to RS
MS = Medium Set
- More storage stability than RS/CRS, can be stored for several days
- Better pump stability than RS/CRS, can be pumped more but should still be minimized
- Can be used in mixing type applications such as slurry
SS = Slow Set
- Most storage stability, can be stored for weeks before application
- Most pump stability, can usually be pumped as much as needed
- Used for mixing type applications and where cure time and early strength is not important
Cationic asphalt emulsions are abbreviated with the following and behave as described for each abbreviation above:
CRS = Cationic Rapid Set
CMS = Cationic Medium Set
CSS = Cationic Slow Set
Depending on the type of aggregate, road surface, pavement preservation technique, and availability of emulsion, any of these types of emulsion can be transported to a job site. The chemical nature of the type of emulsion being used is important to know, so that the emulsion stays in-tact and does not break.
Many factors can contribute to emulsion breaking prior to use on the road surface, but when an emulsion breaks, the asphalt component bonds to the nearest surfaces. In pavement preservation, the break needs to occur after the application of the emulsion to ensure a strong chemical bond with the road surface and aggregate. Cationic and Anionic emulsions should never be mixed, because the emulsion will become unstable and break nearly immediately causing issues with your equipment. Over-pumping or over-mixing results in shear stress to the asphalt emulsion which can cause the emulsion to break. When storing or transporting emulsion, you need to remember three important steps:
- BE POSITIVE – Know exactly what type of emulsion you are loading into your tank and what type of emulsion was in the tank previously, to ensure they are the same type of asphalt emulsion. Mixing measurable amounts of anionic and cationic emulsions will cause the asphalt particles to stick together forming a large mass of broken asphalt. This will take serious time and money to clean out of your equipment.
- STIRRED NOT SHAKEN – Pumping your asphalt emulsion imparts shear stress on the emulsion. Transporting the emulsion over long distances can adversely affect the quality of the emulsion. To minimize the damaging effects of pumping and travel, source emulsion as close to the job site as possible and when possible, always store the emulsion in a vertical tank. Talk to your emulsion supplier if your construction process will require the emulsion to be pumped more than 3 or 4 times.
- GET IT TOGETHER – Get to know the properties of your specific type of emulsion, especially its limitations. Some emulsions will chemically bond with certain types of aggregate much better than others. Some applications and equipment work best with rapid set emulsions. Some applications require medium or slow setting emulsions. Always use the recommended type of emulsion provided from the equipment manufacturer or your asphalt emulsion supplier and clearly label the tank.
Following these suggestions will help preserve the integrity of the asphalt emulsion being transported, but availability has been one of the most challenging obstacles to the pavement preservation industry. Depending on the specific region of your job site, asphalt emulsion may be limited to certain types, only in production during certain parts of the year, or too far away to transport to your location. Internationally, access to emulsion may be limited for the simple fact there are no emulsion plants in that geographic region. In order to better serve our customers, Bergkamp, Inc. has created a new enterprise, Bergkamp Bituminous Solutions.
To further Bergkamp’s vision to make roads better globally and provide our customers access to needed resources, Bergkamp Bituminous Solutions sells and supports a full range of emulsion mills and plants, polymer modified asphalt blending mills and plants, crumb rubber blending plants, laboratory plants, storage tanks, and mixers. Our new enterprise will allow us to introduce asphalt emulsion production into new markets and give our Bergkamp Pavement Preservation Solutions customers new resources.