Materials Notebook: Materials Control
U.S. Department of Transportation
Federal Highway Administration
||Materials Control/Reduced Staffing
||APR 24 1985
||Chief, Construction and Maintenance Division
|Office of Highway Operations
||Regional Federal Highway Administrators
Regional Materials Engineers
Over the last several years, many State highway agencies have suffered budget constraints and personnel limitations or cutbacks, especially in the construction, inspection, and materials testing areas. At the same time, the level of highway funding and the number of highway construction projects have been increasing. These two factors require the more efficient use of available State personnel. Several ways to accomplish this have been discussed and/or tried experimentally by various agencies. Based on some observations from our materials reviews, we have identified three engineeringly sound and successful approaches to the problem. They are:
- Process control by the producer;
- materials testing by consultant technicians; and
- materials testing by independent laboratories.
In each of these approaches, two critical issues arise. They are technician qualification and laboratory accreditation.
Traditional State operation provided qualified technicians by in-house training and well defined supervisory relationships. However, where the inspecting, sampling, and testing technician is not a State employee, there is a need to establish and evaluate the qualifications of the technician performing the assigned duties.
The materials technician certification programs available and being used include:
The National Institute for Certification of Engineering Technologies (NICET) is the only nationally available program. The program provides for excellent training and examination in materials and materials testing in the areas of asphalt, concrete, and soils. The program is constantly monitored and updated by NICET.
Numerous State highway agencies (SHA's) have developed training information and certifications for both State and contractors' or consultants' technicians. Their programs vary from on-the-job training to classroom training. Certification is issued based on varying criteria which ranges from successful completion of a written exam and demonstrated testing efficiency to an oral interview with State engineers or senior technicians. Each program was developed informally based on State needs. Applicability from State-to-State is limited and implementation of another SHA's program may not give satisfactory assurance of qualification.
It is recommended that contractors'/consultants' technicians be required to be certified by the State prior to conducting testing on a project where this testing is required. Certification under the NICET program should be required by the State along with a State certification issued after a probation period on-the-job to ensure the technician's familiarity with State specifications, procedures, and standard forms. Recertifications should be required on a periodic basis such as every 2 years.
Traditionally, materials testing was done entirely with State furnished and/or State calibrated/checked equipment. Assurance as to the adequacy of the State's laboratories, equipment, and procedures to correctly test materials was provided by the regularly performed inspections of the headquarters laboratory equipment and procedures by the American Association of State Highway and Transportation Officials Reference Laboratory (AMRL) and the National Bureau of Standards (NBS) Cement and Concrete Reference Laboratory (CCRL). The AMRL program provides for inspection of the laboratory equipment and testing procedures for compliance to AASHTO standards in the areas of soils, aggregates, and bituminous materials. The CCRL inspections are concerned with the testing equipment and procedural compliance to the American Society for Testing and Materials Standards. In addition to these inspections, there is also a program for testing of comparison samples of materials. Most of the States have programs for performing similar inspections on their district or satellite field laboratories. However, under a changed operation a State may hire independent laboratories to perform some testing. Here again, the adequacy of the equipment and the correctness of the operator's procedures in these independent laboratories is a matter of concern.
The laboratory qualification/accreditation programs available and being used include:
The AMRL program, while once confined to inspecting only the States' central laboratories, has now expanded to provide inspection services for laboratory equipment and procedures to any requesting laboratory involved in the testing of soils, aggregates, and bituminous materials. The cost of inspecting private or independent laboratories will be based on the number and type of tests which the laboratory performs. It should be noted that the AMRL program is not an accreditation program and the inspection report cannot be used for advertisement purposes. The CCRL inspection program is also available to any laboratory on a fee basis.
Several other programs including the American Association for Laboratory Accreditation (AALA) and the American Council of Independent Laboratories, Incorporated (ACIL) are available but these programs currently consist of basic reviews of available equipment and personnel without the detailed inspections which we believe are necessary.
It is recommended that those States that find it necessary to utilize independent laboratories for testing materials for use in Federal-aid highway work inspect the laboratories in the same manner as they would their district or satellite laboratories or require that they be inspected by AMRL or CCRL as appropriate. The latter is the preferred procedure since the inspection teams are comprised of recognized experts in their fields which are confined to highway materials. The State should monitor the private or independent laboratory periodically to determine if there have been any changes in the personnel performing the tests or if any of the equipment has been changed or replaced.
Each of the three approaches identified above will be detailed and key elements identified and discussed in the following paragraphs. We believe each of these approaches can be used successfully to assure materials quality and control in situations where staff reductions are occurring.
