A staff engineer reports on pre-assessment audits for the NPCA Plant Certification Program.
Quality has everything to do with high expectations, whether in the precast concrete industry or in the world of sports. Before British miler Roger Bannister ran a 4-minute mile in 1954, the world’s best runners believed that it was impossible for a human to run that fast. But once athletes believed it was attainable, they also began running the mile under 4 minutes.
What changed? People changed their beliefs about what standard was attainable. Setting high but attainable standards for the precast concrete industry is what NPCA’s Plant Certification Program is all about. And quality control is all about being the best in your field.
A typical pre-assessment plant audit
In the past four to five years that I have been involved with NPCA’s Plant Certification Program, there have been many changes. The “NPCA Quality Control Manual for Precast and Prestressed Concrete Plants” has been through numerous revisions – including the addition of new language, new quality control procedures, and new sections addressing prestressed concrete and precast architectural products. NPCA’s certification program has seen a vast expansion in the number of plants participating and in the number of states requiring the certification program. The “NPCA Consultation Program” title has changed to the current “NPCA Pre-Assessment Audit Program.”
During an NPCA Plant Pre-Assessment Audit Program, an NPCA Technical Services engineer spends an entire day or more with the plant personnel to ensure they have a firm
grasp on the requirements of NPCA QC Manual. This pre-assessment is a precursor exercise to a precast concrete facility’s initial certification inspection. The Technical Services engineer sits down with plant staff to meticulously go through documentation and records, and spends hours on the plant production floor ensuring all processes and quality control measures performed meet the requirements of the NPCA QC Manual. It is during this visit that the Technical Services engineer points out potential deficiencies and provides staff with possible resolutions in preparation for the initial certification inspection.
I have performed nearly 50 plant pre-assessment audits in North American and Puerto Rico. While I have found many positive consistencies among facilities entering into the plant certification program, I have also seen the other end of the spectrum – the quality control deficiencies – that are the subject of this article. The intent here is to share the more common problems encountered during a typical pre-assessment plant tour. The deficiencies listed in this four-part series relate to all six chapters of the NPCA QC Manual. In this article, I describe five common deficiencies. Watch for upcoming issues of Precast Inc. for the continuation of this series.
1. Incomplete plant-specific QC Manual
A detail-oriented, all-encompassing plant-specific Quality Control manual that meets or exceeds the requirements in Section 1.1.2 of the NPCA QC Manual is about as rare to come by as an Indianapolis Colts’ touchdown this past season. Like the Colts offense, an initial read of the manual may look promising, but once you reach the conclusion, the result is the same: incomplete. A solid, plant-specific QC Manual is one of the first items inspected, and this manual plays a vital role in the guidance of quality control procedures set forth by the plant.
The plant-specific QC Manual serves to: outline production and QC policies and procedures that are unique to the plant’s day-to-day operations; set limits and ranges for quality of the products manufactured; and reinforce the day-to-day QC measures and checks that plant personnel must adhere to in order for a certain level of quality to be achieved. The majority of plants will have a good start on a plant-specific quality control manual, but will not outline, in detail, all production and QC policies and procedures as required in Section 1.1.2 in the NPCA QC Manual (17 separate divisions). A plant-specific QC Manual should be frequently revisited and reviewed with the intent of continually improving operations and quality. Just remember: Say what you do, do what you say, and be able to prove it with the appropriate level of documentation.
2. Unqualified backup inspector
Plant QC inspectors and assigned backup inspectors must complete the minimum training requirements as set forth in Section 1.1.3 in the NPCA QC Manual, which states that the main QC inspector and the backup QC inspector will have completed and passed the NPCA Production and Quality School (PQS) and will also be American Concrete Institute (ACI) Concrete Field Testing Technician-Grade I certified. Plants generally have the main QC inspector trained and certified in ACI and PQS, but often the backup is noncompliant with one or more of the training requirements.
Requiring both the main QC inspector and the backup QC inspector to be trained in both fields is a newer stipulation in the NPCA Plant Certification Program, as it was implemented at the beginning of 2011. This requirement educates both the inspector and the backup inspector on how to properly perform concrete tests and also serves to refresh inspectors on proper concrete practices and procedures. Whether overlooked or misread, this training omission can account for a total of six lost points in the grading schedule – which can be a major detriment to the plant’s overall score.
3. Failure to meet aggregate testing requirements
“Coarse aggregates, fine aggregates and lightweight aggregates, oh my!” Like Dorothy and her “lions and tigers and bears” in the Wizard of Oz, plant staff tends to be understandably daunted by all the required documentation and certifications required for aggregates used in mix designs. Section 2.1.2 in the NPCA QC Manual clearly outlines all the required testing and conformance requirements for any type of aggregate used, although with a cursory glance, a plant could overlook certain requisites.
If the plant is dealing with strictly fine and coarse aggregates, then the aggregates must adhere to ASTM C33, “Standard Specification for Concrete Aggregates.” If the plant also uses lightweight aggregates, the aggregates should adhere to ASTM C330, “Standard Specification for Lightweight Aggregates for Structural Concrete.” For aggregates conforming to ASTM C33, a letter of conformance or testing records is required annually to indicate compliance (and therefore are nonreactive and stable). If the plant uses lightweight aggregates, then it will need to obtain an annual letter of conformance or testing records stating that the aggregates meet ASTM C330.
