January 2002

Anti icers

Anti icers: Driving toward clearer roads

These chemicals will change the way you think about snow removal.

By Wilfrid Nixon, University of Iowa

Traditionally, much of your snow-removal work involves clearing snow and ice from roads and parking lots after a snow event. While that’s a large part of a winter-management plan, there’s something else to consider, something that could make an easier job of your normal snow and ice removal: anti-icers. By integrating them into your overall snow-removal strategy, you can get the jump on the next snow event by approaching it proactively.

Anti-icing has been defined as "the snow and ice control practice of preventing the formation or development of bonded snow and ice by timely applications of a chemical freezing-point depressant." Essentially, the idea behind anti-icers involves timing: putting chemicals on the road surface prior to snowfall. Generally, the chemicals you will use in an anti-icing program are liquid chemicals, although in certain circumstances, you may also use solid chemicals that have been pre-wet at the spinner.

For more information on anti-icers, see the Federal Highway Administration's (FHWA) Manual of Practice for an Effective Anti-Icing Program: A Guide for Highway Winter Maintenance Personnel, available electronically at: http://www.fhwa.dot.gov/reports/mopeap/eapcov.htm.

Taking a proactive approach

Experience suggests that anti-icing is an extremely effective technique for providing high levels of service during winter storms and for providing that level of service with reduced costs and reduced quantities of chemicals as compared with more traditional methods. If you need some specific confirmation of the effectiveness of anti-icing, an NCHRP (National Cooperative Highway Research Project) study (number 20-7/117) has been published with a detailed cost-benefit study for anti-icing. A specific case study is also available, based on the maintenance of U.S. Highway 12 in Idaho. On this stretch of road, several years of usage of anti-icing has produced an 83 percent reduction in accidents, a reduction of 83 percent in abrasives used and a 62 percent reduction in labor hours. It’s hard to argue with those numbers!

To read the full NCHRP report, go to the online publication at http://www.sicop.net/NCHRP20-7(117).pdf. The Idaho case study is available online at http://www.sicop.net/US-12%20Anti%20Icing%20Success.pdf.

So, what do you do if you want to implement anti-icing in your area of responsibility? You need to implement four areas of change.

Special equipment. Your equipment must include chemical storage and chemical delivery systems. You may also decide to mix the anti-icing liquids yourself, in which case you’ll need a production facility. Chemical storage requires a sufficient number of large storage tanks (capable of holding thousands of gallons of liquids), along with pumps to deliver the liquid onto the trucks. Your trucks will need tanks and spray equipment.

There are a number of sources that will provide information on the equipment you will need. The Iowa Department of Transportation (DOT) provides its anti-icing equipment guide on the Web at http://www.dot.state.ia.us/maintenance/manuals/equip/index.htm. In addition, there are specifications for various anti-icing pieces of equipment used by Idaho DOT at http://www.sicop.net/documents.htm.

· New operational methods. The way you operate your snow and ice control business will have to change if you are going to use anti-icing. Specifically, because anti-icing is proactive, you need to be proactive as well, working before a storm begins and putting chemicals down on the road surface to prevent formation of a bond between the snow and ice and the pavement. The key factor in making this change is getting good forecasts for the road surface condition, rather than for just the "weather." The temperature of the road surface can be, and often is, a couple of degrees different from the air temperature, and that difference is more than enough to make life very awkward indeed for you.

The classic way of getting information about the road temperature is through an RWIS (Road Weather Information Station) system. However, these systems can be very expensive (between $25,000 and $75,000 per site), so unless you have one already, your best bet may be to obtain data from somebody else’s system. Many state transportation departments have extensive RWIS systems in place, and provide temperature information on the Web. In addition to just using the Web data, you might also be able to access your state DOT pavement temperature forecasts if you ask for them. (The worst that could happen is that they say no, right?) However you get the information, knowing your pavement temperature and whether it is increasing or decreasing will be critical to your success.

As an example, you can view the temperature across Iowa's road network at: http://www.weatherview.dot.state.ia.us/.

¸ New management techniques. You also have to train your crews in this new way of doing business. They may be skeptical about putting chemicals on the road before it snows. They may not feel comfortable using fewer abrasives than they have historically. If they aren’t trained appropriately, the switch to anti-icing will not be a success. The FHWA Manual (see above) has lots of useful ideas on how best to do this training.

