The Central Materials Laboratory (CML) will accredit the District Materials Laboratories and maintain records of the accreditation for five years. The CML Staff will check the following prior to accrediting a laboratory:


1.   Check for current manuals and test procedures covering the accredited testing.

2.   Check the certification and training records of the testing personnel.

3.   Document that proper equipment is available to perform qualified testing.

4.   Check documentation system.


Scheduling of the annual accreditation review will be discussed with the laboratories needing accreditation.


Table 1 is the list of items to be reviewed.


An oral close out on any deficiencies will be held with the testing personnel. Written notice will be sent within two months of the inspection. CML personnel will re-inspect if necessary after correction of any deficiencies.


A report showing the laboratory, the date accredited, and the expiration date will be issued by the Materials Testing Engineer.





A laboratory that does not meet the requirements of the IM is subject to elimination from the qualification program.


The CML and the District Materials Engineer will resolve disputes concerning calibration and correlation of equipment.




TABLE 1 - Laboratory Accreditation Checklist





Minimum Calib./Verif. Interval

Calib./Verif. Procedure

Tester Qualifications-Proper Iowa DOT certifications




Current Test Procedures




Current Calibration Procedures & Records




Documentation of correlation results and corrective actions taken for previous construction season










  12 months

Iowa 917-B



  12 months

Iowa 1501-A

Mechanical Shakers


  12 months

Iowa 1502-A

Marshall Compactor T-245


  12 months

Iowa 1504-A

Gyratory Compactor T-312


    6 months

Iowa 1522-A

Marshall Molds T-245


  12 months

Iowa 1523-A

Comp. Test Machine T-245


  12 months

Iowa 1505-A



    6 months

Iowa 1506-A

Thermometers - Test


    6 months

Iowa 1607-A

Thermometers - Ref.


  12 months

Iowa 1607-A

Timers T-201, T-202


    6 months

Iowa 1508-A

Sand Equivalent T-176


  12 months

Iowa 1509-A

Gyratory Compactor Molds T-312


  12 months

Iowa 1524-A

Vacuum Systems T-209


  12 months

Iowa 1510-A

Pycnometers T-228, T209


  12 months

Iowa 1618-A

Fine Aggregate Anularity T-304


  12 months

Iowa 1525-A

Dynamic Shear Rheometer T-315


    6 months

Iowa 1612-A

Balance Weights M-231


  12 months


Sample Splitters T-248


  12 months

(visual condition)