Process Control by the Producer
State testing can be reduced provided sufficient testing for control is done by the producer. As producer control is established, especially in fixed site plants, acceptance testing frequencies may be able to be reduced. The two key elements in a successful producer process control approach are (1) the producer's development and compliance with an approved control plan, and (2) the agency's monitoring of that compliance.
A producer's control plan should include the following:
- A materials sampling and testing plan including tests and frequencies. The test results must be plotted on control charts.
- Documentation and retention of all information/certifications on incoming materials.
- Scheduled calibration and checking of testing equipment.
- Physical plant inspection schedule and documentation.
- Plant operator and tester qualifications. Testers should be certified under the NICET and by the State. The NICET certification should assure that the tester has a basic understanding of engineering principles and testing procedures, while State certification will assure knowledge of State specifications, procedures, and forms. State certification should include a probation period.
- Plant batcher/operator certificate of specification compliance with each shipment/load/batch of material going to State project.
The State monitoring of the producer's control should include:
- assignment of an engineer or senior level technician to monitor the producer's control plan compliance and material quality;
- provision for daily inspection and unannounced periodic inspections to extract acceptance samples, review documentation such as materials invoices/certificates, producer inspection reports, control charts, etc;
- provisions for plant inspection and approval prior to start-up and on a periodic (1 year) basis; and
- provisions for observation of the producer's sampling and testing, plant and testing equipment calibration, producer's inspection, etc., whenever possible.
A typical specification outlining these requirements is attached as Appendix A. This approach is effective in providing materials testing with a reduced number of State materials technicians.
Materials Testing by Consultant Technicians
Another approach to providing materials testing capabilities in the face of reduced State staff is by hiring outside technicians. The best approach provides for each State district to contract with a consultant to furnish qualified materials technicians, at plant or project sites within that district. The contract is best handled on a basic hourly rate for the technician's time (including consultant overhead, profit, etc.).
The consultant is responsible for training and development of the technicians prior to assignment on State projects. Technicians should be certified under the NICET program and by the State after a probationary on-the-job evaluation period and recertified as described earlier.
The State should provide an engineer or senior technician to monitor the production and testing operations on a periodic basis. Monitoring efforts should be frequent during the probationary period and any other time when problems are suspected. The contract must specify that the State has the authority and means to have the consultant remove a technician that is not performing the assigned tasks correctly.
Information and guidelines in developing a contract of this nature is described in FHPM 1-7-2, "Administration of Negotiated Contracts" and more specifically in superseded FHPM 6-1-2-2, "Engagement of Consultants for Engineering Services."
Materials Testing by Independent Laboratories
The third approach for providing materials testing is by contracting with independent laboratories. These laboratories will supply and maintain the necessary equipment and qualified technicians for conducting the testing for process and/or acceptance. These laboratories should be inspected by the State in the same manner as a State district or satellite laboratory or by AMRL/CCRL. Technicians should be State certified as described earlier.
A specific example of minimum requirements for testing laboratories is included in Appendix B.
Administration of this type agreement is generally more difficult than having a consultant merely provide technicians because of the numerous complexities and problems which occur during a project's life. The method of compensation should account for variations in testing frequencies. Agreement provisions should also provide for periodic State monitoring and unannounced inspections to assure satisfactory laboratory performance and materials quality and control.
The three approaches described can be effectively used for assuring materials quality and control testing. The first two described methods are preferred because of tighter State control of the personnel and the testing. It should be noted that all acceptance testing should be done by SHA personnel or personnel employed by the SHA and not the contractor/producer. If more information is needed, please contact the Geotechnical and Materials Branch (HMO-33, FTS 426-0436).
SIGNED P.E. CUNNINGHAM
P. E. Cunningham
SPECIFICATION FOR CONTRACTOR QUALITY CONTROL SYSTEM
This establishes minimum requirements and activities for a contractor quality control system. These requirements pertain to the inspections and tests necessary to substantiate material and product conformance to contract requirements and to all inspection and tests required by the contract.
- FUNCTIONS AND RESPONSIBILITIES
a. The State highway agency (SHA). The SHA will approve mix designs, plant inspections, and monitor control of the operations to assure conformity with the specifications.
At no time will the SHA's representatives issue instructions to the contractor or producer as to setting of dials, gauges, scales, and meters. However, the SHA's representatives may question and warn the contractor against the continuance of any operations or sequence of operations which will obviously not result in satisfactory compliance with specification requirements.
b. The Contractor. At the preconstruction conference, the contractor shall submit in writing his proposed quality control plan for approval of the SHA. The plan should contain the sampling, testing, inspection, and the anticipated-frequencies of each that the contractor expects to accomplish to maintain process control. A recommended series of sampling, testing, and inspecting activities are shown in Table 1 and Table 2.