¹ Selecting anti-icers. How do you go about selecting the best chemical for your needs, if you are making the switch to anti-icing? The first step toward choosing a chemical is considering the various factors that determine how well a given chemical will meet your needs. However, three key ones are worthy of special attention.

q First, you have to figure whether a given chemical will function effectively in your climate. This is a function of the temperatures that you normally see in wintertime.

q Second, you might be concerned about how corrosive the chemical is. If you have infrastructure that is particularly vulnerable to corrosion, or that you wish to take special pains to protect (a new bridge, for example), then the corrosion factor is an important one.

q A third factor is the environmental impact of the chemicals you will use. All the chemicals eventually end up off the road. Depending on your year-round climate (do you get a lot of rain that will dilute and flush away chemicals, or are you fairly arid?) and the sensitivity of your environment (do you live in a fishing paradise?), this too can be a critical factor. We’ll review each of these factors below.

While these factors are some of the most important ones, you should also consider others, such as the completeness of documentation, the consistency of the product from batch to batch, the stability of the product and what it takes to handle the product safely and effectively. Whatever chemical you decide to use, you need complete documentation and a quality assurance program in place. You need to be certain that what you put on the road will do the job you expect it to do, each and every time you use it. You also need to be sure that the product you choose will not change substantially from batch to batch. Simple checks on viscosity and specific gravity can serve as indicators of any problems, but again, this is one of those things you just have to know. Also, some of the new products on the market have significant agricultural components in them (perhaps derived from corn, or other crops). These things can change over time (for example, they might start growing mold), so be aware of whether this is a concern for your choice of product. And if you get a particularly thick or heavy product, it may "stick" very well to the road but it could be difficult (to be generous) to pump it through your delivery system. Also, the tanks you store it in may require some form of reinforcement to hold it safely.

There are a number of factors considered in detail for selecting an anti-icer in the "Guide for Selecting Anti-Icing Chemicals" which is available on the Web at: http://www.anti-ice-guide.com/.


Temperature is likely to be your first concern. Often, but not always, producers will talk about a eutectic temperature (see diagram, above). The way any deicing or anti-icing chemical works is by forming an "alloy" with water to depress the freezing point. The diagram shows this, in what is termed a phase diagram (or sometimes a eutectic curve). The lowest temperature the water-chemical mixture can go to before it freezes is termed the eutectic temperature or the eutectic point. However, operationally it’s not very helpful. For example, the eutectic point for a salt (sodium chloride) water mix is about –6º F. But if you apply salt at that temperature, it will do you no good at all. While it might (eventually) melt some ice, it won’t melt much. Typically, salt should not be used below about 15º F at best, and in general, 20º F would be a better cut off point.

Temperature performance has to be considered as more than just one number off a graph, and I’d suggest you compare chemicals as follows. First, find out what concentration of mixture the supplier recommends you use (for a salt brine this would be close to the eutectic mixture, as this is the most potent possible mixture). Then find out at what temperatures the mixture will start to freeze (that’s the "freezing line" in the diagram), as well as the freezing point for a mixture that is diluted to half strength and then for another mixture diluted to quarter strength. For salt brine, those temperatures would be 18º F and 26º F respectively. You should choose a chemical that has a quarter-point temperature (the freezing point of the quarter-strength liquid) that is below a typical mid-storm temperature for your region. Also, the chemical should have a half-point temperature (the freezing point of the half strength liquid) that is below about 90 percent of your storms. And if the supplier can’t give you that information (preferably measured by an independent agency), then you should no longer consider the product for your needs.


In terms of corrosion, tests are a little more difficult. A group of states (and one Canadian province) has formed a loose organization called the Pacific Northwest Snowfighters, and have developed a specification for corrosion resistance. If corrosion is a concern for you, then any product you consider should have been tested according to the PNS protocol.

Further details on corrosion are available at the PNS Web site: http://www.wsdot.wa.gov/fossc/maint/pns/.

Environmental impact

Measurement of environmental impact of deicers is less well developed. If environmental concerns loom large for you, then you need information on the BOD and COD (Biological Oxygen Demand and Chemical Oxygen Demand) for the products you are considering. You might also consider some sort of toxicity testing and, if stream water quality is a major concern, you probably need to have a measure of the nitrogen content done too (the Kjeldahl Method would be the applicable standard here). Again, manufacturers with good products can help you with these matters.

Liquid chemicals

The basic liquid chemicals at present would be liquid brines of sodium chloride, calcium chloride and magnesium chloride. Added to these would be two acetate-based deicers: calcium magnesium acetate and potassium acetate. Other new chemicals are in development but haven’t made it to the market to any great degree—yet! Often, suppliers will add things to these basic brines to change certain performance factors. They may add an element to reduce corrosion (called a corrosion inhibitor) or to mitigate environmental effects or even to improve temperature performance. Sometimes what they add is developed as a by-product of some other process (agricultural by-products are becoming more and more common in the anti-icing market these days). However, whatever they add, you need to be sure that the final product will do what you want it to do—and that means you should request appropriate test data from the suppliers.


