The following instruction is to be used when monitoring the operation of an asphalt plant. The plant monitor is responsible for monitoring the plant operation, quality control procedures performed by the certified plant inspector, and ensure that proper mix is being produced and delivered.




The following duties are performed by the plant monitor for asphalt paving.




Minimum Frequency

1. Inspect stockpiles

• Observe stockpiling procedures.

• Check for segregation.

• Check for contamination. 

• Check for degradation.

• Check for proper storage and handling of aggregates per Article 2303.03 C 3.

• Check that the stockpiles being loaded into the bins match the mix design.

Observe during startup and during visits

2.  Mix Design

• Verify that a valid mix design exists and has been signed by the DME.

• Check that any changes to the mix design are properly documented.

At start up and before each new design.



• Verify that the mix design being produced matches the bid item being placed.


3.  Test Equipment

• Inspect test equipment to ensure it is in good working order and lab has been qualified.

During startup and when problems arise

4.  Material certifications

• Check certifications for binder, aggregates, and RAM. Verify that the material delivered meets the mix design and materials requirements of 2303.02.

During visits

5.  Observe aggregate and mixture sampling and testing.


• Observe tests are performed in accordance with Materials IM’s and at the frequency listed in IM 204.

• Direct and witness binder and aggregate samples for verification testing.

• Fill out form 193 for binder aggregate and mixture samples and secure for transport per IM 205 Appendix A.

During daily visits

6.  Plant proportion control

• Observe delivery tolerances.

• Observe scale check and verification weights per 2001.07 A 7.

• Check that mix proportions settings in the control house match the approved mix design.


7. Compacted mixture density.

• Witness or verify that agency personal direct and witness coring.

•Transport or verify that sample security has been maintained.

• Check cores for damage with the CPI before testing.

• Test cores, record and furnish the results to the CPI.

During visits


8.  Audit Daily Diary

• Review for proper recording of events.

During visits

9.  Plant Reports

• Check for proper project bid item and mix identification.

• Check for dates and report number.

• Check for proper placement records (stations, widths for PWL & non-PWL)

• Check for recorded air, binder, mix and mat temperatures.

• Check binder quantities against totalizer in the control house.

• Check for locations on hot boxes.

• Check for proper documentation of mix changes.

• For small quantities 2303.03 E., check that the certification statement is in the remarks.

• Review test results and aggregate gradations.

• Check materials sources.

• Check for correct binder, aggregate and RAM totals (daily, weekly, and to date).

• Check for appropriate Plant Inspector signature or initials.

• Sign report after review.

• Check for hard copy or electronic backup of files

Daily / Weekly

10.  Monitor dump trucks

• Check for properly cleaned dump box.

• Check release agents.

• Watch for inappropriate use of solvents per 2001.01 D.

During visits

11.  Inspect plant facility

• When available observe plant calibration to assure compliance with Materials IM 514.

• Check for calibration report.

• Check lab qualifications. 

• Inspect test equipment.

At start of project


A monitor checklist is available at: http://www.iowadot.gov/Construction_Materials/hma.html




A Non-compliance Notice (Form #225) shall be immediately delivered to the acting representative of the contractor for the area of construction involved whenever procedures or tests results on acceptance samples representing material to be incorporated or incorporated in the work indicate non-compliance with the specifications and plans. Appropriate action in accordance with the applicable specifications and Instructional Memorandums shall be taken.


Identification of Sample for Test (Form #193)


This form must accompany all samples submitted to the Central Laboratory and District Laboratories. Examples of completed forms have been included in this instruction.  A copy of the 193 form may be found at: http://www.iowadot.gov/Construction_Materials/hma.html