|Cement and Concrete Reference Laboratory |
Promoting Quality in Laboratory Testing
by James H. Pielert
In 1929, Committee C01 created an organization in concert with NBS, PCA, and other funders that has benefited the cement and concrete industry to this day. Long time Cement and Concrete Reference Laboratory manager Jim Pielert describes the programs of this indispensable lab.
The Cement and Concrete Reference Laboratory (CCRL) has been described as an outstanding example of government-industry cooperation. Its history goes back to 1929, when the quality of hydraulic cement being supplied to U.S. government projects was a concern. (1,2) A number of organizations including ASTM, the National Bureau of Standards (now the National Institute of Standards and Technology (NIST)), and the Portland Cement Association (PCA) collaborated in the formation of the Cement Reference Laboratory (CRL) as a Research Associateship Program at NIST in 1929. In 1960, CRLs scope was expanded to include hydraulic cement concrete and concrete aggregates and its name was changed to the Cement and Concrete Reference Laboratory. Later changes to CCRLs scope include the addition of blended cement, pozzolans, masonry mortar, and concrete masonry unit proficiency samples, and the inspection of laboratories testing pozzolans.
CCRL and the AASHTO Materials Reference Laboratory (AMRL) constitute the Construction Materials Reference Laboratories (CMRL) located in the Materials and Construction Research Division of the NIST Building and Fire Research Laboratory. (1, 3) CCRL is sponsored by ASTM, and AMRL by the American Association of State Highway and Transportation Officials (AASHTOsee sidebar). Both reference laboratories currently operate at NIST as Research Associateship Programs under memoranda of agreement with the sponsors signed in 1999. A joint subcommittee of ASTM Committees C01 on Cement and C09 on Concrete and Concrete Aggregates provides technical oversight of CCRL. ASTM is responsible for management of the business affairs of CCRL.
CCRL operates three programs that promote the quality of laboratory testing of some major construction materials: Laboratory Inspection Program, Proficiency Sample Program, and Research Program.
Laboratory Inspection Program
The CCRL Laboratory Inspection Program has more than 900 participating laboratories (Figure 1). Inspections are conducted on a tour basis covering all laboratories in the United States, Canada, and Mexico wishing to participate; each tour lasts approximately 30 months. The CCRL inspection service is available on a fee basis to laboratories that conduct ASTM tests on hydraulic cement, hydraulic cement concrete, aggregates, reinforcing steel, and pozzolans. CCRL is unique in the manner in which inspections are carried out. Each inspection includes an on-site visit to the laboratory to a) evaluate its test equipment for compliance with the ASTM standards for the tests for which it is used, b) witness test procedures being carried out by a laboratory technician, and c) evaluate the laboratorys quality system. CCRL laboratory inspectors use detailed worksheets based on current ASTM standards to evaluate every test method selected by the laboratory for evaluation (Figure 2). Inspection equipment, traceable to NISTincluding load cells, balances, standard masses, thermometers, and micrometersis used in evaluating the laboratorys equipment. Reviews of the laboratorys quality system are based on ASTM C 1222, Practice for Evaluation of Laboratories Testing Hydraulic Cement, and ASTM C 1077, Practice for Laboratories Testing Concrete and Concrete Aggregates for Use in Construction and Criteria for Laboratory Evaluation. Laboratory staff receive an oral report and a preliminary written report at the conclusion of the inspection, followed by a more comprehensive written report prepared after the laboratory inspector returns to CCRL. These reports are strictly confidential unless a laboratory requests other distributions in writing.
Proficiency Sample Program
The CCRL Proficiency Sample Program provides participating laboratories with the opportunity to compare their results with those from other laboratories by testing samples of the same material. The proficiency samples for distribution are prepared in a facility at NIST (Figure 3). CCRL obtains and homogenizes representative material, and packages and ships the samples to participating laboratories with instructions for testing. The statistical analysis performed on test results returned by the laboratories results in the generation of a summary report of findings which is sent to participating laboratories.