Finally, you’ll notice I’ve said nothing in all of this about price. That’s quite deliberate. Obviously, price is important (and perhaps even critical) in making your choice. However, paying less to get a product that won’t do what you need it to is a false economy. First, find the products that can do what you need them to; then, rank them according to price (and availability, delivery, service and other factors).

Anti-icing is an extremely effective approach for winter maintenance. We now have substantial experience with it in North America, and it’s well worth taking a look to see if it can help you in your winter maintenance. Good luck, and keep warm!

Wilfrid Nixon is professor of engineering for the University of Iowa (Iowa City, Iowa).


Turning skid steers into snow movers

Don't park your skid-steer loader in a shed until next spring. Turn it into a winter machine by adding the right work tools.

By Sherrie Baker, Caterpillar, Inc.

Each summer, landscape and maintenance crews routinely make the skid-steer loader the busiest piece of equipment on the job. Skid-steer loader buckets haul, brooms sweep and blades level from the break of the first bud to the fall of the last leaf.

Yet winter is another chance for the machine to prove its versatility. In fact, snow removal is one of the skid-steer loader’s best applications. The machine is small enough to clear sidewalks, yet big—and powerful—enough to handle entire parking lots. It can fit into tight spaces and perform productively in the open.

Getting attached

The machine’s performance is only part of the equation. Just as crucial are the work tools, which make the skid-steer loader even more versatile. By changing the work tools, the skid-steer loader can handle any snowfall, whether it’s a dusting or more than a foot.

Because work tools can be changed quickly, and with ease, the skid-steer loader is quickly becoming the snow-removal tool of choice for many crews charged with clearing parking lots and sidewalks at retail centers, industrial parks, schools and universities and just about anywhere else snow removal is needed. If used properly, the work tools can make a skid-steer loader perform as if it were custom-built for a particular snowfall.

Here is a look at some of the most common work tools that help the skid-steer loader flourish in a variety of winter conditions.

 Snow Blowers. These work tools do the job in the hard-to-reach places. Many snow blowers operate on standard-flow hydraulics and are best suited for removing snow from streets, parking lots, driveways and sidewalks.

When shopping for a blower, make sure the impeller is engineered to balance power and torque. This maximizes capacity and throwing distance and helps prevent plugging—as do chutes featuring non-metallic liners. Attachments are available in a variety of widths, cutting heights and throwing distances. Rotational spouts ensure the snow goes where you want it to.

 Brooms. Many landscaping and maintenance crews use brooms to remove dirt, rock and other debris at sites. But the brooms also can do the job when a light snow falls. In fact, they’re a great fit for streets, driveways and sidewalks. Angle brooms use a windrow action to move snow ahead and to the side of the broom. Pickup brooms sweep and deposit snow into an integrated hopper bucket for removal and dumping at another location. This is necessary when earlier snowfalls make it difficult to sweep the material to the side.

 Angle Blades / Snow Blades. These come in varying sizes, typically starting at about 72 inches. The best blades offer at least two types of optional bolt on edges to best fit your application needs—metallic and non-metallic. Metallic edges are typically used through out the year for leveling and grading dirt. However, non-metallic edges may be preferred when needing to remove snow without damaging the surface below. Also crucial during snow removal are high-visibility edge markers that indicate blade width and orientation. The most versatile angle blades offer the capability to operate in two ways: with blade locked for aggressive dozing in dirt applications or with the blade spring-loaded trip engaged when pushing snow.

 Light Material Buckets. While the bucket is built for a light application, it also should be able to handle a large payload. This is accomplished through long floor length and tall back height. Specifically, a 72-inch bucket should have a capacity of just under a yard. Extended-lift skid-steer loaders easily are able to lift and dump snow over the edge of a transfer truck.

 Multi-Purpose Buckets. These work tools can be used to remove snow in the winter and for digging, dozing, clamping, back-dragging, grading and leveling during the rest of the year. Make sure buckets have corrosion-resistant materials, often accomplished through plated hinge and cylinder pins. Multi-purpose buckets have a range of capacities. Look for one that is big enough to be productive but still able to fit into any tight spaces the job might require. The multi-purpose bucket, like the light material bucket, also can be attached to skid-steer loaders with extended reach.

When searching for work tools, it’s crucial to keep winter in mind—and the corrosion it can cause. It’s also important to remember that the proper work tool can boost productivity and reduce the time it takes workers to remove snow. Owning a skid-steer loader is a step in the right direction when aiming for productive snow removal. Purchasing or renting the proper attachment completes the equation.

Sherrie Baker is senior marketing project engineer for Caterpillar Inc. (Peoria, Ill.).







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