Asphaltic Concrete Pavement Stabilization and Lifting

Problem:

Poor foundation soils under asphaltic concrete pavement. The poor and/or uneven support can result in premature cracking, rutting, and settlement of the pavement. Insufficient soil strength may be caused by:

  • Loose or un-compacted foundation soils that were untreated prior to construction of roadway.
  • Water infiltration into the foundation soils through cracks in the pavement.
  • Roadway was widened but proper stabilization of the foundation soils was not practical.
  • A mission change for the roadway (such as in the oil/gas boom area) where the original design is now insufficient – the thicker pavement now required for the heavier loads also requires a thicker base/sub-base.

Solution:

Apply the URETEK Deep Injection Process with URETEK 486 water resistant expansive polymer at a typical depth of -4′. If DCP tests show deeper problems, additional depth(s) of injection can be added as needed. This is accomplished by drilling multiple 3/4″ holes through the asphaltic concrete and injecting through tubes into the foundation soils. Depending on the thickness of the asphaltic concrete pavement, this may be performed on as tight a pattern as a 3′ by 3′ grid or the traditional 4′ by 4′ grid. URETEK monitors the surface using laser monitors and/or dial indicators and knows that the pavement structure in that strata of injection has become adequately stabilized when an indication of movement is detected on the monitors. It is necessary to inject through tubes at depth because asphaltic concrete is a flexible pavement. If injected directly under the pavement or too close to the surface, the forces created by the expansion of the polymer will blister the flexible pavement and create an uneven pavement surface.

Expected Results:

  • Compact the loose foundation soils without uneven lifting of the flexible pavement to provide sufficient support of the pavement surface.
  • Continued injection into the soils can lift the pavement system if needed.
  • Lifting of the rutting is NOT possible.
  • Surface cracks will still need to be sealed by traditional methods to mitigate water infiltration into the system.

Benefits:

  • Zero daytime lane closures.
  • Removal of good asphaltic concrete pavement and poor foundation soils is not required – saving time and money with a sustainable solution.
  • Overlay to correct rutting can be performed immediately following the polymer injection into the soils.
  • Extends the life of a new overlay.
  • Injection can be accomplished in wet soil conditions as the URETEK 486 STAR hydro-insensitive polymer will form a dimensionally stabile polymer even when injecting into saturated soils. The expansion process will also drive the water out of the soil system.

Alternates:

  • Injecting a concrete slurry directly below the asphalt or at depth under the asphalt is typically not a design option as it will create a very uneven roadway surface due to the relatively high pressure at which the slurry needs to be pumped. In addition, the slurry does not migrate very far from the injection point resulting in a “mushroom” effect, creating unintended, uneven lifting.
  • Injecting a polymer directly under an asphalt surface will blister the asphalt and lift unevenly resulting in a very uneven roadway surface, requiring an overlay of the pavement.
  • Removal and replacement of pavement, along with the base and weak foundations soils, is extremely expensive and causes significant traffic delays.

Reference Documents:

    1. MODOT Carroll County Project Report – Contains pre-injection and post-injection Falling Weight Deflectometer (FWD) test results and analysis performed by MODOT. Results were extremely favorable and engineer remains satisfied with the project. Read Report.
    2. Penn State University Demonstration – Summarizes the demonstration URETEK performed in 2012 at the request of PennDOT. View Demonstration.
    3. TXDOT SPID Asphalt Stabilization Project in 2001, Corpus Christi, TX – Stabilization at -4′ of an unstable asphalt pavement prior to overlay, the project was a success and 13 years later continues to provide the required pavement support. View video below.