RECOMMENDATIONS FOR A PRODUCER QUALITY
CONTROL PLAN FOR BITUMINOUS MIXTURES
- All Types of Plants
- Determine gradation of all incoming aggregates
- Inspect stockpiles for separation, contamination, segregation, etc.
- Cold Bins
- Calibrate the cold gate settings
- Observe operation of cold feed for uniformity
- Observe pyrometer for aggregate temperature control
- Observe efficiency of the burner (unburned fuel oil)
- Hot Bins
- Determine gradation of aggregates in each bin
- Determine theoretical combined grading
- Bituminous Mixture
- Determine percent bitumen
- Determine mix gradation
- Check mix temperature
- Batch Plants
- Batch Weights - Determine percent used and weight to be pulled from each bin to assure compliance with job-mix-formula
- Check mixing time
- Check operations of weigh bucket and scales
- Continuous Mix Plant
- Determine gate calibration chart for each bin
- Determine gate settings for each bin to assure compliance with the job-mix-formula
- Determine gallons per revolution or gallons per minute to assure compliance with the job-mix formula
- Mixer Plant
- Calibrate the cold feed and prepare a calibration chart for each cold gate
- Develop information for the synchronization of the aggregate feed and the bituminous material feed
- Determine aggregate moisture contents to make necessary corrections to dry weight.
RECOMMENDATIONS FOR PRODUCER QUALITY CONTROL
PLAN FOR PORTLAND CEMENT CONCRETE
- Incoming Materials
- Incoming cement certifications proper
- Cement storage proper
- Determine gradation of incoming aggregates and fineness modulus of fine aggregate
- Aggregates from acceptable sources
- Inspect stockpiles for separation, contamination, segregation, etc.
- Measuring Devices
- Scales calibrated/checked for accuracy and precision
- Flow meters calibrated/checked
- Moisture meter-check/verified by moisture testing
- Admixture dispensers functioning/calibrated
- Manufacturer's design details on hand
- Central mixer timing device operating satisfactorily
- Truck mixers equipped with properly functioning revolution counters, water gauges, etc.
- All mixers free of hardened concrete
- Mixers inspected weekly for proper functioning, wear, hardened concrete, etc.
- Mixing Concrete
- Batching sequence proper
- Mixing speed and/or time proper
- Concrete checked for uniformity, tested for specification compliance
The activities shown in Tables 1 and 2 are considered to be normal activities necessary to control the production at an acceptable quality level. It is recognized, however, that depending on the type of process or materials, some of the activities listed may not be necessary and in other cases, additional activities may be required. The frequency of these activities will also vary with the process and the materials. When the process varies from the defined process average and variability targets, the frequency of these activities will be increased until the proper conditions have been restored.
The contractor or producer shall plot and keep up-to-date control charts for all quality control sampling and testing.
The contractor shall be responsible for the formulation of all mix design. Contractor-furnished mix designs must be submitted to the SHA for approval, prior to their use. The contractor shall be responsible for the process control of all materials during handling, blending, mixing, and placing operations.
- QUALITY CONTROL SYSTEM
- General Requirements. The contractor shall furnish and maintain a quality control system that will provide reasonable assurance that all materials and products submitted to the SHA for acceptance conform to the contract requirements whether manufactured or processed by contractor or procured from suppliers or subcontractors. The contractor shall perform or have performed the inspection and tests required to substantiate product conformance to contract requirements and shall also perform or have performed all inspections and tests otherwise required by the contract. The contractor shall have a quality control technician, who has been certified by the SHA available at the asphalt plant at all times the contractor is producing mix for the SHA. The SHA certification is dependent on NICET certification and satisfactory on-the-job performance during a probationary period. The contractor's quality control procedures, inspection, and tests shall be documented and that information be available for review by the SHA throughout the life of the contract.
- Documentation. The contractor shall maintain adequate records of all inspections and tests. The records shall indicate the nature and number of tests made, the number and type of deficiencies found, the quantities approved and rejected, and the nature of corrective action taken as appropriate. The contractor's documentation procedures will be subject to the review and approval of the SHA prior to the start of the work and to compliance checks during the progress of the work. All charts and records documenting the contractor's quality control tests and inspections shall become the property of the SHA upon completion of the work.
- Charts and Forms. All conforming and nonconforming inspections and test results shall be recorded on approved forms and charts which shall be kept up to date and complete and shall be available at all times to the SHA during the performance of the work. Test properties for the various materials and mixtures shall be charted on forms which are in accordance with the applicable requirements of the SHA. A copy of each chart and form to be used by the contractor will be furnished by the SHA. The contractor will furnish his own supply of the charts and forms. The contractor or producer may design their own forms and charts; however, these must be approved by the engineer prior to their use.