Proficiency samples currently distributed by CCRL (and the number of participating laboratories) are: Portland cement (270), blended cement (82) masonry cement (83), hydraulic cement concrete (835), pozzolans (85), concrete masonry units (72), and masonry mortar (44). Figure 4 shows the growth in laboratory participation in the Portland Cement Concrete Program. Currently, more than 1,000 laboratories participate in one or more of CCRLs proficiency sample programs, including 72 laboratories in 25 countries outside the United States.
The memorandum of agreement with NIST signed by ASTM and AASHTO in 1999 required CCRL and AMRL to develop research activities that will enhance their programs and have programmatic relationships to NIST research programs. The research program developed meets this requirement. CCRL contributes to the development of standards, and provides staff and other assistance to BFRL researchers in areas of common interest.
CCRL contributes to the development of ASTM standards in several ways. These include providing an interface for exchange of information between ASTM standards developers and laboratory users of the standards. CCRL routinely provides data collected in the Laboratory Inspection and Proficiency Sample Programs to ASTM committees. Interlaboratory test data collected in the Proficiency Sample Program are used in the preparation of precision statements required in ASTM test method standards. ASTM C 670, Practice for Preparing Precision and Bias Statements for Test Methods of Construction Materials, includes a procedure for using CCRL data for this purpose. CCRL prepares a summary of findings after each inspection tour showing the extent of laboratory conformance to the requirements of ASTM test methods and specifications. This information suggests where laboratories are having difficulties using the standards, and helps ASTM committees identify needs for improvement of standards.
When requested to do so, CCRL also conducts special interlaboratory studies for ASTM Committees C01 and C09 to collect data needed for precision statements and to evaluate proposed changes to standards. For example, CCRL assisted the BFRL Materials and Construction Research Division and ASTM C01.25 Task Group on Particle Size Distribution (PSD) in the development of a new standard for PSD using automated equipment, and in generating a PSD curve for NIST Standard Reference Material 114 (Portland Cement Fineness Standard). CCRL assisted in identifying 42 laboratories willing to participate in the study, and prepared and distributed the samples for testing.
In other recent work, CCRL helped ASTM Subcommittee C01.30 on Time of Set evaluate the current procedure for determining final time of setting with the objective of preparing a new procedure for Committee C01 balloting. CCRL, in conjunction with the distribution of portland cement samples 143 and 144, sent additional material to 111 laboratories along with instructions for additional testing. The resulting data were considered by the subcommittee at its June 2002 meeting and will be used to prepare a revision to the Vicat final time-of-setting determination that reduces testing variability.
The CCRL Research Program also supports the Virtual Cement and Concrete Testing Laboratory (VCCTL) project in the BFRL Materials and Construction Research Division. (4) The project began in 1999 and a NIST-led VCCTL consortium was formed in November 2001. The consortium consists of three NIST laboratories and eight industrial members. Its overall goals are to develop a virtual testing system to reduce the need for physical testing of cement and concrete, and to expedite the research and development process. CCRLs Portland Cement Proficiency Samples are valuable for research conducted in the VCCTL. After their physical and chemical properties have been determined by the ASTM tests in the CCRL Proficiency Sample Program, the samples are subjected to additional characterization in the VCCTL Microstructure Laboratory using X-Ray diffraction, scanning electron microscopy, and X-Ray microanalysis. CMRL staff participate in the conduct of these analyses (Figure 5). In this way, a database on well-characterized cements is being assembled for use in VCCTL research and other purposes. For example, CCRL Cements 135 and 136 have been used to calibrate and validate the 3-D hydration and microstructure development model (CEMHYD3D) developed by the VCCTL. (5)
Users of CCRL Programs
The users of CCRL programs include materials producers, government agencies, and accrediting bodies, in addition to testing laboratories, standards developers, and researchers already discussed. The quality control laboratories in most cement plants in the United States choose to be inspected by CCRL. Several state agencies, including the California Division of the State Architect and the State of Massachusetts Building Code Commission, require laboratories doing ASTM standard testing of cement and concrete in their jurisdiction to be inspected by CCRL. While CCRL does not accredit or certify laboratories, several accrediting bodies rely on the CCRL and require that laboratories they accredit participate in the CCRL Laboratory Inspection and Proficiency Sample Programs. Participants in the Association of State Highway and Transportation Officials (AASHTO) Accreditation Program (AAP), (6) the American Association for Laboratory Accreditation (A2LA), and the National Voluntary Laboratory Accreditation Program (NVLAP) are required to participate in the appropriate CCRL Proficiency Sample Programs. AAP requires laboratories to participate in the CCRL Laboratory Inspection Program and NVLAP permits participation as an alternative to peer assessment. As of July 1, 2002, 758 laboratories were accredited by AAP, including 450 Portland cement and concrete laboratories.