If the plant mix contains fine and coarse aggregates (ASTM C33), the plant must obtain gradation tests once for every 1,500 cu yd of fine aggregates and once for every 2,000 cu yd of coarse aggregates used, as per ASTM C136, “Standard Test Method of Sieve Analysis of Fine and Coarse Aggregates,” or once per month, whichever occurs first. If the plant is dealing with lightweight aggregates (ASTM C330), then these must be tested for gradation and unit weight initially and for each 200 cu yd of lightweight aggregate supplied, or once a month, whichever occurs first.
In addition to ASTM C33, ASTM C330 (if applicable) and ASTM C136, aggregates must also be tested once per year to ensure that they are nonreactive with respect to alkali silica reactivity (ASR). Compliance can be a letter of conformance or testing according to ASTM 1260 or ASTM C1293, or a letter from the Department of Transportation indicating that the aggregate is DOT approved.1
There are numerous conformance and testing records to keep track of in this section of the Manual, and if the plant’s QC inspector does not manage data closely, one or more of these records could be lost. Typically, we find the required frequency of the aggregate gradation testing is not achieved, resulting in a deficiency for this section.
4. Homemade lifting devices/apparatuses that are not load-rated
Spreader bars, spreader beams, lift bars, slings and hooks: all useful lifting devices/apparatuses, right? And these devices are almost always properly load-rated and marked for their rated working-load limit, right? Unfortunately, this is not the case. Many precasters have skilled workers and tradesmen at their disposal, who for the most part have previous welding or metalworking experience. This skill is beneficial in the sense that tradesmen can construct a simple yet useful lifting device or apparatus to meet the needs of the plant or to solve a unique situation when transporting a product. The QC issue that comes into play when a plant uses these homemade lifting devices is that plants do not typically verify the capacity or have an adequate factor of safety (FS) for lifting and handling addressed, as required in Section 2.3.1 of the NPCA QC Manual.
All lifting devices, even the smallest device (commercial or homemade), must be verified for capacity and should have an adequate FS for lifting and handing products, taking into account the forces acting on the device, including form-release suction, impact and various positions of the product during handling. The capacity of the lifting device must be marked on the device or posted in the production area. All lifting devices and apparatuses must meet the OSHA requirements documented in the “Code of Federal Regulations” Title 29 CFR Part 1926 or ANSI A10.9, ASTM C857, ASTMC890 and ASTM C913, whichever takes precedence.2 A FS ≥ 4 is recommended for lifting devices, and FS ≥ 5 is recommended for lifting apparatuses (see “Lifting Apparatuses: Holding Up Standards” in the November-December 2011 issue of Precast Inc.).
Plants often construct a homemade lifting apparatus that is overdesigned for the product intended for lifting, yet they do not have the engineering or testing to verify this capacity. As a result, they will receive a deficiency for lack of documentation to prove that the device is, in fact, safe to use. Because these lifting devices bear the evidence of significant wear and tear, the rated working-load limit on the device or apparatus cannot always be clearly read. Without knowing the rated working load, the device may be used in an unsafe manner or for loads that exceed the lifting capacity.
5. Lack of documented maintenance on forms
Forms in use, forms out of use, forms stacked 10-high on the production floor, monolithic forms, bolt- and pin-together panel forms: forms, forms and more forms! Staff can easily become confused about the requirements outlined in Section 4.1.3 in the NPCA QC Manual, and therefore deficiencies for this category are rampant. The requirements state that all forms and forming equipment (including pallets, headers and truing rings) should be measured prior to initial use and not less than annually for dimensional conformance with applicable tolerances. Each form should have its own unique identification number in order to easily track and document measurements.
Precast facilities will typically state that a form is a solid, monolithic steel form that is immovable, or the dimensions on the final cured product are within tolerances outlined in the plant-specific QC Manual. Consequently, they do not realize the need to annually check and document all forms in use on the production floor. Wrong! While the form may still meet the dimensional tolerances, I often see bad seams or seals that cause leakage of cement paste into the form’s corners, leading to bug holes and/or honeycombing in the edges of the product. A routine form maintenance program to repair hinges, remove bulges and minimize seam leakage will result in improved product finish quality as well as reduced production costs; hence one of the good reasons for an annual documented maintenance program.
Plants also commonly ask about singular, smaller, bolt- or pin-together panel forms used for custom work, larger-faced products and wall panels. These singular, panel-type forms are bolted or pinned together to construct a larger form. Plant personnel routinely ask how they should manage the maintenance and documentation of these forms and whether they fall into Section 4.1.3 requirements, as they might have hundreds of these smaller panel forms. The answer to this question is yes: These forms must be inspected, but this should be performed during the pre-/post-pour inspections and on a day-to-day and use-to-use basis. Merely creating a unique ID and documenting each bolt- or pin-together panel form does not represent the intent of this section requirement. Plant personnel should inspect every bolt- or pin-together form before each use to ensure that they are indeed in proper working order, but as far as creating a unique labeling system for each panel, that is not what the requirement mandates.
1 ASTM C1260 is the “Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar Bar Method)” and ASTM C1293 is the “Standard Test Method for Determination of Length Change of Concrete Due to Alkali Silica Reaction.”
2 ANSI/ASSE A10.9, “Concrete and Masonry Work Safety Requirements”; ASTM C857, “Standard Practice for Minimum Structural Design Loading for Underground Precast Concrete Utility Structures”; ASTM C890, “Standard Practice for Minimum Structural Design Loading for Monolithic or Sectional Precast Concrete Water and Wastewater Structures”; and ASTM C913, “Standard Specification for Precast Concrete Water and Wastewater Structures.”