The HMA Proficiency Program is part of the Independent Assurance Program described in IM 205. The HMA Proficiency Program provides participating laboratories with a means to:
· Check both the instrument and the operator under actual testing conditions.
· Compare individual test results with the average of a large body of results so that corrective action may be taken where wide discrepancies occur.
· Evaluate the quality of test results, thereby reducing the risk of dispute due to testing errors.
Each accredited and qualified Laboratory and certified staff shall establish and maintain their proficiency by following program described herein.
A project approach for independent assurance may be used for RCE, county, city, and consultant laboratories.
WITNESSING FOR IAP
The District Materials Offices are responsible for witnessing the HMA mix sampling, and splitting; the binder sampling; and the cold feed aggregate sampling and quartering (if used as the acceptance method for gradation). When using either the project approach or the system approach, document with a report (A fillable report form is at http://www.iowadot.gov/Construction_Materials/assurance/IAP_Worksheet.pdf).
· Who was checked
· When
· Where including project number
· What activity was checked
· Comments on observations
· The name of the person doing the IA
The Central Materials Laboratory will prepare and send out proficiency samples during the construction season (April through September). The samples and tests for laboratories will be as follows:
A. District Laboratories
1. Asphalt Binder
a. G*/Sin Delta
2. HMA Mix
a. Gmb Laboratory Density
b. Gmm Maximum Specific Gravity
c. % Binder, Ignition Oven
d. Gradation, Ignition Oven
3. Combined Aggregate
a. Gradation
b. Gsa Apparent Specific Gravity (every other sample)
c. Gsb Bulk Specific Gravity (every other sample)
d. Percent Absorption (every other sample)
e. Fine Aggregate Angularity (every other sample)
B. HMA Laboratories
1. HMA Mix
a. Gmb Laboratory Density
b. Gmm Maximum Specific Gravity
2. Combined aggregate
a. Gradation
C. Aggregate Laboratories
1. Gradation
A. District Laboratories
Each District Laboratory will receive a set of proficiency samples monthly April through September. The samples will be tested and the results reported within 14 calendar days of receipt
B. Contractor HMA laboratories
Each active certified HMA technician performing quality control testing for state or local federal aid projects will pick-up proficiency samples in April from the closest District Laboratory. The samples will be tested and the results reported to the Central Materials Laboratory by May 15 using the spreadsheet form at: https://iowadot.gov/construction_materials/assurance/iaPform13.xlsm
For active certified technicians that do not obtain a proficiency sample in April, they must contact the District Laboratory in the District where they will be working and obtain and test a proficiency sample prior to the start of paving. Results will be compared to the District Laboratory results for that month.
TEST RESULT ANALYSIS
Test results from the proficiency samples will be analyzed using the current AASHTO Material Reference Laboratory (AMRL) procedure. The analysis compares the results from each participant and each District and Central Laboratory to the overall mean. Test results will also be compared to the Central Materials Laboratory results.
Any test result that is 3.0 standard deviations or greater from the mean will be considered failing. Two consecutive proficiency sample results that are 2.0 standard deviations or greater from the mean will be considered failing.
In the event of a small data set or large or small variation within a data set, the individual results will be compared with the Central Laboratory results. IM 216 will be used to compare the results. Proficiency test results beyond the tolerance will be considered failing.
Investigation of Failing Test Results
The technician with failing test results shall review the calculation, test procedures, and perform a calibration if warranted. When there are two or more consecutive failing results, the Central Materials Laboratory or the District Material Engineer will contact the technician and arrange to conduct an evaluation of the procedures and equipment to correct any deficiencies. Three consecutive failing results by a technician will constitute unsatisfactory performance as defined in IM 213 and become a part of their permanent file.
If an active certified HMA technician fails to obtain and test a proficiency sample, the District Materials Engineer will conduct an investigation and if warranted issue an unsatisfactory performance notice.
If an active DOT certified HMA technician fails to test and report a proficiency sample by deadline, the District Materials Engineer will be notified to conduct an investigation and if warranted issue an unsatisfactory performance notice.