Ultra Thin Lift HMA

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Primary Resource

The inspector plays a vital role on every construction project ensuring that the completed operations comply with the plans and specifications. Information on where to obtain the best practice guidelines and additional  resources can be found in the Additional Resources section. As with any construction process, if the owner agency is concerned with any part of the process, the owner agency should have a conversation with the contractor. 

Inspection Guidelines

Inspection Guidelines

Like most paving projects, the primary goal is to produce a strong, smooth and durable wearing surface. Inspectors can help achieve this goal by ensuring that the process is in accordance with the contract documents as follows:

Mix Design: Verify that a mix design(s) was performed by a qualified lab resulting in a mixture that meets or exceeds the contract documents.

Surface Preparation: Walk or drive the entire pavement to be paved for the day to ensure the surface has been properly prepared and that all pre-construction repairs have been made.

Acceptable Weather: Measure the air and pavement temperature and check conditions for anticipated rainfall to determine if construction can start.

Traffic Control: Verify that the proper traffic control is in place to keep the traveling public safe and out of freshly placed mixture.

Quality Equipment:

  • Verify that nozzles and spray bars on the tack distributor are working properly and are not plugged.
  • Verify that aggregate cold feeds have been calibrated.
  • Verify that all cold feed gates and belts are in working order.
  • Verify that the plant is properly calibrated and that all scales, guages and meters have been checked for accuracy,
  • Check the mixture for uniformity, homogeneity and temperature as it is discharged from the plant.
  • Verify that the haul trucks are of the required type, number and size and that tarps are working properly.
  • Verify that the compaction equipment is of the required type, number and size and that scrapers and spray bars are properly working.

 Quality Workmanship:

  • Verify that all stockpiles are clearly marked, separated and free of contamination.
  • Verify that the existing pavement surface has been tacked.
  • Verify that the plant is producing the mixture at the proper temperature.
  • Verify that the mixture is being placed to the proper depth, grade and cross-slope.
  • Ensure that the transverse and longitudinal joints are properly constructed.
  • If required, verify that a control strip was established to determine proper compaction procedures.
  • Verify that the rolling procedure established in the control strip is followed and that the compacted density is within the specified range. Reestablish the rolling pattern if the density of the mixture is not in compliance.

Application Rates: Periodic checks should be made to verify that the material being placed is within the allowable tolerances.

Additional Resources

  • Pavement Preservation Checklist Series 3, Thin Hot-Mix Asphalt Overlay, FHWA and FP2. www.fhwa.gov/pavement/preservation/ppcl03.pdf
  • NCHRP Synthesis 464 Thin Asphalt Concrete Overlays, A Synthesis of Highway Practice, Transportation Research Board, Washington, D.C. 2014. http://www.trb.org/Main/Blurbs/171104.aspx
  • Thin Asphalt Overlays for Pavement Preservation, IS-135E, National Asphalt Pavement Association, July 2009.