lishing that production facilities of readymixed concrete, which includes plants anddelivery vehicles, comply with minimumindustry standards. It reflects and in manycases exceeds the requirements of standardspecifications for ready mixed concrete, suchas ASTM C 94 and AASHTO M 157 andthe Concrete Plant Standards of the Con-crete Plant Manufacturers Bureau, CPMB100. A certified plant is permitted to displayan NRMCA Certificate of Conformancethat assures the purchaser that the facility isphysically capable of furnishing good quali-ty concrete. Reference to compliance toASTM C 94, Specification for Ready MixedConcrete, appears in most project specifica-tions and producer delivery tickets. TheNRMCA program provides a means of veri-fying to the purchaser and the producer thatconcrete is being produced in accordancewith ASTM C 94.

No claim is made that certification ofplant facilities will assure delivery of highquality concrete. Properly operated equip-ment is only one of several factors involvedin concrete control, although a very essentialone. The presence of a Certificate of Confor-mance should, therefore, be accepted precise-ly for what it is — evidence that certaincapabilities exist. The existence of thosecapabilities will reduce the likelihood of defi-ciencies in quality when normal inspection isexercised within requirements of usual salesagreements or project contracts. NRMCAPlant Certification is required by several stateagencies for state projects, the U.S. ArmyCorps of Engineers, several local specifyingauthorities and by several design firms repre-senting owners of commercial structures andfacilities. It is referenced in industry stan-dards such as the ACI 318 Building Codefor Structural Concrete, ACI 301 Specifica-

tions for Structural Concrete and the AIAMasterSpec.

Table 1 provides a breakdown of the num-ber of currently certified plants by state andthe number of delivery vehicles certified.NRMCA estimates that there are approxi-mately 6000-7000 plants and 80,000 mixertrucks operating the U.S. The number of cer-tified plants represents a relatively small percentage of the total, primarily becausemany state highway agencies conduct theirown plant inspections to qualify them forstate work.

N RMCA’s Plant Certification programwas instituted, following approval byits board of directors, in 1966. At the

time the development of the certification pro-gram was partly in response to a series of con-crete failures that were damaging thereputation of concrete as a building material.A national joint committee representingAmerican Concrete Institute, American Insti-tute of Architects and the American Societyof Civil Engineers was established to outlinein detail the specific responsibilities of all the principals in concrete construction. Thecreation of the NRMCA certification pro-gram represented an industry-developed pro-gram providing a fair and equitable auditprocess that set forth the quality standard forconcrete production facilities.

As the industry evolves to performance-based specifications, it is anticipated that cer-tification of plants and personnel will be animportant part of establishing a company’scredentials in its ability to produce perfor-mance-based concrete.

What Does Plant CertificationAccomplish?

NRMCA certification of concrete pro-duction facilities provides a system for estab-

6 ı FALL 2006

Ready Mixed Concrete Plant Certification:

State Number State Number Certified Certified

AK 3 MT 2AL 152 NC 1AR 16 ND 2AZ 11 NE 22CA 164 NH 0CO 10 NJ 9CT 0 NM 10DC 7 NV 48DE 2 NY 3FL 32 OH 40GA 10 OK 4HI 5 OR 4IA 2 PA 10ID 8 PR 0IL 40 RI 0IN 38 SC 8KS 18 SD 0KY 9 TN 20LA 10 TX 206MA 20 UT 44MD 23 VA 45ME 8 VT 1MI 246 WA 82MN 2 WI 37MO 5 WV 1MS 12 WY 1

Foreign Locations 19Total Plants 1472Total Trucks 15,000

By Colin Lobo, PhD, Vice President of Engineering, NRMCA

Table 1. Number of NRMCAcertified plants by state

A Mark of Quality

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documenting the reasons and benefits of thevarious requirements in the Plant CertificationCheck List. The company benefits from athird-party audit that can impart new ideas forimprovement.

Cost Effective. Companies have consider-able potential for savings on ingredient materi-als waste by monitoring scale accuracy andbatching records, reduced product rejection andproduct liability claims, increased new andreturn business with purchasers who demandquality and reduced time dealing with alterna-tive undefined local inspections.

The commitment by a company to obtaincertification requires an investment of personneltime and money to ensure that the systems arein place and are maintained, and the cost for theinspection and certification. It allows the com-pany to budget for necessary quality processesand improvements. The costs, however, aremore than offset by the benefits provided.

The ProcessCertification may be obtained by any pro-

ducer of ready mixed concrete with the proce-dures and limitations addressed in the check listdocument. The check list represents the itemsthat need to be inspected for conformance andrepresents requirements of current industrystandards. Certification is issued only when thefacility complies with all the pertinent require-ments in the check list. Revisions to require-ments of check list and certification policies areballoted for approval by the NRMCA ResearchEngineering and Standards (RES) Committeeand are subsequently approved by the NRMCABoard of Directors.

The certification program requires concreteproduction facilities and delivery vehicles to beaudited in accordance with the check list by aprofessional engineer licensed in the state wherethe facility is located. The licensed engineermay be an employee of the company, with theconsideration that he would be very knowl-edgeable of concrete operations and productionand is responsible to his code of licensure.While the inspecting engineer can only corrob-orate conformance at the time of inspection,another important part of the process is for aresponsible company official to sign an agree-ment to maintain the facility in conformancefor the duration of the certification.

