CALCIUM CHLORIDE – The essential element for better roads
ON THE ROAD: THE USES OF CALCIUM CHLORIDE
There are many ways in which calcium chloride can help your road.
Calcium chloride is one of the most effective dust control agents in the industry.
A stable base requires maximum density, and moisture control is the key to density. Calcium chloride is an economical, dependable additive for obtaining optimum moisture during construction.
Full depth reclamation
When recycling roads through full depth reclamation, calcium chloride can provide a stabilized base that can withstand traffic even before the wearing surface is applied.
Whether you’re stabilizing a road base or reclaiming a road, calcium chloride helps prevent costly maintenance problems. With a strong, structurally-uniform base that results from using calcium chloride, your road will be more resistant to problems like frost heave, uneven settlement, potholes and ruts…. So it will last longer and require less maintenance.
Each season brings new challenges to your road maintenance program. You can meet these challenges; improve the quality of your roads, and lower maintenance costs by using calcium chloride as part of your ongoing highway maintenance strategy.
ROAD-RESCUING PROPERTIES OF CALCIUM CHLORIDE
- Hygroscopic: calcium chloride absorbs moisture from air and surroundings.
- Deliquescent: calcium chloride dissolves in the moisture and forms a clear solution that is extremely resistant to evaporation.
- High surface tension: calcium chloride lubricates the aggregate, improving the interlocking action.
HOW CALCIUM CHLORIDE SAVES ROADS AND MONEY
- Improved dust control: Calcium chloride retains moisture for prolonged periods. This unique property helps to hold down dust and stabilize unpaved road surfaces, creating smooth-riding roads that last.
- Reduced routine maintenance costs:
Since calcium chloride treated roads need less maintenance than roads treated with other materials, you can save on labor, equipment and fuel costs. By maximizing compaction, calcium chloride also provides a longer-lasting road.
- Reduce gravel replacement costs: Up to 80% of the cost of aggregate replacement can be saved when calcium chloride is properly applied.
- Reduced construction costs: Because calcium chloride speeds compaction, less rolling is required to achieve greater density, which translates into greater labor savings. When used with full depth reclamation, calcium chloride can help reduce road reconstruction costs by as much as 50%.
CALCIUM CHLORIDE IN DUST CONTROL
Dust is a public nuisance on unpaved roads, and can affect visibility to such a degree that driving becomes hazardous. Uncontrolled dust can also lead to a break-down of the road itself.
Calcium chloride is highly effective as a dust control agent, because it resists evaporation. As a result, calcium chloride keeps dust down longer than other dust control agents.
CONTROLLING DUST FOR LESS
Calcium chloride is a cost-effective-and highly effective-agent for dust control, providing savings of up to 50%. Calcium chloride also:
- Reduces grading costs by as much as 50%
- Reduces replacement cost of gravel and other materials by up to 80%
- Reduces labor costs
- Poses minimal threat to the environment, because it resists leaching. In fact, calcium chloride is used in food processing, fertilizers and as a nutrient in some applications.
APPLYING CALCIUM CHLORIDE FOR DUST CONTROL
- Blade and shape the surface to allow water to drain off properly.
- Apply a 35% solution of calcium chloride using a tank truck with a rear-mounted distribution bar that spreads the liquid evenly over the road.
- For proper road maintenance, apply a second time later in the summer.
APPLICATION TIPS FOR DUST CONTROL
- Calcium chloride works best when applied just before roads become dry and dusty, because it can then retain moisture already present in the road.
- Apply calcium chloride immediately after spring shaping, before the road has dried from the spring rains.
- Although liquid calcium chloride makes unpaved roads hard, it can make paved roads slick. Distributor trucks should reduce speed about 100 feet (30 meters) before paved areas and use extreme caution treating the remaining unpaved area.
CALCIUM CHLORIDE LEAVES OTHER AGENTS IN THE DUST
- Water can’t resist evaporation like calcium chloride; that’s why water can only delay dust instead of control it. Once the water evaporates, you will have to water the road again. And frequent road watering adds up to greater operating costs.
- Oil is messy, chokes roadside foliage, and causes a crusty, crumbling road surface when it dries. Oil also costs at least three times as much as calcium chloride.
