Snow and Ice Control
The Limitations of Plain Rock Salt
For cost-effective deicing when temperatures are at or near freezing, you just can’t beat plain rock salt. But when the temperature drops below 20º-25ºF, salt’s effectiveness for ice control diminishes rapidly.
That’s because salt must first turn into a solution, or brine, to penetrate snow and ice. To form a brine, salt must come into direct contact with moisture. Naturally, the further temperatures drop below 32ºF, the less free liquid there is available to dissolve the salt in a reasonable amount of time.
As the temperature drops, so does the ability of untreated rock salt to melt a significant amount of ice in a given period of time. This limitation cannot be totally overcome by increasing application rates; although performance increases somewhat by creating more brine, the speed and temperature range limitations of plain rock salt persist.
The sluggishness of untreated salt at low temperatures can lead to other problems. While salt truck drivers wait for salt to begin working, traffic and wind scatter salt particles off the road. Also, drivers tend to re-spread soon after the first application because they don’t see much melting action. This dramatically increases the cost of material, labor and equipment. In addition, hazardous conditions last longer on main commuter routes. Therefore, the clearing of less-critical roads is delayed, and timeliness of service to suburban residents suffers.
This is not to say that rock salt is a poor solution to the problem of slippery, hazardous roadways. Quite the contrary. For decades, no other methods, chemical or mechanical, have proven superior until the pre-wetting concept was developed.
Advantages of Pre-Wetting Salt with Liquidow
Let’s examine how wetting salt with LIQUIDOW™ overcomes the limitations of rock salt.
- First, LIQUIDOW™ provides moisture which permits salt to become a brine quickly.
- Second, LIQUIDOW™ itself is a powerful deicer. Calcium chloride solutions easily dissolve snow and ice at low temperatures. Since it’s already a liquid, LIQUIDOW™ begins undercutting immediately on contact with the pavement, significantly enhancing the entire deicing process.
Thus, when wetted, salt works faster within its normal operating range. And wetted salt can work effectively at lower temperatures … all the way down to OºF. Tests by an independent research organization have shown that 100 lbs. of rock salt wetted with LIQUIDOW™ calcium chloride has the equivalent ice melting capacity of 110-125 lbs. of plain rock salt, depending on temperature and time elapsed after deicer application. This means rock salt wetted with LIQUIDOW™ calcium chloride is 10-25% more efficient at ice control, which can mean a significant savings in product used and dollars spent.
In addition to laboratory data, there’s the firsthand experience of many local governments. Surveys we’ve conducted indicate that most highway maintenance personnel believe the addition of LIQUIDOW™ enhances rock salt’s effectiveness considerably.
With a growing body of scientific data and case history reports supporting the performance of pre-wetting, the only question remaining is, “Can the added cost of pre-wetting with LIQUIDOW™ be offset with equal or greater savings?”
Justifying the Cost of Liquidow
To answer the cost question, it’s necessary to balance the anticipated investment in a salt-wetting program against the potential savings it can offer in the costs of both material and labor.
At typical addition rates of 8-15 gallons per ton of rock salt, a solution of LIQUIDOW™ calcium chloride will add about 10-15% to the cost of the salt, depending on your location relative to shipping points for salt and LIQUIDOW™.
But there’s another factor to consider: wetted salt is much less likely to “bounce and scatter” when spread. In fact, research conducted by the State of Michigan found that 30% of plain salt is lost when spread and another 24% ends up outside the center third of the road, where it is less effective.
A Public Technology report concluded that 30-50% less wetted salt could be spread for the same effectiveness because of reduced waste and improved performance. Indeed, just the 26% reduction in salt loss observed in the Michigan research would not only recapture the cost of LIQUIDOW™ but actually reduce costs as well.
Since wetted salt is effective at lower temperatures, however, you might spread it at temperatures when only abrasives would have been used before. If so, you might want to assume an even more conservative estimate of 10% less salt per road mile. Considering that abrasives are spread at much higher rates than salt and require additional time and cost for the spreading effort, reducing their use could also help to offset the small added cost of LIQUIDOW™.
Achieving bare pavement conditions with less deicer per road mile and fewer repeat-spreading and plowing runs means your road crews can treat more road miles with each truckload during each work shift. In short, as productivity increases, the need to pay overtime charges decreases.
Application Options: Affordable and Efficient
Three well-established application methods are being used separately or in combination to the advantage of many street and highway departments. This overview will help you determine the method(s) most appropriate for your specific situation.
Pre-Wetting: Truckload Application
The most common method in use today is some form of truckload application. In one version of such a system, the truck, loaded with dry salt, is parked beneath a time-controlled overhead spray bar system. By pushing a timer button, the driver activates a pump which sprays the salt with a 32% concentration of LIQUIDOW™ at an average rate of 12 gallons per ton.
