District Materials Engineers typically provide oversight responsibilities for inspection and/or monitoring at HMA plants.  They should assure themselves that plant inspectors are qualified and have been informed about their specific duties.  This should include, but not be limited to, frequency of tests, information to be recorded, and samples to be obtained and submitted to Central Materials and District Materials laboratories.


Plant inspectors should be placed in charge of all plant inspection.  Their personal duties include checks of stockpile handling, equipment settings, mixture appearance, and supervision of scale inspectors and assistant plant inspectors.  Plant inspectors should be instructed to avoid spending prolonged periods in the laboratory trailer.


Refer to Materials I.M. 508 and Construction Manual 3.07 for HMA plant inspection requirements and documentation.


Certified plant inspection will be required for Interstate, Primary, state park, and institutional projects.  It will apply to other projects only when designated.  All HMA production, including HMA for patching, will be covered by certified plant inspection unless otherwise excluded by contract documents.  The contractor shall furnish and be responsible for certified plant inspection in accordance with Specification 2521 and Materials I.M. 213.


On Quality Management - Asphalt (QM-A) projects, the contractor's certified HMA technician is responsible for meeting all sampling, testing, and documentation requirements as set forth by the current specification.  For some contractors, this person may also be responsible for certified plant inspector duties as well.  It should be possible for two people to handle both QM-A and Certified Plant Inspection (CPI) responsibilities on a typical HMA resurfacing or paving project.   If the contractor fails to staff a project adequately for QM-A and CPI activities to be accomplished in a thorough, timely, and proper manner, a noncompliance should be issued.  It is not a requirement that the certified HMA technician personally obtain the hot box samples from behind the paver.  This operation can be assigned to any of the contractor’s personnel as long as that person is a certified HMA sampler.  This allows the certified HMA technicians to spend their time in the lab rather than on the road, providing for more efficient use of technician time as well as timelier test results.  The certified HMA technician should maintain good communication with the plant monitor and District Materials personnel on test results and mix changes.


Plant monitor requirements for QM-A projects are also described in Construction Manual 3.07.



Project engineer is responsible to insure that mixing time is inspected on continuous plants and on batch plants.


Necessary action shall be taken to insure compliance with mixing time requirements.  Inspectors shall check mixing time when work begins on the project and thereafter as they consider necessary to insure compliance.  Inspector's diary must show when it is done and calculations used.  Inspection procedure is described in Materials I.M. 508 and should be followed carefully.


If mixing time is found to be deficient, inspector shall see that contractor increases it to specified amount.  For continuous plants, this is done by decreasing megagrams (tons) output or by increasing pugmill contents.


Materials personnel will give assistance in determining the mixing time as a component of the plant calibration process.