- Oil emulsions are less expensive than oil alone, but as the water evaporates, the problems of the oil messiness and a crumbling surface remain.
- Lignosulfonate, a by-product of paper mills, is less expensive than calcium chloride, but it lasts a fraction of the time. Frequent reapplication is necessary due to wash-out caused by rain-which translates into extra costs and maintenance trips.
THE IMPORTANCE OF BASE STABILIZATION
To the public, the dust clouds trailing cars and trucks on unpaved roads are a nuisance, even a driving hazard. To those who maintain these roads, the fines leaving the road as a dust threaten the road’s very existence.
Fine particles in a road fill the spaces between coarser aggregates which bind them into a compact, dense surface. When the fines are lost, traffic will break down the road surface, scattering the aggregate and causing ruts, washboard, and other hazardous problems. One study estimates that a single car travelling on an untreated road once a day for a year would throw off a ton of gravel per mile. Such unchecked deterioration leads to costly road rebuilds and higher road maintenance costs…not to mention complaints by local citizens.
Proper application of calcium chloride will stop the damage before it starts by maintaining a clean, solid, smooth-riding surface.
CALCIUM CHLORIDE KEEPS IT TOGETHER…
A road is only as strong and durable as its base… and the integrity of the road base depends on proper interlocking of aggregate.
Calcium chloride absorbs moisture from the air to form a clear liquid. This liquid is extremely resistant to evaporation and is attracted to negatively-charged soil particles (clay), which decreases leaching. Because it resists evaporation, calcium chloride maintains optimal moisture levels (between 7-8%) during compaction to attain a high density.
The calcium chloride solution penetrates the road’s material, coating tiny particles of dust and gravel, binding them together. This binding action stabilizes the unpaved road, keeping it dense and compacted. Aggregate particles also interlock faster, speeding the compaction of the base. That means calcium chloride treated road bases reach greater density with fewer rollings than bases using only plain water — which translates into labor savings. In fact, the cost of calcium chloride is often completely offset by the savings it provides in construction costs.
The calcium chloride solution moves deeper into the base during wet weather; during dry spells it rises towards the surface through capillary action to keep the surface moist. In this manner, moisture is maintained in the road to minimize the loss of fines. As a result, the road remains dense and compact under almost any level of traffic — even on the hottest, driest days.
Calcium chloride is a cost-effective alternate to paving, providing savings of up to 50%. Calcium chloride also:
- Reduces replacement cost of gravel and other materials by up to 80%
- Reduces compaction effort on loose granular surfaces by 60%
- Reduces labor costs
- Enables emergency and local traffic to use roads right after application, because it firms up almost immediately.
APPLYING CALCIUM CHLORIDE FOR BASE STABILIZATION
Use the following steps to stabilize the unpaved road:
- Scarify the existing granular surface.
- Select and add aggregate as needed.
- Add 75% calcium chloride by weight of aggregate. Spray a 35% solution of liquid calcium chloride evenly over the road.
- Mix all materials.
- Create a 4% slope on either side of the crown.
- Compact the surface uniformly.
- Add 0.25% calcium chloride by weight of aggregate to seal the surface.
APPLICATION TIPS FOR BASE STABILIZATION
- Make sure roads have proper drainage so that water will not undermine the roads.
- Spray within a couple of days after grading to reduce the time that the roads are vulnerable to traffic.
- Spraying the liquid under pressure helps ensure the application is more uniform.
- Avoid very wet weather when spraying. If a heavy or steady rainfall occurs just after spraying a road, the runoff will take some of the calcium solution with it, especially on steep grades.
CALCIUM CHLORIDE STANDS UP TO OTHERS
- Water can’t control the road’s moisture content because it can’t resist evaporation. Calcium chloride is resistant to evaporation, so it continues to attract and retain moisture which improves compaction. So calcium chloride can help reduce your maintenance trips, grading, rework, and man-hours. It can also reduce equipment, fuel, and repair costs. Water only works as long as long as it’s around. As soon as water evaporates, so do your savings!
- Oil does not bind aggregate as well as calcium chloride, since it merely forms a thin crust on top of the aggregate. And when this crust breaks off during grading, potholes appear.
- Oil emulsions have the same effect as oil alone: they produce crumbly, crusty roads.
