Road Base Stabilization Process

PROCESS VARIATIONS

• Central Plant Base Stabilization: New or in-place aggregates are imported to a central location and stockpiled for future use. The materials are mixed in a pugmill mixer. The pugmill mixer has an aggregate feed conveyor belt with a belt scale linked to a computerized liquid stabilizing agent, water and additive system that accurately meters the materials into the pugmill based on the weight of the aggregate. Dry stabilizing agents are typically transferred via silo augers or separate transfer devices tied to the belt scale. The aggregate is processed and hauled to the site for placement and compaction
• Onsite Base Stabilization (New Construction): Aggregates are hauled to the site and placed on a prepared subgrade. Stabilizing agent is added and the materials are mixed and compacted on the prepared subgrade
• Reconstruction: RAP is milled from the existing pavement and hauled to a processing site. The exposed aggregate base is then mixed with a stabilizing agent and compacted

Equipment

The equipment used to perform Base Stabilization will vary from contractor to contractor, but no matter how configured, the equipment performs the same general steps. The equipment requirements for Base Stabilization depend on the specifics of the project but generally consists some or all of the following:

• Modern, high horsepower self-propelled reclaimer
• Pugmill mixer for central plant applications
• End or Bottom dump haul trucks
• Calibrated bulk spreader for dry stabilizing agents
• Mixer and tanker for slurry application of stabilizing agents
• Emulsion or hot asphalt tankers for bituminous stabilization
• Computerized emulsified asphalt or foamed asphalt injection system on the reclaimer
• Motor grader
• Water truck with spray bar 
• One or more compactors (pneumatic-tired, pad foot and/or double drum vibratory rollers)

Chemical Stabilization is achieved with the addition of cement (portland or hydraulic), lime (hydrated or quicklime), self-cementing class C fly ash, class F fly ash (when used in combination with other additives), cement kiln dust (CKD), lime kiln dust (LKD), calcium chloride, magnesium chloride or proprietary products to the pulverized materials.

Bituminous Stabilization is accomplished with the addition of emulsified asphalt or foamed (expanded) asphalt to the pulverized materials.

Base Stabilization + Single or Double Chip Seal: A surface course is required over base stabilized sections and where the pavement structure is sufficient to carry the anticipated loads, chip seals are very economical.

Base Stabilization + Micro or Slurry Surfacing: Where the reclaimed pavement structure is sufficient to carry the anticipated loads micro or slurry surfacing are additional economical surfacing options. 

Base Stabilization + Asphalt Surface: To increase the structural capacity of the pavement structure, an asphalt mix can be placed over the stabilized base layer. 

Base Stabilization + Cold Mix Surface: For low volume pavement applications, a cold asphalt mix or CCPR asphalt mix can be placed over the stabilized base layer. A seal coat may be required to prevent moisture infiltration.

Base Stabilization + Concrete Surface: A stabilized base layer can be used as a non eroding base in a rigid pavement structure.