APWA Winter Maintenance BRINE Sub-Committee FACT SHEET Spring 2016

What is salt brine? What is the difference between Anti-icing involves placing Salt brine is a solution of salt (typically anti-icing and deicing? a layer of brine on the sodium chloride) and water. It has Anti-icing is a proactive approach a freezing point lower than pure taken to decrease the likelihood of surface of the pavement water and, as such, is a useful tool snow and ice bonding to a pavement before a winter storm has in reducing the adhesion of snow surface. Additionally, anti-icing begun to prevent snow and ice to road surfaces. In addition can prevent frost from forming on to brine made with sodium chloride, pavement surfaces. Anti-icing involves and ice from freezing to some winter maintenance agencies placing a layer of brine on the surface the road. Deicing uses pre- also use brines made with calcium of the pavement before a winter chloride or magnesium chloride. storm has begun. This layer prevents wetted rock salt to break Nonetheless, these brines are solutions the snow and ice from freezing to (or the bond after snow has of salt and water, with a freezing icing onto) the road. The alternative— frozen to the road. point lower than the freezing point of which is called deicing—is to let the pure water. The freezing point of brine snow bond/freeze to the road, then is a function of the salt being used in apply pre-wetted rock salt to break the brine (sodium chloride, calcium the bond between the snow and the Anti-icing delivers the same chloride, or magnesium chloride) and pavement. level of service, but it uses the percentage by weight of that salt in the solution. Studies have shown that anti-icing one-quarter to one-fifth as will achieve the same level of service much salt as deicing. Why is salt brine important? on a road or highway using between Rock salt, or solid salt, is simply one-quarter and one-fifth the amount crystals of sodium chloride. Until it has of salt used in deicing. Typically, gone into solution—that is, until it anti-icing is performed using trucks Please direct media has formed brine—it will do nothing carrying tanks, which have pumps to questions to APWA to stop snow from freezing to the spray the brine onto the pavement Communications/Media pavement surface. Agencies that use surfaces. In many places lines or rock salt in their winter maintenance stripes of brine can be seen on a road Relations Manager Laura activities are doing so to create brine before a given event. Some people Bynum at 202-218-6736 or on the road surface. Therefore, brine call these safety stripes! Usually, brine is an integral and critical part of is applied at rates of between 30 and e-mail [email protected]. winter maintenance activities. 50 gallons per lane mile. using slurries of rock salt, which has as (without any additional dilution) at much as 50 gallons of brine per ton of about -6° F. Unless the road surface solid material. is extremely cold, the brine will not freeze to the road. Of course, as What about corrosion, isn’t brine it melts snow and ice, it becomes more corrosive than rock salt? more diluted and—unless additional As previously noted, if an agency is treatments are made or the road is using rock salt to its best advantage, cleared of snow and ice by plowing— it is employing brine. So, rock salt the road will refreeze eventually. But and brine are just two sides of the the short answer to this question is same coin. That said, yes, chlorides NO – the brine will not freeze on the Even in avalanche areas snow has been easily removed due to anti-icing. can cause corrosion in metals, and if road when it is applied. not treated properly this can cause Are all those liquids pure salt damage to vehicles and infrastructure. So, the brine won’t freeze, but brine? Some organic additives may have will it make the road slippery No, they are not. Increasingly, corrosion-resistant benefits. Certainly, some other way? agencies are blending brines to take laboratory studies show that some There have been concerns about this into account the particular storm of the organics reduce corrosion slippery issue since the early days conditions they expect to deal with. substantially. However, the best way of using brines in the US. Indeed, Blends often use by-products from a to reduce or avoid corrosion is to take AASHTO (the American Association variety of processes applied to natural the extra precaution of rinsing off any of State Highway and Transportation materials. Organics might include residue from the road salt or the brine Officials) considered this issue back by-products from cheese whey and the road salt has become. in the 1990s. They concluded there sugar beet or similar ingredients. The might be an issue of slipperiness purpose of organics is to increase the So, does putting down a liquid on with some brines, but it would only longevity of the brine on the pavement a cold road just freeze to the road? occur in very unusual circumstances. surface. Evidence has been presented Brine does have a lot of water in it. These circumstances could be avoided that organics may reduce corrosion For example, sodium chloride brine by simply not applying brine when of vehicles and infrastructure. Usually, is typically 23.3% sodium chloride pavement temperatures were warm, the concentration of organic additives when it is applied. That means that or when the air humidity fell within in brine ranges from 5 to 20 percent. it is 76.7% water. But, the salt is certain ranges. Provided those One typical mixture is 85% salt brine, in a solution in the water, and that restrictions are followed, brines do 5% calcium chloride brine, and 10% solution has a lower freezing point not cause slippery roads at all—rather organic. than pure water, as noted earlier. In they enhance road safety and mobility particular, when salt brine is applied at during winter weather and are a clear What is pre-wetting, and where a 23.3% concentration, it will freeze benefit to the traveling public. does it fit into all of this? As discussed above, rock salt does not reduce the freezing temperature of the pavement surface until it has created a brine. Rock salt is typically pre- wetted while it is being applied to the pavement surface. Rock salt can be pre-wetted in many ways. The general idea is to get the rock salt wet as it leaves the plow truck. This not only jump-starts the freezing temperature reduction process (and thus gets the salt “working” more quickly) but it also helps the rock salt stay on the road after it is spread. When rock salt is not pre-wet, as much as 30% may end up bouncing straight into the ditch or gutter. Pre-wetting is normally done at rates of around 8 -10 gallons of brine per ton of solid material, but some agencies are now working on Anti-icing roadways prior to an event in McHenry County, Illinois. (Photo courtesy of Mark DeVries)