- Lignosulfonate requires more frequent applications than calcium chloride-which increases your labor and maintenance costs.
RECYCLING ROADS THROUGH FULL-DEPTH RECLAMATION
Full-depth reclamation is a straightforward process that uses pulverizing equipment to grind a road’s existing asphalt and gravel base into a uniform aggregate composition. Liquid calcium chloride is then blended in, resulting in a stabilized base course.
CALCIUM CHLORIDE MAKES RECLAIMED ROADS BETTER…
Studies show that roads reclaimed with liquid calcium chloride can withstand stress and shock, and distribute load better than roads reclaimed without calcium chloride. Liquid calcium chloride lubricates the fines and allows them to adhere to each other and to the aggregate. So calcium chloride makes optimum compaction easy to achieve, which in turn keeps the road dense and compact under almost any level of traffic.
Because calcium chloride’s fast firming-up action helps keep aggregates in place, traffic can usually continue using the roadway during construction. This fast, dependable action also makes stage construction possible. And because calcium chloride has a low freezing point, the full depth reclamation season can be extended from just after frost into late November.
…AT A BETTER PRICE
Using liquid calcium chloride for full depth reclamation can help you add structural value and cost savings to your own operations:
- Aggregate treated with calcium chloride reaches greater density and compaction with less rolling, thereby speeding the work. In addition, emergency and local traffic can still use the roadway during construction and before asphalt is applied because liquid calcium chloride sets up almost immediately.
- Calcium chloride extends road life and reduces the amount of patching and other maintenance needed. Many officials anticipate an average life expectancy of 15 years or more for roads reclaimed with calcium chloride, as opposed to 5-10 years for roads without calcium chloride.
- Full depth reclamation recycles existing materials, so disposal concerns (and costs) are eliminated, while natural resources and energy are preserved. Calcium chloride also reduces the threat to the environment.
- Because the reclamation process is accomplished in place, the heating, mixing and hauling costs of conventional reconstruction techniques can be eliminated.
- Calcium chloride reduces the effects of frost action by 50 to 60%. It has an antifreeze effect which lowers the freezing point of the moisture in the base.
HOW TO RECLAIM ROADS WITH CALCIUM CHLORIDE
Full depth reclamation with calcium chloride only takes six steps:
- Pulverize asphalt, mixing it with a predetermined amount of underlying base materials. The old surface becomes part of the new road base.
- Apply calcium chloride at the rate of 0.75 gallons per sq. yd. (3.9 liters per sq. meter).
- Pulverize a second time to thoroughly mix asphalt, base material and calcium chloride.
- Grade the materials to establish the desired surface profile.
- Roll the surface to consolidate the materials. Calcium chloride lubricates the materials, aiding compaction.
- Seal the surface with a second application of calcium chloride, applied at the rate of 0.25 gallons per sq. yd. (1.3 liters per sq. meter).
CALCIUM CHLORIDE OUTSTRIPS ASPHALT EMULSIONS
In full depth reclamation, calcium chloride presents several advantages over asphalt emulsions:
- Economical: Calcium chloride costs half as much as asphalt emulsions. And calcium chloride’s natural viscosity facilitates compaction, so you can achieve a more stable road base with less work–which translates into significant labor and equipment savings.
- Improved bond: Calcium chloride helps absorption of bituminous materials. Priming materials are readily absorbed and there is no blocking of bituminous materials due to dust film.
- Frost protection: Small percentages of calcium chloride are effective in reducing detrimental frost action. Work done at Perdue University concluded that calcium chloride, in a stabilized mixture, prevented detrimental frost heaving.
- Versatile: Calcium chloride can be used as an additive for reclaiming a wide range of road types.
- Controlled curing for increased stability: Results show that calcium chloride used in the mix assures a high structural stability, because it controls a high rate of drying in both the compaction and curing periods.
APPLICATION TIPS FOR FULL DEPTH RECLAMATION
- Use a vibratory roller. It can make a difference in road hardness because it offers greater compaction–especially with calcium chloride, which lubricates the particles so they move close together.
- Check drainage. The road should have adequate cross-fall, shoulders, ditching and other drainage features.
