About CTTP Laboratory Certification

The laboratory certification program is a comprehensive program to qualify non-agency laboratory equipment being used in quality control testing efforts. This program involves two major components – a check of the equipment used for testing, and a review of the quality system being used by the laboratory. The requirements for the laboratory certification program follow the basic framework of that used by the AASHTO Accreditation Program, which are outlined in AASHTO R18. CTTP laboratory certifications are location-specific, with the exception of Limited Lab Certification.

The CTTP Laboratory Certification Program has been in existence since the year 2000. Since that time, the program has evolved to meet the needs of contractors, producers, and materials testing firms, as well as to satisfy the requirements of the Arkansas Department of Transportation (ARDOT) and the Federal Highway Administration (FHWA).

CTTP laboratory certification is available in the areas of Aggregate, Concrete, Hot Mix, and Soil. Certification is granted after all applicable requirements have been met, and is method-specific. Individual test methods included in a laboratory’s certification are listed on the certificates, and are also indicated on the CTTP website listing of certified laboratories.

Laboratories holding current accreditation or certification from a nationally recognized organization may apply for reciprocal certification at a reduced fee.

Limited laboratory certification is available to labs performing minimal test methods at a reduced fee. Specifically, limited certification is available for AASHTO T310 (Nuclear Density of Soils), and for AASHTO T152 (Air Content of Concrete by the Pressure Method).

How To Begin

The laboratory certification process begins with a laboratory enrollment. The Enrollment Form is available on the CTTP website (www.cttp.uark.edu). On this form, laboratory information must be provided, and the individual specifications desired for the certification must be selected. After the enrollment form has been submitted, a lab number is assigned, and a Laboratory Agreement must be completed and signed by the laboratory representative and the CTTP Director.

Next, an inspection date is scheduled and the laboratory is encouraged to prepare for the inspection by ensuring that all equipment needed is in place an in proper working order, has been calibrated and/or verified, and all laboratory procedures have been properly documented. A Quality Manual should also be prepared, which includes information regarding the organizational structure of the laboratory and company, staff, equipment, and procedures. The Quality Manual should follow the general outline of that given in AASHTO R18.


Laboratories will be assessed certification fees according to the scope of certification (see fee schedule). Payment must be received by CTTP prior to the expiration date. CTTP accepts payment in the form of credit card, check, or money order.

The Inspection

The laboratory inspection is performed by the Laboratory Certification Coordinator (or other designated representative). During the inspection, the laboratory manager (or designated representative) must be present. In addition, all equipment needed for performing the requested test methods must be present and in working order, and will be evaluated to verify that it is adequate for the stated test methods. Various items are randomly selected for verification (i.e., a check of oven temperatures, water bath temperatures, scale accuracy, or sieve size openings). Also, the Quality Manual is reviewed for accuracy and completeness. Any items noted as deficiencies are included in the inspection report, which is sent to the laboratory after the inspection visit.

Deficiencies and Corrections

In order to receive certification, the laboratory must make the necessary corrections to all noted deficiencies by providing the requested documentation to the CTTP Laboratory Certification Coordinator. New laboratories are allowed six months from the date of inspection to respond to the deficiencies, and are not added to the CTTP list of certified laboratories until all requirements have been satisfied and payment has been received. At that time, certificates are sent to the laboratory and certification details are added to the CTTP website. Renewing laboratories are allowed approximately three months to properly respond to deficiencies, provided all requirements are met prior to the laboratory expiration date. Certifications are valid for a period of two years, based on the date of initial inspection.


In order to provide adequate time for completion of the certification process, renewing laboratories are notified by email at least 4 months prior to their expiration date. Typically, a laboratory can be scheduled for inspection within 3 weeks of submitting the signed Laboratory Agreement. After the inspection has been completed, approximately two weeks are required for generating the laboratory inspection report, allowing a minimum of 60 days for correcting deficiencies. Corrections to deficiencies usually require one week for review, and additional corrections may be required. If the laboratory elects to delay an inspection visit, the time available for correcting deficiencies will be limited by the expiration date. Time extensions will not be granted.


If all requirements are not met prior to the expiration date, the laboratory will be suspended from the CTTP laboratory certification program. Suspended laboratories are not allowed to submit laboratory test results to ARDOT for quality control purposes. When a laboratory is suspended, ARDOT is notified and the laboratory is removed from the CTTP website. Once suspended, the laboratory will have a 3 month period to adequately satisfy the program requirements before being completely removed from the certification program. If a lab is removed from the CTTP program, it cannot be returned to the list of certified laboratories until the laboratory re-enrolls and the entire certification process has been completed.


If a laboratory does not wish to renew certification, written notice on company letterhead should be provided to CTTP. Cancelled laboratories will be removed from the CTTP website and ARDOT will be notified of the change.