Asphaltic Paving | Sub-Grade Preparation | Spreading and Compaction

 

Reference Documents:  
   
640.108 Asphaltic Concrete

 

  1. Preparation
    1. The specifications require the use of asphalt testing laboratories and their inspectors for much of the QC documentation. As per 4WCE-600001, the contractor is responsible for all QC testing and coordination.  Before starting, make sure arrangements have been made.
    2. The asphalt inspector is subject to the same safety regulations as everybody else on site.
    3. Paving companies will be familiar with some safety requirements, but not all. Make sure that the contractor’s superintendent knows all of the rules to working on an Air Products site.
    4. The paving company shall make provisions for all signs, cones, flags, and people needed to direct or slow traffic down for them to work safely. In some jurisdictions, a traffic plan may need to be submitted and approved if paving activity will encroach upon public roadways.
    5. All design mixes, soil stabilization fabric, binders, sealers, and other materials that are not specified on the contract drawings will need approval by the assigned civil engineer.
    6. The contractor needs to submit a design mix for each mix of asphalt being installed. Along with the mix designs, the contractor should also submit test data certifying that the mix as designed will meet Air Products requirements.  These requirements can be found in specification 640.108.
    7. The contractor also needs to submit a sample for testing and confirmed adherence to the requirements. If the local Department of Transportation mix is to be used, certified test results from within the past year are acceptable.
    8. The Air Products superintendent should visit the mixing plant with the asphalt inspector. All of the required tests listed in 640.108 shall be reviewed with the mixing plant to confirm their conformance and support when tests are needed.
    9. Have contractor make the necessary arrangements for testing laboratory personnel to be at the mixing plant during the mixing, to assure asphalt compliance. If a certified DOT inspector is located at the batch plant full time, ask the contractor if copies of his reports can be forwarded to Air Products.
  2. Sub-Grade Preparation
    1. The sub-base needs to be to grade and profile as defined on the design drawings. Correct sub-base road profile is essential for achieving a correct finish grade.
    2. Sub-base shall be compacted to the required density as defined in the specifications.
    3. Ensure that water will not gather in low lying areas or behind structures and flows towards drains or onto pavement shoulders.
    4. Look for areas where water could become trapped along the roadway. Consider an “underdrain” at those locations to prevent future over-saturation of the road base.
    5. Have the testing laboratory confirm the proper compaction and water content in the sub-base prior to placing any soil stabilization fabrics or sub-grade, with a nuclear density test.
    6. Ensure the soil stabilization fabric is installed as per the manufacturer’s instructions.
    7. The crushed rock sub-grade needs to be the correct material and thickness as noted on the contract documents. Ensure that no organic matter is mixed with the rock.
    8. Verify the sub-grade has been properly shaped to allow drainage. Look to see if there are soft or “pumping” areas in the sub-base and sub-grade where the base is too wet and needs to be excavated and replaced.
    9. After placing the sub-grade, the contractor should “proof-roll” the area using a loaded dump truck. As it moves around, note any soft areas, and have them replaced.
    10. In some areas, the sub-grade needs to be primed prior to placement of asphalt, usually 24 hours before. Check with the Air Products civil engineer for particulars.
    11. If placing paving above existing pavement or a cold binder layer, then a tack coat will be needed prior to placement of the new course.
  3. Spreading and Compaction
    • During mixing of the asphalt, Air Products requires that the testing laboratory do daily extraction tests for bitumen content and aggregate gradation. These tests should verify that the mix is conforming to the design.  See 640.108 for specifics.
    • Bitumen should not be placed on wet surfaces or when the surface temperature of the underlying course does not comply with 640.108. Check the temperature of the surface to see if it is lower than 50 F.
    • The asphalt, when warm enough, should be loose and flowing. There shouldn’t be large chunks, which may indicate that the mix is bad, or too cold.
    • Asphalt spreading temperatures shall be 275-325F.
    • Longitudinal joints through succeeding courses are offset a minimum of 6”. No course shall exceed 4” in compacted thickness.
    • Check the pitch of the asphalt with a level to verify that water will drain in the correct direction. Check once before they start roller compacting and again after several passes to confirm.
    • Occasionally, squat down and look along the paved area to note the finished profile. Look for dips where the grade has changed and puddles could form.
    • On all paved roadways inspections need to be run every 100’ or every 50’ if the road will see a lot of truck traffic
    • On all paved truck staging or parking areas, testing should be done every 2500 sq. ft. or every 625 sq. ft.
    • Some of the tests that should be done are:
      1. Nuclear density testing of the subgrade
      2. Nuclear density testing on each course of paving
  • Record temperatures of the asphalt being spread
  1. Core samples of the finished product, after cooling
  1. Final acceptance will be after the core samples have been verified that they comply with the mix design.
  2. Most paved areas will have 3’ wide tapered shoulders. They shall be compacted to within 95% of compacted dry density.
  3. Lines in the pavement to mark parking stalls or to separate walkways shall be spray applied 4” wide chlorinated rubber yellow traffic paint.
  1. QC Documentation
    1. Certifications of testing laboratory and technicians.
    2. Calibration certificates for test equipment
    3. Approved mix design
    4. As-built drawings, indicating repaired soft spots, core sample locations, changes in the surface profile, changes in the paving cross section, or other related items of note.
    5. Nuclear density compaction test reports on sub-grade and sub-base
    6. Nuclear density compaction test reports on each course of paving
    7. Daily bitumen and gradation test results
    8. Recorded temperatures of asphalt being placed.
    9. Core sample reports

 

 


 

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