Road Stabilization

A road is only as strong and durable as its base . . . and the stability of the road depends on the proper interlocking of the aggregate. Calcium chloride:

  • penetrates the road aggregate, coating the particles and binding them together. Binding action keeps the road dense and compacted
  • speeds compaction of the base materials
  • maintains moisture in road base to minimize the loss of fines, and maximizes the service level of the wearing course.
  • reduces gravel costs during construction and maintenance
  • provides a cost-effective alternate in recycled asphalt bases

Town of Caledon Trial and method of application:

General Chemical contracted Trow Inc. to select the test and control sites and to perform all the testing before and after reclamation.

Trow engineers designated a 150 m (164 yd.) stretch of Chinguacousy Road as the test section. Across a 20 m (22 yd.) buffer zone to the north of the test section, engineers staked out another 150 m (164 yd.) control section. Both sections were rehabilitated but no calcium chloride was added to the control section. Soil samples were taken at staggered intervals from both the test section and the control section before and after pulverization.

Testing of the existing subgrade soil found clayey silt to silty clay till. The granular was a mixture of sand and gravel, predominantly hard carbonates generally varying in thickness from 220-300 mm (9-12 in.) The bituminous surface of the road was a heterogeneous mixture of hot mix asphalt and surface treatment of a uniform thickness of 60-80 (2.5-3 in.).

The reclamation work was contracted out but all other work was done by the Town. The test and control sections were reclaimed between August 9 and 11, 1989 using the following procedures, Stabilizing a road with calcium chloride consists of 7 steps:

Step 1 Scarification of road surface:

Pulverize the existing bituminous surface with the underlying granular to a design depth of approximately 150 mm (6 in.) using one pass of a Reclamer 1 PulviMixer.

Step 2 Addition of aggregate:

Place additional imported gravel granular base course to the test section and control section using end-dump and belly-dump methods, and apply water using tanker truck with spray bar attachment to achieve suitable moisture conditions. The total average additional granular thickness was approximately 50 mm (2 in.) after grading and shaping;

Step 3 Application of calcium chloride:

Apply liquid calcium chloride to the test section granular base at a rate of 3.6 liters per square meter (.75 gallon per square yard) 35 percent solution.

Step 4 Mixing of materials:

Mix the loose granular and calcium chloride with one pass of a Reclaimer 1 Pulvi-Mixer.

Step 5 Shaping and cross section:

Grade and shape the full road width to restore crossfall.

Step 6 Compaction of surface:

Compact loose granular using a single steel drum vibratory compactor.

 
Step 7 Seal surface with calcium chloride Spray compacted granular surface of roadway with liquid calcium chloride at a nominal rate of 1 liter per square meter (.25 gallon per square yard). The total volume represents approximately 1 percent calcium chloride by weight of dry aggregate weight for 150 mm (6 in.) layer thickness. The road was then left open to traffic for three weeks before the Town applied a double surface treatment of stone chips and emulsion.

    Testing
  • Soil samples were taken and engineering tests were conducted before and after the surface treatment was applied.
  • Dynamic load and deflections were measured at two different dates, 48 days apart, using a Falling Weight Deflectometer.
  • Saw-cut and test pit samples were taken for laboratory testing.
  • Tests for resilient moduli were carried out on closed-loop electrohydraulic MTS equipment at McMaster University in Hamilton, Ontario.

Other Reports

 

1) Trow Ltd., “Calcium Chloride Use for Gravel
Road Stabilization and Strengthening, Foss
Road Trial, Pelham Ontario,"1985.

Calcium chloride was applied at various concentrations on different parts of the test road making sure it was well mixed into all materials for maximum penetration. Out of this trial came a recommended method for optimum base stabilization.

  • Depending on local conditions, new materials should be granular A in which 10-15% of fines pass a No. 200 sieve.
  • Calcium chloride should be applied at a rate of 1% by weight of materials.
  • Calcium chloride should be thoroughly mixed with all materials to ensure a penetration to the full-depth 150 mm (6 in.) of the granular material.
  • The road should be compacted with a smooth drum vibratory compactor.

Although the optimum rate of application is 1% calcium chloride by weight, results showed calcium chloride contributed to the strength of the road regardless of its application rate or penetration. Unlike some stabilizing agents, such as oil emulsion, calcium chloride allows room for error.

2)CALCIUM CHLORIDE:
Adds Strength and Durability
Emery, J. “Evaluation of Calcium Chloride
Base Stabilization Trials,
Town of Pelham, Ontario," 1986.

Further testing by JEGEL showed that, if a road is carefully stabilized according to the recommendations established by Trow in 1985, a Granular Base Equivalent of 1.3 can be expected. In other words, compared to a road with a granular A base, a road with the same base, but stabilized with calcium chloride, would be 30 percent stronger and more durable. That means calcium chloride roads will last longer.

3) The American Road and Transportation Builders Association estimates that calcium chloride will double the life of a paved road that has been stabilized to a depth of 150 mm (6 in.) and surfaced with 50 mm (2 in.) of asphalt.