6.3 Quality Assurance (QA) and Quality Control (QC)

In construction quality management, the terms Quality Assurance (QA) and Quality Control (QC) are frequently conflated, yet they represent two fundamentally different, albeit highly interdependent, aspects of a project's quality system. The Construction Manager must understand the precise boundaries of these two functions, as the allocation of QA and QC responsibilities directly impacts contract administration, risk mitigation, and project success.

Quality Assurance (QA) vs. Quality Control (QC): Comparative Analysis

The core distinction between the two lies in their orientation and execution:

• Quality Assurance (QA) is process-oriented and proactive. It comprises all the planned, systematic processes and activities established before work begins to provide confidence that the project will meet the specified standards. QA is designed to prevent defects from occurring in the first place by designing, auditing, and optimizing the processes used to produce the deliverables. It answers the question: "Are we using the correct systems and procedures in the correct way to ensure success?"
• Quality Control (QC) is product-oriented and reactive. It consists of the specific operational techniques, inspections, and physical tests executed during and after construction to verify that the physical work conforms to the plans and specifications. QC is designed to detect and correct defects in the actual product before it is finalized or covered up. It answers the question: "Did we build this specific element in conformance with the contract documents?"

The following table contrasts the two functions:

Contractual Quality Responsibilities under CMAA Standards

Under the Construction Management Association of America (CMAA) Standards of Practice, the allocation of QA and QC responsibilities depends heavily on the project delivery method chosen by the owner:

1. Agency Construction Management (ACM)

In an ACM delivery method, the CM acts as the owner's advisor and agent, while having no direct contractual relationship with the general contractor or trade contractors.

• Contractor's Role: The general contractor holds sole responsibility for Quality Control. Because the contractor controls the daily means, methods, labor, and materials, they must perform all physical inspections and testing.
• CM's Role: The Agency CM is responsible for Quality Assurance. The CM does not perform day-to-day inspections to tell the contractor how to do their work. Instead, the CM reviews the contractor's QC plan, audits their inspection logs, verifies that independent testing agencies are properly certified, and conducts periodic, independent quality audits (spot-checks) to verify that the contractor's QC system is working.

2. Construction Management at Risk (CMAR)

In a CMAR delivery method, the CM acts as the general contractor during the construction phase, holding the direct subcontracts and guaranteeing the project cost (GMP) and schedule.

• CM's Role: The CMAR has a dual responsibility. Vis-a-vis their subcontractors, the CMAR must establish and enforce a comprehensive Quality Control (QC) program to inspect the sub's work. Vis-a-vis the owner, the CMAR must demonstrate conformance through their quality system.
• Owner/Consultant's Role: The Owner, often assisted by the Architect/Engineer or an independent owner's representative, performs the Quality Assurance (QA) function to audit the CMAR's QC compliance.

The USACE Contractor Quality Control (CQC) Model

The modern construction quality paradigm was heavily influenced by the U.S. Army Corps of Engineers (USACE) and the Naval Facilities Engineering Command (NAVFAC). Their model establishes a strict separation between Contractor Quality Control (CQC) and Government Quality Assurance (QA):

Under this model, the contractor is required by contract to establish a CQC system managed by a dedicated CQC System Manager. The CQC Manager is an independent staff member on site who has the authority to stop non-conforming work immediately. To prevent conflicts of interest, the CQC Manager reports directly to a corporate executive of the contractor's firm, completely bypassing the on-site Project Manager and Superintendent, who are naturally driven by schedule and cost pressures. The government's role is strictly QA—auditing the CQC Manager's records and conducting validation testing.

Components of a Construction Quality Management Plan (CQMP)

A project-specific CQMP is the foundational document that integrates both QA and QC into a single operational roadmap. A comprehensive CQMP must contain the following sections:

1. Quality Policy and Objectives: A clear statement from executive leadership outlining the project's quality metrics and goals.
2. Organizational Structure and Authority: A project chart detailing roles, responsibilities, and reporting lines. It must explicitly establish the independence of the QC staff.
3. Document Control Protocol: Procedures for managing, distributing, and updating contract drawings, specifications, RFIs, submittals, and Change Orders to prevent crews from working off outdated documents.
4. Procurement and Material Control: Methods for pre-qualifying suppliers, reviewing product certifications, and inspecting materials upon delivery to ensure they match approved submittals.
5. Inspection and Testing Plan (ITP): A matrix detailing every test required by the specifications, the reference standard (e.g., ASTM, ACI, AWS), the required frequency, the responsible party (QC or QA), and the witness points.
6. Non-Conformance Management: A formal workflow for identifying, documenting, correcting, and closing out deviations from the contract requirements.
7. Auditing and Continuous Improvement: A schedule for regular internal and external audits to evaluate QMS compliance and update procedures as necessary.

Realistic Construction Scenario: Concrete Foundation Wall Placement

To illustrate the practical interplay of QA and QC in the field, consider the construction of a reinforced concrete foundation wall:

Quality Control (QC) Activities (Executed by Contractor)

• Pre-placement: The contractor's QC inspector verifies that the concrete formwork dimensions are correct, form release agent has been applied, rebar size and spacing match the shop drawings, and clearance (concrete cover) is maintained.
• During placement: The QC inspector checks the concrete batch tickets at the delivery truck to ensure the mix matches the approved submittal, the water-cement ratio is not exceeded, and the time limit since batching (usually 90 minutes) has not expired. The inspector measures concrete slump, temperature, and air content, and casts concrete test cylinders (typically 5 cylinders per 100 cubic yards).
• Post-placement: The crew vibrates the concrete to prevent honeycombing and implements the specified curing method (e.g., wet curing blankets for 7 days).

Quality Assurance (QA) Activities (Executed by CM)

• Oversight: The CM audits the contractor's pre-placement checklists. They inspect the concrete batch plant's certifications and verify that the laboratory testing the concrete cylinders is accredited (e.g., AASHTO or ASTM standards).
• Verification: The CM's inspector performs spot inspections of the rebar clearances and witnesses the contractor's QC inspector casting the cylinders to ensure they are stored in a temperature-controlled initial curing box as required by ASTM C31.

Resolution of a Quality Failure (Failed Compression Test)

Suppose the 28-day compression test reports that the concrete strength is only 3,200 psi, while the specifications require a minimum of 4,000 psi. The CM initiates the following QA/QC resolution process:

1. Issue Non-Conformance Report (NCR): The CM issues an NCR to the contractor, halting any structural loading on the wall.
2. Audit the Testing Process (QA Investigation): The CM audits the testing lab's records and concrete batch tickets to rule out sampling or curing errors.
3. Non-Destructive Testing (QC Action): The contractor conducts non-destructive testing (NDT), such as a Schmidt Rebound Hammer test or Windsor Probe test, to estimate the in-place concrete strength.
4. Core Drilling (Destructive Verification): If NDT is inconclusive, the contractor drills core samples from the actual wall (per ASTM C42) and tests them in compression. This represents a destructive test to verify the actual strength of the wall.
5. Engineering Evaluation: The Engineer of Record (EOR) reviews the core test results. If the cores show the concrete is structurally adequate, the EOR may recommend accepting it "Use-As-Is," typically in exchange for a credit to the owner and an extended warranty. If it is structurally inadequate, the contractor must demolish and rebuild the wall (Rework).
6. NCR Closeout: Once the remediation is approved and executed, the CM verifies the paperwork and officially signs off, closing the NCR.