SAFE WINTER ROADS START WITH CALCIUM CHLORIDE
An Introduction to Calcium Chloride for Deicing
Clearing snow and ice can be a continuous battle. Often, rock salt (sodium chloride), sand and abrasives are the first salvo fired in battling a winter storm. But dropping temperatures can cause ice or packed snow to form – and as the temperature drops, so does the deicer’s melting ability.
Winter Road Uses
Calcium chloride is many things to many people. In warm weather it controls dust, helps stabilize road bases and assists in asphalt recycling. In winter maintenance programs it:
Calcium chloride, in 32% solution or 83-87% flake form, can enhance rock salt, sand and abrasives’ effectiveness to achieve safer, bare pavement, at all temperatures. Studies show that in 85% of applications calcium chloride/rock salt mixtures achieve bare pavement faster than rock salt alone at temperatures near 30°F (-1°C), which helps to clear roads, easing traffic and reducing accidents.
Liquid calcium chloride can freeze-resist and thaw frozen stockpiles. By spraying calcium chloride on rock salt, sand, abrasive, limestone, woodchip, coal, ore and mineral stockpiles, they are kept free-flowing in winter. Calcium chloride provides long-lasting protection after stockpiles are built, or returns a frozen-solid mass to its original condition.
Getting to Know Calcium Chloride
Calcium chloride, as an additive for deicing, offers many advantages:
- Hygroscopic – attracts moisture to form brine more rapidly than other products in low humidity winter environments.
- Exothermic – releases heat as it melts, to speed rock salt’s melting ability.
- Fast acting - begins to dissolve immediately upon application to break the bond between pavement and ice. At 25°F (-4°C), rock salt takes a full 19 minutes to embed in ice and hard-packed snow. But wetted with a 32% calcium chloride solution, rock salt immediately digs in and holds a close pattern on winter roads.
- Long-lasting – the brine remains active for prolonged periods of time, to prevent ice from bonding to the highway.
- Low eutectic point - melts at a much lower temperature than rock salt: controlled studies prove its effectiveness down to -25°F (-32°C).
- Minimizes environmental impact - melts ice and snow faster and longer so less deicers are required. This reduces the amount of sodium chloride introduced into the environment, both through application on the roads and leaching into the ground when stored. Plus, it is five-to-ten times less harmful to vegetation than rock salt.
The Peters Chemical Advantage
Occidental Chemical Corporation manufactures calcium chloride from aqueous brine that is extracted from natural underground deposits. This calcium chloriderich brine is concentrated by water evaporation and purified. The purified brine is either sold in solution form or used to feed dry calcium chloride manufacturing units that produce concentrated solid product in flake or pellet form.
Compare this process with calcium chloride manufactured by solution mining from geological deposits. The calcium chloride produced from this brine may have high levels of environmentally problematic impurities, such as sodium, strontium, barium, bromine and magnesium.
DEICING WITH CALCIUM CHLORIDE
Rock salt can be added to water to reduce its freezing point. To be effective at lower temperatures, however, rock salt requires heat and moisture, two things often lacking on cold, dry winter days. In addition, even when the melting action has begun, rock salt absorbs heat during the process. That’s why the melting action of rock salt slows substantially at lower temperatures, especially when approaching 25°F (-4°C). Calcium chloride, on the other hand, attracts moisture and produces brine as it melts, releasing heat during the process. Rock salt’s ice and snow melting performance can be enhanced with either liquid or flake calcium chloride as a:
- Pre-mix, where flake calcium chloride is applied in a mix with rock salt, or…
- Pre-wet, where liquid calcium chloride is either added to rock salt and or abrasives by an overhead spray bar prior to application or applied as the materials leave the spreader using a truck-mounted system.
Using either calcium chloride pre-mix or pre-wet can:
- Decrease labor costs by up to 20% and reduce wear and tear on equipment by eliminating second and third application runs, especially at temperatures below 25°F (-4°C). The brine formed by calcium chloride remains active for prolonged periods to prevent ice from bonding to the highway.
- Reduce the amount of material from 30-50%. Calcium chloride helps materials embed in ice and snow, so less material is lost to spreader bounce and traffic scattering. Reports indicate that rock salt has been spread at rates of 500lbs. (226Kg.) per lane mile, whereas calcium chloride used with rock salt allows rates as low as 250 lbs. (113Kg.) per lane mile.
- Minimize spring and summer clean-up costs by cutting down on the amount of sand and abrasives thrown off onto the shoulders, especially on hills.
- Increase the effective melting temperature – down to -25°F ( -32°C), much lower than rock salt alone.
- Melt the ice and snow faster to make plowing easier.
Experienced User Suggestions for Calcium Chloride
Calcium chloride application rates and techniques vary greatly depending on snow and ice accumulation and temperature. Some typical methods and tips are shown below. Optimal application rates fall in the range of approximately 200lbs. (91Kg.) to 300 lbs. (136Kg.) per lane mile.
Business districts/residential areas
High traffic volume and mild temperature ranges in downtown areas allow good road clearing results with light pre-mix/pre-wet applications.
