Marshall Stability Testing for the Earthbind® Stabilization Process

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Earthbind® Stabilizer is considered to be an environmentally-friendly, modified asphalt emulsion that is specifically engineered for base, sub-base, and sub-grade stabilization.

Earthbind Stabilizer ships in a concentrated liquid form and is diluted with water for application purposes. For a stabilization process, the diluted Earthbind solution is incorporated and mechanically mixed into a soil/aggregate material…several inches in depth using a reclaimer/stabilizer. After the solution and soil/aggregate has been mixed, the amended material is then profiled with a motorgrader and compacted with a roller to maximum dry density at optimum moisture. Once the water used to make the Earthbind solution dries, the product is considered to be cured. Earthbind stabilization does not require heat for the stabilization process.

Earthbind stabilization is considered to be a bituminous stabilization process. With bituminous stabilization, strength gain is achieved by coating aggregate particles and adhesive bonding. The benefits of Earthbind stabilization can include:

  • Improving the strength and durability of the soils/aggregate matrix
  • Adding water-resistance to the treated material
  • Conserving the fines, reduces dusting and mitigates aggregate from unraveling
  • Upgrading marginal material that are typically undesirable for the sub-grade or for road base construction
  • Greatly reducing maintenance activities and maintenance costs
  • Helping reduce/eliminate wash-boarding
  • Helping minimize potholes (in combination with adequate drainage)
  • Providing temporary or permanent (with maintenance) wearing surfaces on unpaved low-volume roads
  • Reducing pavement thickness requirements on road bases that will be paved.

Earthbind Stabilizer works on a variety of soil/aggregate types. However, Earthbind stabilizer is commonly used to stabilize road bases constructed with ¾” minus engineered aggregates with material greater than 20% passing the #4 sieve, a fines content (silt and clays passing the #200 sieve) less than 20%, and plasticity index of less than 15.

The aggregate/soil material type and gradation will influence the amount of Earthbind to be used in the stabilization process. It is strongly recommended that a laboratory mix design is performed by a geophysical laboratory to verify and determine the suitable concentration of Earthbind Stabilizer that meets project performance requirements for a specific soil/aggregate.

At present, there is no nationally accepted laboratory mix design method for bituminous base stabilization. For chemical stabilization (e.g., cement stabilization) unconfined compressive strength testing is often done whereas the Marshall Stability test is frequently performed for bituminous stabilization mix design testing. We consider the Marshall Stability test (ASTM D6927/ASSHTO T245) or some appropriate variant of the test, to be suitable to determine the optimum amount of Earthbind Stabilizer to meet maximum compressive load. It should be noted that typically the material stabilized with Earthbind is considered to be dense-graded mixtures.

The Marshall mix design can be used to determine the optimum Earthbind binder content. The Marshall Stability and Flow tests provide the prediction of performance for the Marshall mix design method. The stability portion (e.g., Marshall Stability) measures the maximum compressive load of a test specimen where the maximum load is designated as stability. In addition, a flow value (e.g., Flow) can be recorded at the same time when the maximum stability load is recorded. In a nutshell, the Marshall test for stabilization includes samples composed of soil/aggregate that are mixed with differing concentrations of the Earthbind binder and water (i.e., commonly 1 to 5% by weight), then transferred to a metal mold and then compacted with 50 or 75 blows on either side with a 10-pound hammer dropped from 18” in height. The samples are then extracted from the mold and allowed to cure. After curing the samples are compressed using a load frame to determine the stability and flow.

The compressive strength achieved by the Earthbind amendment can be compared to the Marshall Mix Design criteria from the Asphalt Institute (MS-2, 7th edition). These stability values are used to determine the strength of asphalt paved road but can be used to qualify the strength gained on bitumen stabilized materials. For comparisons, the minimum Marshall design criteria for stability for light traffic roads is 500-pounds (2224 Newtons), for medium traffic roads is 750-pounds (3336 Newtons), and for heavy traveled roads is a minimum of 1500-pounds (6672 Newtons). It is common that soil and aggregate material stabilized with Earthbind Stabilizer can exceed the minimum stability values for light, medium, and heavy traffic roads.

In conclusion, bituminous stabilization using Earthbind stabilizer can be a viable alternative to chemical stabilizers. The efficacy of using Earthbind stabilizer can be easily determined using Marshall Mix design testing.

For more information on Earthbind stabilization, please contact a sales engineer at