Many variations on this system are possible. In one, liquid is applied to each bucketful of salt as it’s placed in the truck. In another, LIQUIDOW™ is sprayed on the salt as it travels up a conveyor belt to the truck.
Whichever variation is used, this method offers the advantage of a very modest investment in equipment. The basic components are a storage tank, a centrifugal pump, piping, a metering device, and wiring. Agencies can minimize these costs considerably by using components already on hand.
Pre-Wetting: Truck Mounted Application
Some agencies prefer a truck-mounted application system. These on-board wetting systems typically consist of a pump and hydraulic motor which direct the calcium chloride solution to a spray bar unit mounted above the spreader discharge chute. Tanks located alongside the hopper box store the LIQUIDOW™. The operator controls the liquid application from the truck cab.
Most on-board systems are designed by their owners. However, those in the market for new equipment can purchase spreader units with liquid application systems already installed.
Pre-Wetting: Stockpile Application
For those who wish to adopt a wetted salt program without equipment expenditures, a new application technique, stockpile wetting, offers an economical alternative.
Stockpile wetting requires no equipment at all. Rather, it is a service provided by authorized distributors.
Stockpile wetting is performed in the late fall or early winter when the temperature of salt stockpiles drops to approximately 30ºF. A heated solution of LIQUIDOW™ SW-42% Liquid Calcium Chloride is pumped into the pile at approximately 1-2 foot intervals using a special probe that penetrates into the pile. The application rate is 8 gallons of LIQUIDOW™ SW-42% per ton of salt. The heated LIQUIDOW™ flows through the stockpile, coating the salt with calcium chloride. As the solution is dispersed in the cool stockpile, its temperature drops rapidly. At 69ºF, crystallization of the LIQUIDOW™ SW-42% begins to occur. Deeper into the stockpile, crystal growth continues to advance until the stockpile is a mixture of calcium chloride crystals and rock salt. As long as the stockpile temperature remains below 69ºF, runoff of the solution should not be expected. Yet the wetted salt remains manageable even in the coldest weather. More important, you are ready to go with the deicer combination that improves your snow fighting program significantly.
It’s important to note several points about wetted stockpiles. Only LIQUIDOW™ SW-42% should be used for stockpile wetting. Weaker solutions will run through the stockpile. That’s because a 42% concentration of liquid calcium chloride crystallizes at 69ºF. As long as the wetted stockpile remains below this temperature, LIQUIDOW™ at 42% concentration added at the recommended rate of 8 gallons per ton of salt, will be completely crystallized in the stockpile. However, concentrations between 32% and 38% crystallize at much lower temperatures, and thus would partially run through the stockpile even at temperatures as low as 30ºF.
Also, all wetted stockpiles must be stored on impervious asphalt or concrete slabs, and covered to prevent dilution and runoff caused by rain or snow. Users are also urged to follow the recommendations for salt storage outlined in the “Sensible Salting Program” suggested by the Salt Institute, with guidelines for salt storage and handling, equipment management, and employee training.
Treating Abrasives with Liquidow – Why Treat Abrasives at all?
During many winter storm conditions, abrasives become one of the few effective materials for keeping roads safe for travel. It follows that they must be quickly available at all times to ease these severe conditions when plowing cannot keep pace and the use of chemical deicers alone is not practical.
The key to fast response with abrasives is keeping them easy to handle. Unfortunately, abrasives tend to freeze and become most difficult to mix, store and handle during the extreme conditions they are intended to remedy. Mixing sand, cinders and aggregates with chemical deicers prevents moisture in the abrasive mix from freezing so these materials remain loose, manageable and instantly available when ice control is needed. Road crews are able to load quickly and easily from free-flowing stockpiles. The equipment works easily and efficiently without clogging or added strain.
Why Calcium Chloride?
Calcium chloride is the preferred chemical deicer for treatment of abrasives for one simple reason; it gives protection from freezing at much lower temperatures than any other. When either the dry or liquid forms of calcium chloride are applied as recommended, they can be expected to perform at temperatures down to -20ºF , and lower, depending on the type of abrasive and its water content. Calcium chloride also melts from 12%-56% more ice than salt and is able to begin melting action much faster at lower temperatures. Sodium chloride (rock salt) cannot give protection at these very low temperatures, and it creates difficult handling and mixing problems.
Besides keeping abrasives quickly and easily available, calcium chloride also makes these materials more effective in two related ways.
First, because the abrasive particles are coated with the most potent chemical deicer available, they imbed into hard-packed snow and ice immediately. The abrasive becomes the instant traction aid it’s meant to be. Under many conditions, the treated particles even bore through snow and ice to create a “honeycomb” effect. This makes blading to bare pavement possible more quickly.
Second, since each particle imbeds itself far more quickly, there’s less chance of material being lost due to “whipping” by passing traffic. The net effect is a reduction of waste during winter and less unneeded cleanup in spring. Total dollar savings can be dramatic as a direct result.