Issues Affecting CCRL in the Future
Advances in the testing and prediction of performance of cement and concrete will be aided by CCRL programs and will lead to continuing improvement in the way CCRL evaluates laboratory performance. For example, the adoption of virtual laboratory testing concepts, such as those being developed in the VCCTL, and the movement toward performance and materials-science based standards, will likely lead to more reliance on analytical modeling and sophisticated materials characterization, but less on long-term testing. Laboratory equipment and facilities will become more automated and sophisticated, and require fewer, but better-trained, technicians. CCRL will play a role in facilitating improved testing. It is relevant to the future of CCRL that, almost certainly, more reliance will be placed on the use of accredited laboratories, as governmental agencies are required to implement staffing cutbacks. Also, as new cement-related construction materials are introduced, it is expected that services similar to those that CCRL now provides will be needed for the new materials. And finally, the movement toward design, build, maintain, and warranty contracting will require that materials properties be determined in a more accurate and consistent manner. Responding to these developments will pose serious challenges to CCRL, but it will face them confidently, as it has faced previous challenges during its 73-year history.
CCRL, which was established over 70 years ago in response to concern about the quality of Portland cement supplied to the U.S. government, continues to be a valuable resource in promoting and assuring the quality of laboratory testing of construction materials. It provides an example of how federal, state and local governments; standards developers; and industry can cooperate effectively with the common goal of improving the quality of the testing that is essential to the assurance of quality of construction. The value of CCRL programs is evidenced by the increasing number of laboratories participating in its Laboratory Inspection and Proficiency Sample Programs, and the dependence of laboratory accrediting bodies on these programs. CCRL research efforts, planned in conjunction with NIST, support the ASTM standards development process and, simultaneously, contribute to NIST research that should lead to further improvement in standards. //
(1) Pielert, James H., Construction Materials Reference Laboratories at NIST, ASTMStandardization News, ASTM, West Conshohocken, Pa., December 1989, pages 40-44.
(2) Promoting Quality in Laboratory Testing, Concrete Technology Today, Portland Cement Association, Vol. 14/Number 2, July 1993, pages 3-5.
(3) Pielert, J.H. and Spellerberg, P.A., AASHTO Materials Reference Laboratory Thirty Years of Service to the Transportation Community, TR News, Number 183, Transportation Research Board, Washington, D.C., March-April 1996, pages 22-28.
(4) Bentz, D.P., Editor, The Virtual Cement and Concrete Testing Laboratory Consortium Annual Report 2001, NISTIR 6840, Gaithersburg, Md., December 2001.
(5) Bentz, D.P., Feng, X., Haecker, C.J., and Stutzman, P.E., Analysis of CCRL Proficiency Cements 135 and 136 Using CEMHYD3D, NISTIR 6545, Gaithersburg, Md., August 2000.
(6) Procedures Manual AASHTO Accreditation Program, AASHTO, Washington, D.C., February 2002.
Copyright 2002, ASTM