- Corrective Actions. The contractor shall take prompt action to correct any errors; equipment malfunctions, process changes, or other assignable causes which have resulted in or could result in the submission of materials, products, and completed construction which do not conform to the requirements of the specifications. When it becomes evident to the SHA that the contractor is not controlling his process and is making no effort to take corrective actions, then the SHA will require that plant operations be ceased until such time as the contractor can demonstrate that he can and will control the process.
- Laboratories with Measuring and Testing Equipment. The contractor or producer shall furnish a fully equipped laboratory at the production site. This facility may be permanent or portable. The laboratory shall be furnished with the necessary testing equipment and supplies for performing process control sampling and testing as well as SHA acceptance sampling and testing. To assure accuracy, the testing equipment will be checked prior to start up and periodically as directed by the SHA in accordance with applicable standards.
- Sampling and Testing. Sampling and testing methods and procedures used by the contractor to determine quality conformance of the materials and products will be the same as those used by the SHA. Samples shall be taken in accordance with the contractor's approved procedures for random sampling. The contractor's quality control plan will include the taking of samples for other material characteristics on a random basis and the plotting of the test results on control charts.
- Alternative Procedures. Alternative sampling methods, procedures, and inspection equipment may be used by the contractor when such procedures and equipment provide, as a minimum, the quality assurance required by the contract documents. Prior to applying such alternative procedures, the contractor shall describe them in a written proposal and shall demonstrate for the approval of the SHA that their effectiveness is equal to or' better than the contract requirements. In case of dispute as to whether certain proposed procedures of the contractor provide equal assurance, the procedures stipulated in the contract documents shall apply.
- Nonconforming Materials. The contractor shall establish and maintain an effective and positive system for controlling nonconforming material, including procedures for identification, isolation, and disposition. Reclaiming or reworking nonconforming materials shall be in accordance with procedures acceptable to the SHA. ,he details of this system must be discussed at the preconstruction conference and become a part of the record of the conference.
- SHA Inspection at Subcontractor or Supplier Facilities. The SHA reserves the right to inspect materials not manufactured within the contractor's facility. This inspection shall not constitute acceptance nor shall it in any way replace the contractor's inspection or otherwise relieve the contractor of his responsibility to furnish an acceptable material or product. When inspection of the subcontractor's or supplier's product is performed by the SHA, such inspection shall not be used by the contractor as evidence of effective inspection of such subcontractor's or supplier's product.
Subcontracted or purchased materials shall be inspected by the contractor when received, as necessary, to assure conformance to contract requirements. The contractor shall report to the SHA any nonconformance found on SHA source-inspected material and shall require the supplier to take necessary corrective action.
MINIMUM REQUIREMENTS FOR MATERIALS TESTING LABORATORIES
To have assurance that independent materials testing laboratories are capable of achieving an acceptable level of results, it is necessary that certain minimum standards be established. The minimum requirements necessarily include criteria for personnel, equipment, and quality control procedures. The requirements apply to all construction acceptance testing and inspection including asphalt concrete and portland cement concrete mix design.
These requirements shall be applicable to all parties performing services associated with Federal-aid highway construction projects undertaken by the State highway agency (SHA).
To receive approval, the testing laboratory shall meet the latest requirements, applicable to the work for which is it to be engaged of ASTM Designation D-3666, "Evaluation of Inspection and Testing Agencies for Bituminous Paving Materials," E548, "Recommended Practice for Inspection and Testing Agencies for Concrete, Steel, and Bituminous Materials as Used in Construction," and E548, "Recommended Practice for Generic Criteria for Use in the Evaluation of testing and Inspection Agencies."
The testing laboratory shall have its laboratory equipment and procedures inspected at intervals not to exceed 2 years by a qualified national authority as evidence of its competence to perform the required tests and material designs. Acceptable national authority will include the AASHTO Materials Reference Laboratory (AMRL) and/or the Cement and Concrete Reference Laboratory (CCRL) as appropriate . In addition, testing machines and equipment must be calibrated annually or more frequently by impartial means using devices of accuracy traceable to the National Bureau of Standards.
In fields other than those covered by the referenced ASTM Standards, the testing laboratory shall accept only those assignments which it is able to perform competently by use of its own personnel and equipment. Any work to be subcontracted must be to laboratories meeting the same criteria.
The testing laboratory shall have demonstrated its competence in the applicable fields for a period of not less than 3 years.
The inspection and testing services of the testing laboratory shall be under the direction of a full-time employee registered as a professional engineer in the State. He shall have a minimum of 5 years of professional engineering experience in inspection and testing of the specific materials and construction which he directs.