- Where traffic is heavy and fast, spread a fairly wide windrow down the center of the road. Traffic will then work the material toward the edges without pushing it off the shoulder.
- In residential areas, where traffic is slower, spread material in a narrow windrow down the center of the pavement, and flare out coverage at stop lights.
Divided expressways require wider-spread windrows, because their one-way traffic cannot spread pre-mix/pre-wet laden snow to the outside.
- During peak traffic hours, treat urban expressways with heavier windrow applications — heavy traffic makes reapplication difficult as temperatures drop.
- Protect passing lanes and on/off ramps with heavier applications. Also, spread material to the high sides of curves so it can work downward.
Controlling snow and ice on dirt roads demands a different approach than on paved roads because their surface temperatures are lower. It is recommended that only calcium chloride be used as salt will recrystallize and cause the road surface to become tacky.
- Spread the material down the center in a narrow windrow to reveal the center line as quickly as possible on country roads. This enables drivers to see the center of the road and stay in the correct lane.
PETERS CHEMICAL COMPANY OFFERS OPTIONS TO COVER YOUR DEICING NEEDS
Pre-wetting Winter Maintenance Materials with Liquid Calcium Chloride
Coating rock salt, sand and abrasives with 32% liquid calcium chloride can strengthen your winter road maintenance programs. Pre-wetting winter maintenance materials offers the following advantages:
- Cost-effective flexibility for treating material on truck-mounted systems when the weather or specific road sites need it.
- Decreases amount of deicer lost to “bounce and scatter” by helping material immediately embed on winter roads.
How to Prepare Pre-wetted Rock salt
The techniques for pre-wetting materials with calcium chloride vary only slightly from conventional rock salt and abrasive preparation
- Overhead Spray Systems
Rock salt, sand and abrasives can be loaded into the spreader truck and positioned beneath an overhead spray system. The calcium chloride solution is then sprayed over the materials using a timer-controlled system to control application rates.
- Truck-Mounted Systems
Spreader trucks, equipped with calcium chloride truck-mounted systems, are loaded with material. During application, the material is wetted with calcium chloride solution as it falls into the spinner. The rate of application can be adjusted by the operator to accommodate varying temperature, snow and ice conditions, and the intensity and duration of a storm.
Pre-mixing Winter Maintenance Materials with Flake Calcium Chloride
Pre-mix (83-87% flake calcium chloride mixed with rock salt and/or abrasives prior to application) provides extra strength to your winter road maintenance program versus pre-wet materials. It gives additional deicing performance at low temperatures and in harsh climates. It offers an alternative to pre-wetting for those highway departments which stockpile their materials. Pre-mixing winter maintenance materials offers the following advantages:
- Pre-mix is the most effective deicer available.
- Stockpiles can be prepared months in advance and stored for future use.
- Hopper and tailgate spreaders can be loaded quickly.
- Offers an economical and more effective alternative to stockpile injection.
How to Prepare Pre-mix
There are several easy ways to mix flake calcium chloride with winter road materials:
- Combine calcium chloride with rock salt, sand and/or abrasives manually.
- Combine the desired amounts of each flake calcium chloride and rock salt, sand and/or abrasives from two separate piles with a front-end loader.
- Use a combination conveyer belt and hopper to mix the materials.
- Spread a bucket-load of calcium chloride over the front of a stockpile before loading in tailgate spreaders.
- Spread several bags of calcium chloride over hopper.
- The best method when the salt is damp — load the calcium chloride and materials by layers into hopper and allow them to mix as they are spread on the roadway.
How Calcium Chloride and Rock Salt Compare
|Calcium Chloride||Rock Salt|
|Releases heat||Absorbs heat|
|Attracts moisture||Requires moisture|
|Produces Brine||Brine needed to start melting action of salt|
|Fast melting action|
Standard rock salt storage buildings are one of the most cost-effective storage facilities for bulk flake calcium chloride or pre-mix. Flake calcium chloride may be stored in buildings, protected cribs or overhead steel bins. Often, existing facilities can be converted for effective storage, providing there is adequate drainage. Flooring is essential, and should consist of a bituminous pad over a crushed aggregate base. All material must be covered with a moisture-tight tarpaulin to restrict the flow of moisture-containing air. Good maintenance procedures, such as covering the pile after use, will ensure free-flowing material.
An alternative to building storage is stockpile storage of flake calcium chloride or pre-mix. The stockpile must be grounded on a base that is built up in the center, allowing drainage on all sides. A bituminous pad cover a crushed aggregate base will protect the pile from the ground up. A moisture-tight tarpaulin covering, weighted down with sand bags or tires, is essential.
Liquid calcium chloride should be stored in all-welded steel, fiberglass, or plastic storage tanks. Piping, valves and pumps should also be selected from these materials of construction.
Under some circumstances, storing bulk ice-melting chemicals (including rock salt) may pose environmental concerns. Consult the appropriate regulatory authorities before constructing or modifying storage facilities.