- The total amount of 35% liquid calcium chloride to be used is 1 gallon per sq. yd. (5.2 liters per sq. meter). To ensure that the liquid calcium does not run off, application by distributor truck might require multiple passes.
- The base course with liquid calcium chloride should be allowed to cure for several weeks prior to construction of the final wearing surfaces. The length of time necessary for proper curing will vary depending on weather and environmental conditions.
- Wearing surfaces may consist of a single or double seal coat, or varying thicknesses of cold mix or hot asphalt mix, depending on traffic load.
GENERAL NOTES ON USING CALCIUM CHLORIDE
Make your initial seasonal application of calcium chloride in the springtime, as soon as possible after roads have received their final shaping. Calcium chloride can be applied in either liquid or flake form.
Liquid calcium chloride
In liquid form, calcium chloride works best when applied just before roads become dry and dusty. Liquid calcium chloride will always add moisture to the road, but it penetrates better and is more effective if used to retain moisture already present.
Liquid calcium chloride is generally sprayed as a 35% solution, using a tank truck with a rear-mounted distribution bar that spreads the liquid evenly over the road. Approximately 2200 gallons per mile (4663 liters per km.) will cover a 12-foot wide (3.75 meter) road.
Apply liquid calcium immediately after spring shaping, before the road has dried from spring rains. Liquid calcium chloride is normally applied at the rate of 0.4 gal. per sq. yd. (2 liters per sq. meter). For proper road treatment, apply a second time later in the summer, at the rate of 0.1 gal. per sq. yd. (0.5 liter per sq. meter).
Flake calcium chloride
In spring, flake calcium chloride should be applied while the road is still moist, before dust appears. Apply flake calcium chloride evenly and uniformly over the road’s surface within one foot (⅟₂ meter) of either side. On previously treated roads, application rates range from low ⅟₂ lb. per sq. yd. (0.3kgs. per sq. meter), for a road having carry-over and light traffic, to 2 lbs. per sq. yd. (1.2 kg. per sq. meter). On new roads that have been previously treated, application rates vary from 1 ⅟₂ to 2 lbs. per sq. yd. (0.9-1.2kg. per sq. meter), depending on the type of composition of the surface and traffic count. An additional application of ⅟₂ to ¾ lb. of calcium chloride per sq. yd. (0.3-0.45 kg. per sq. meter) should be made later in the season when the surface shows signs of dusting.
During periods of hot, dry weather, the surfaces of dense, well-compacted roads should be sprinkled with water just before the application of the flake calcium chloride. This speeds the dissolving of flake calcium chloride, and prevents the flakes from being thrown off the road’s surface by traffic before they dissolve.
Several varieties of spreading equipment are suitable for applying flake calcium chloride, including tailgate, spinner disk and drill-type spreaders. Peters Chemical will help you determine the right spreader for your application, taking into consideration the uniformity of coverage, ease of regulating the rate of spread, and width of spread required.
Aggregate requirements for optimum results
A stable unpaved road contains a naturally or mechanically balanced mixture of local materials compacted into a smooth, dustless surface with moisture obtained from the air and maintained by calcium chloride.
For the best results when stabilizing an unpaved road, incorporate calcium chloride into the base during a road rebuild. The optimum formula is to apply 1% calcium chloride by weight to selected gravel materials. For proper stabilization, a well graded crushed aggregate is recommended, with 80% of it having fractured faces and 3 to 12% by weight being able to pass through a #200 U.S. sieve. The road should also have adequate cross-fall, shoulders, ditching and other drainage features.
A typical unpaved road treated with calcium chloride contains surfacing materials ranging in size from coarse aggregate (two inch maximum) to the very finest particles of binder and soil. A two-inch top size aggregate is considered maximum for easy blade maintenance.
The smaller-sized particles must be present in sufficient quantities to fill the spaces between each of the larger sizes. The binder soil, kept moist by treatment with calcium chloride, remains plastic, keeping voids filled. Traffic will compact the graded particles into place, interlocking them to form a dense, smooth-riding surface with sufficient strength to carry normal wheel loads. The surface thus formed is sufficiently tight and compact to prevent penetration by water from rain or melting snow.
To achieve lasting stability, road surfaces of this kind should meet the surface course gradation recommendation of the American Association of Highway and Transportation Officials.