Certification is valid for a period of twoyears for production facilities. Delivery vehiclesmust be recertified on an annual basis. The cer-tification process provides an option for deliv-

ery vehicles to be inspected by company person-nel with a subsequent audit of their process bythe inspecting engineer. A certificate of confor-mance is issued to the production facility afterthe completed checklist is reviewed byNRMCA. Proof of certification, with an expira-tion date, is provided for producers to display on their delivery vehicles. A certificate of conformance indicates the following for the production facility:• Plant name, location and company operating it• Type of plant – truck mixing, shrink mixing

or central mixing• Batching capabilities – manual, partially auto-

matic, semi-automatic or automatic • Recording capabilities, if any, for one or more

of cementitious materials, aggregates, waterand chemical admixtures

• Restricted capabilities for producing concrete in cold weather

• Signature and seal of the inspecting engineer• Signature of the responsible company

official• Inspection and expiration dates

A sample certificate of conformance is indicated in Figure 1, on page 11.

The RequirementsThe Plant Certification Check List includes

five sections briefly described below:• Section 1 addresses material storage and

handling processes for cementitious materi-als, aggregates, water and admixtures. Thechecklist items include requirements forgood practice and some requirementsaddressed in ASTM C 94.

• Section 2 addresses batching equipmentincluding scales, weigh batchers, volumetricbatching devices for water, and dispensers forliquid admixtures. It includes requirementsfor verifying accuracy of plant batching,defines batching systems and providesrequirements for batch recording devices.

• Section 3 is applicable to plants with a plantmixer. The section defines requirements for aplant to conform to a central mixing orshrink mixing operation. To qualify as a cen-tral mixing operation, the plant mixer needsto be visually inspected or evaluated by per-forming mixing uniformity tests.

• Section 4 addresses the requirements of aticketing system. This is required for a readymixed plant to conform to the certification.The reporting requirements on delivery tick-ets are the same as the mandatory reportingrequirements of ASTM C 94.

Another important part of a quality processis a company established quality plan forprocess control to assure quality and uniformconcrete. This is not implicitly addressed bythe NRMCA plant certification program. It isoften a part of a materials inspection programby state highway agencies in several states.

Companies choose to certify their produc-tion facilities because: 1) It is part of a qualityplan endorsed by management; 2) They wantto market their company against their com-petitors; and 3) Specifications require it. Themore common reason is number 3.

The Benefits of CertificationQuality Assurance. The purchaser of ready

mixed concrete is assured concrete is beingobtained from a quality focused company. Forlarger project specifications, the NRMCA cer-tification provides a means of verifying thatproduction of ready mixed concrete conformsto industry standards such as ASTM C 94.

Clear Expectations. The NRMCA plantcertification program provides a clear outlineand expectations to the owner of the plant, thespecifying authority and the inspecting engi-neer of the minimum standards for concreteproduction facilities. Since the program isdeveloped by industry members, the require-ments are considered fair and achievable. Plantowners can plan to ensure that all necessaryplant and truck components and productionprocesses are in place prior to an inspection.

Quality Focus. Certification provides ameans for identifying best practices for materi-als management, batching process and formonitoring production processes for optimumquality. The certification offers a discipline formanagement and production employees toensure scale and batching accuracy on definedperiods for all measuring devices with a goal toproduce and deliver uniform concrete. Thisallows for non-conforming product to be iden-tified and corrected before it is delivered to thecustomer.

Benchmarks for Efficiency. It provides fora means for companies to measure andimprove their production efficiency whilemaintaining quality. Benchmarks mightinclude quantifying material inventory, batch-ing accuracy, product performance consistencyand productivity targets.

Personnel Training. The certification pro-vides one part of a quality system that allowsplant managers an important tool to train pro-duction and quality control employees by

CONCRETE in focus ı 9

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plant and truck certification program to ensureit conforms to revisions of the referenced stan-dards. Since it represents a minimum industrystandard, the program serves to raise the bar forthe industry so all companies are operating atan equal level. Revisions are being considered toaddress the use of new material technologiesand production processes. Items that are beingconsidered for revision include achievablebatching tolerances, evolving control systemsand data recordation, cold weather operations,consistent procedures for calibration of scalesand volumetric measuring devices.

Another important initiative currentlyunderway is the development of a guide forplant inspections that will provide additionaldetails and information to both plant inspect-ing engineers and company production andquality control personnel. It is anticipated thatthe RES Committee will make this requiredreading for potential “NRMCA-approved”inspectors.

As a condition for adopting the NRMCAprogram, the state highway agency of SouthCarolina required the Carolinas Ready MixedAssociation to conduct a training program forplant inspectors. NRMCA facilitated a one-day

• Section 5 deals with the inspection of thedelivery fleet, which may be truck mixers,agitators or non-agitating units. Inspectionand certification of the delivery fleet is arequirement of the certification programsince it is part of the production and deliv-ery process. At least 90 percent of the fleetoperating from the plant must be acceptableto qualify for certification of the productionfacility. Delivery fleet can be inspected bythe company with an audit by the inspectingengineer or the complete fleet can beinspected by the inspecting engineer.

The Future of Plant CertificationAs evidenced by the increasing quality focus

and demands by users of concrete, certificationprograms are only going to see increased use.The push toward performance specificationswill support this and other certification pro-grams. While state highway agencies tradition-ally have inspected concrete productionfacilities, constrained resources are makingthem consider adopting national certificationprograms such as the NRMCA program.

The NRMCA RES Committee continuallymonitors the requirements of the NRMCA

CONCRETE in focus ı 11

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training program with a plant visit and anexamination to qualify inspectors in the state.The requirement for a licensed engineer stillexists in order to establish the credibility of theprogram. ■

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Figure 1. Example of a NRMCACertificate of Conformance

Information on details of the NRMCA cer-tification program for concrete production facil-ities and a copy of the Plant Certification CheckList are posted on the NRMCA website atwww.nrmca.org.