Applying Dust Control

Effective dust control is built on a foundation of quality gravel. The proper mixture of fine material and larger aggregate is important to ensure natural binding action. When calcium chloride is applied to this gravel mixture, moisture is drawn from the air to keep the surface damp and the mixture tightly bound. For best performance, aggregate should meet these criteria:

Recommended Aggregate Characteristics

Characteristic Preferred Acceptable
Maximum Size 3/4 inch 1 inch
Grading Description Well graded - not uniform or skip graded  
Percent Pass #4 55 to 70 50 to 70
Percent Pass #200 (Nonplastic) 14 to 17 12 to 17
Percent Pass #200 (Plastic) 12 to 15 8 to 15
Plasticity Index 2 to 9 Nonplastic
Los Angeles Abrasion Less than 30 Less than 40
Percent Fracture, one face Greater than 85% Greater than 75%


A season-long dust control program should begin in the spring. Blade the road while the moisture content and humidity are relatively high. Water the road surface prior to blading unless rain has fallen within the previous two days. Remove ruts, washboards and potholes, and mix in loose aggregate. Good drainage is essential. Shape roads to a 4% or greater crown. Ditches, shoulders and culverts should be reshaped and cleaned as needed. Calcium chloride should not be applied during heavy rainfall or if rain is threatening because rain will leach out or dilute the chloride and cause it to run off of the road.

Recommended application rates are provided below. When applying solid products, it is usually preferable to water the surface prior to spreading the product. If the road is kept open to traffic while solid product remains on the surface, signs should be posted directing motorists to take appropriate precautions as road surfaces may be slippery. There should be no health threat to motorists or pedestrians as long as recommended application procedures are followed. See Material Safety Data Sheets (MSDS) for individual products to review complete health and safety information.

To maintain optimum dust control during unusually long periods of hot, dry weather, water the road surface during early morning hours as needed to reconstitute the initial treatment. Re-apply calcium chloride in the late summer or early fall as needed to prolong dust control.

Recommended Application Rates (US Units):

Product  Unpaved Roads Truck Terminals & Parking Lots Mine Haul & Logging Roads
LIQUIDOW™ 35% 0.30 gal/yd2 0.33 gal/yd2 0.39 gal/yd2
  2117 gal/lane-mi* 2532 gal/lane-mi 2744 gal/lane-mi
LIQUIDOW™ 38%  0.27 gal/yd2 0.30 gal/yd2 0.35 gal/yd2
  1901 gal/lane-mi 2112 gal/lane-mi 2464 gal/lane-mi
LIQUIDOW™ 42% 0.24 gal/yd2 0.26gal/yd2 0.31 gal/yd2
  1664 gal/lane-mi 1849 gal/lane-mi 2157 gal/lane-mi
DOWFLAKE™ Xtra 83-87% 1.38 lb/yd2 1.56 lb/yd2 1.83 lb/yd2
   4.84 ton/lane-mi 5.49 tom/lane-mi 6.45 ton/lane-mi
Anhydrous 94-97% 1.23 lb/yd2 1.39 lb/yd2 1.64 lb/yd2
  4.33 ton/lane-mi 4.90 ton/lane-mi 5.77 ton/lane-mi

*lane-mile equals 4 yards wide by 1760 yards long

Recommended Application Rates (Metric Units):

Product  Unpaved Roads Truck Terminals & Parking Lots Mine Haul & Logging Roads
LIQUIDOW™ 35% 1.36 liter/m2 1.51 liter/m2 1.76 liter/m2
  5027 liter/lane-km* 5604 liter/lane-km 6511 liter/lane-km
LIQUIDOW™ 38% 1.22 liter/m2 1.36 liter/m2 1.58 liter/m2
  4514 liter/lane-km 5032 liter/lane-km 5846 liter/lane-km
LIQUIDOW™ 42% 1.07 liter/m2 1.19 liter/m2 1.38 liter/m2
   3951 liter/lane-km 4404 liter/lane-km 5116 liter/lane-km
DOWFLAKE™ Xtra 83-87% 0.75 kg/m 0.85 kg/m2 0.99 kg/m2
  2.76 tonne/lane-km 3.13 tonne/lane-km 3.68 tonne/lane-km
Anhydrous 94-97% 0.67 kg/m2 0.76 kg/m2 0.89 kg/m2
   2.47 tonne/lane-km 2.80 tonne/lane-km 3.29 tonne/lane-km

*lane-km equals 3.7 meters wide by 1000 meters long