Ensuring the quality of construction is an important responsibility for local agencies; it’s how we assure the public that the elements of roadways, curbs, sidewalks, and such, whether we construct them or have contractors do so, will be durable and perform to reasonable expectations. In short, it is part of how we ensure the public got their money’s worth. Quality control and quality assurance (QA/QC) play an important role in that responsibility.
Let’s be honest; many of us have concrete sidewalks that are prematurely scaled or cracked, asphalt pavements that develop early potholes or other distresses, stormwater inlets that have settled, or concrete curbing that has crumbled early in its life. These elements are intended to have service lives of decades, not a year or two. So what happened? Well, too often the answer is a lack of construction quality or materials quality. And, before you roll your eyes and go on a convenient rant about unscrupulous contractors, recognize that you and your local agency dictate the terms of construction so if the project was poor, some of that is on your hands, too. Working appropriate quality assurance and quality control into your job specifications and executing them properly (even if the work is carried out internally) is a step towards keeping everyone targeted on a quality outcome.
Now, before someone starts carrying on about how concrete sidewalks, curbs, and roadways are destroyed by salt application during winter maintenance, let’s be clear. Properly prepared and constructed concrete should be able to withstand reasonable applications of chlorides. If you are unsure of what that means, look for our next offering of Concrete Best Construction Practices, a half-day training workshop intended for those newer to concrete construction. If, however, you are applying higher levels of salts than necessary, stop it; attend our next offering of Winter Maintenance; Snow and Ice Control training workshop. And, while we’re shamelessly plugging our training, put the Asphalt Best Construction Practices workshop on your list also. The best way to hear about these is to be on our distribution list, so use this link to get on it.
Quality control and quality assurance are two separate things and some of us like to be very, very pedantic about the definition of terms. In fairness, it is important to understand the difference, but we won’t get overly excited about it here. The greater takeaway will be that, as local agencies, we can and should actively ensure that quality of the constructed product is what we bargained for.
Alright then, what’s the difference? The Federal Highway Administration’s (FHWA) Transportation Construction Quality Assurance Reference Manual defines quality control (QC) as “The system used by a contractor party to monitor, assess, and adjust their production or placement processes to ensure that the final product will meet the specified level of quality.” Note that FHWA refers to a “system;” QC is more than just some tests done in the field, at batch plants, at quarries, or at pre-cast facilities. The next thing to note is that QC is the responsibility of the contractor. On the other hand, quality assurance (QA) is the responsibility of the project owner and/or its construction management consultants. A QA program consists of several core elements: establishing and/or approving contractor QC systems, independent assurance (IA), dispute resolution, personnel qualification, and laboratory accreditation/qualification.
As described by FHWA in their Optimal Procedures for Quality Assurance Specifications, the purpose of the contractor’s QC system, “is to measure those quality characteristics and to inspect those activities that impact the production at a time when corrective action can be taken to prevent appreciable nonconforming material from being incorporated into the project. The QC efforts should also be able to quickly identify that nonconforming material is being made. These purposes should serve as a guide to the decisions used in establishing the requirements and determining the quality characteristics to measure,” (emphasis added).
For example, employing experienced/qualified/certified personnel for appropriate job tasks, providing sources of materials in advance of the work, concrete slump tests, control of concrete water/cement content, confirmation of asphalt tack application rates, and asphalt density tests are some of the ways we can better ensure the completed project will be of the quality we specified. And while these are the contractor’s responsibility, the owner or owner’s representative can concurrently perform some of these same tests as part of the independent assurance (IA) that is part of quality assurance.
Typical QC testing for asphalt construction (overlays, patching, etc.) include aggregate quality (samples at the quarry or batch plant to examine fractured faces, sand equivalency, amount of fines, etc.), gradation of critical sieve sizes, nuclear density tests, material temperatures at the plant and at delivery/placement, degree of aggregate coating, and moisture content of aggregate. Part of the contractors QC system should also be to ensure that best practices are followed, such as proper surface preparation and minimizing broadcasting of loose mix across the max or ahead of the paver.
