To assess or not to assess?

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By Mark Homer

It is a lot of work. It will take a lot of time and expense. But, AMRL accreditation can be a vital measurement of the accuracy of your asphalt testing laboratory.

What is accreditation?

It is a formal recognition of the competence of testing laboratories to perform specific tests on construction materials. The American Association of State Highway and Transportation Officials (AASHTO) Accreditation Program (AAP) is relatively young (established in 1988) and is open to all testing laboratories (public and private.) Of nearly 1,500 individual laboratories currently accredited through AAP, only about 200 are accredited for asphalt binder testing.

Who is AMRL?

AMRL (AASHTO Materials Reference Laboratory) was started in 1965 with a focus on quality. AMRL provides administrative coordination and technical support for AAP. This includes inspecting and accrediting binder laboratories.

AMRL manager Bob Lutz assures they are not government employees. They are AASHTO employees working as an independent third-party private company.

Before, AAP formal recognition didn’t exist, but AMRL and CCRL (Cement and Concrete Reference Laboratory) were collectively known as CMRL (Construction Materials Reference Laboratory) and conducted on-site assessments and coordinated proficiency sample programs.

Why get accredited?

Test results have more significance when source competency has been demonstrated. If you have a disagreement with a specifying agent or a customer, laboratory accreditation gives credibility to your technical claims. All state laboratories are accredited and their results would have greater credibility than a non-accredited laboratory in a dispute. An accredited laboratory is recommended when choosing a referee laboratory. Some specifying agencies require laboratories working on their project to obtain AMRL accreditation.

How to get a laboratory accredited?

A laboratory must first have a quality management system meeting AASHTO R18 requirements. Specific accreditation requirements are covered in the AAP Procedures Manual. Accredited binder laboratories must also receive regularly scheduled on-site assessments by AMRL and actively participate in the applicable proficiency sample programs. Any nonconformity noted in the most recent assessment report must be adequately resolved within 90 days of the report issuance. Laboratories with poor rating for proficiency sample testing are required to conduct a root cause analysis to determine the reason(s) for the low ratings.

How to find an accredited laboratory?

The AMRL website ( contains an electronic directory of accredited laboratories. Each listing shows name, address, contact information, accredited test methods and date of initial accreditation for each testing field. Users can search by city or state/country. This is the sole source for current accreditation information.

When a laboratory seeks asphalt binder accreditation, some of the major parts of the project may include:

  • Establish a budget and time schedule.
  • Write a quality manual – AASHTO R18 can serve as a guide. AMRL personnel are available for help, too.
  • Calibrate all measurement devices (calipers, meters etc.) and make them NIST (National Institute of Standards and Technology) traceable. Calibration shops specialize in this service.
  • Write calibration procedures for all instruments—describe how you calibrate each instrument, what equipment is used and frequency.
  • Calibrate all instruments with these devices. This is where you use portable measuring devices to calibrate instruments that can’t be moved. This makes large immobile instruments NIST traceable.
  • Verify all equipment meets dimensional or other specifications (per test procedure.) Often, brand new test equipment fails dimensional specifications. RTFO bottles and ductility molds occasionally are the wrong size. Thermometers often don’t read exactly correct temperatures. This exercise will help improve your lab’s accuracy if all or many pieces of equipment are the wrong size.
  • Perfect your laboratory testing technique. Many test results are sensitive to operator technique.
  • Start proficiency sample testing. This is one time you want to be average.
  • Schedule an on-site assessment. AMRL covers the country every 18-24 months but an out-of-sequence inspection is available for an extra fee.
  • Address any nonconformity from assessment within 90 days of report issuance. This is enough time if issues are dealt with promptly.
  • Keep it up—maintaining accreditation is as much work as the initial accreditation.

Accreditation makes a laboratory better in many ways. Technique is improved through regular training and review. Equipment is maintained and calibrated according to the requirements in the specifications. Proficiency samples give performance feedback and direction where review is needed. The experience can provide your laboratory employees with a higher level of confidence.

Mark Homer, P.E. is the manager of Ajax Asphalt Terminal in Troy, Michigan.