For concrete work, typical QC testing includes aggregate quality (again, samples at the quarry or batch plant), gradation, mix temperature, air content, water/cement ratio, and slump. The QC system should include measures that avoid unnecessary addition of water (and surely, not in excess of the maximum water/cement ratio) when the concrete truck arrives or while finishing.
Part of the contractor’s QC system/plan is to establish the frequency of these tests (often, minimum frequencies are specified to some degree by the contract specifications). In a future article, we will explore some of these in greater detail. Commonly (but dependent upon the agency’s policies), the owner’s inspector will observe these tests (and in some cases conduct the same tests concurrently) and record the results as part of the daily reports.
As part of the owner’s QA program, independent tests are often completed, some of which may be used to determine acceptance of the work and even 
the amount paid. For example, the owner may elect to obtain aggregate samples from the quarry or batch plant to test for gradation or moisture content; collect concrete test cylinders for compression testing; take asphalt cores of the finished mat for laboratory testing. Some owners establish as part of their specifications a range of final asphalt density (from core samples) where full payment is made, a range below that where partial payment is made, and a density below which the work is rejected (meaning no payment or the asphalt must be milled out and reconstructed properly).
A partial example of how QC requirements can be established by the owner can be found in the Delaware Department of Transportation’s (DelDOT) Standard Specifications for Road and Bridge Construction. From Section 106 – Material Quality and Testing Requirements, the contractor’s responsibility for quality control is established:
All Materials must be approved by the Department prior to use in the Work. Use of unapproved Materials is at the Contractor’s risk and unapproved 
Materials may be deemed unacceptable by the Engineer. The Engineer reserves the right to inspect and/or test all Materials at any time before or after incorporation into the Work. Removal and replacement of unacceptable Materials from the Work is solely at the Contractor’s expense. Tests performed by the Engineer are for quality assurance purposes only. The Contractor is responsible for quality control of the Materials as defined in Division 1000 of these Specifications and is responsible for the condition of the Materials until the Project is accepted.
From Division 1000 – Materials, a sweeping declaration of requirements is made:
Perform sampling, testing, and inspection of all Materials included in this Division in accordance with the guidelines set forth in the Department’s Materials and Research Manual, latest edition, unless otherwise specified in the Contract Documents.
Submit and track the proposed sources of all Materials to be incorporated in the Project. Material not included and approved on the “Source of Supply” is not permitted to be incorporated into the Work. All source approvals are contingent on the continued production of the respective Materials meeting the requirements of the Contract Documents.
Refer to Sections 106.01 Source of Supply and Quality Requirements and 106.02 Samples, Tests, and Referenced Sections for more detailed information.
You may sometimes feel that your project or your agency is too small to be concerned with quality control or quality assurance. If your pavements don’t show a pothole or extensive cracking ten years out, if your roads never pond water, if your sidewalks are without a pockmark for twenty years, if your curbs never crumble or crack, and if your stormwater inlets never settle, maybe you are right. But construction management relies on a “trust but verify” approach and the very process of requiring a contractor to talk or write about how quality of the constructed product will be assured puts your project on a positive footing where expectations are understood from the start. Some level of quality assurance (such as nuclear density testing or concrete test cylinders) on at least portions of your projects can reinforce the notion that you don’t intend to pay for a job that doesn’t meet contract specifications. For small agencies, a private testing firm can be employed on an occasional basis as part of the “verify” portion of the equation. Agency personnel can perform some tests on their own (temperature checks, concrete air and slump tests, etc.) with a small equipment expense and a little training.
Again, the takeaway here is less about terminology and more that, as local agencies, we can and should actively ensure that quality of the constructed product is what we bargained for and even with smaller projects, inspection, review of practices, and testing need to be a part of how we do that.
The Delaware T2/LTAP Center’s Municipal Engineering Circuit Rider is intended to provide technical assistance and training to local agencies and so if you have construction management questions or other transportation issues, contact Matt Carter at matheu@udel.edu or (302) 831-7236.
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