About materials testing in Minnesota
The FWHA Code of Federal Regulations [Code 23 CFR Ch. I (4–1–11 Edition) Title 23. Part 637] mandates the MnDOT Technical Certification Program. For Minnesota and MnDOT to receive federal funding for highway and bridge projects, we must have a Quality Control, Quality Assurance, and Independent Assurance Program in place to ensure qualified and certified technicians test and inspect materials used on those projects. Minnesota also has chosen to extend this requirement to all state and some local government aid highway projects.
The types of materials that are tested are aggregate (rocks), concrete, bituminous (asphalt), soil, and various other materials used in roadway and bridge construction.
MnDOT has four specialty units, each responsible for materials used on roadways and bridges:
- Bituminous (asphalt)
- Grading and Base (soil, sand, and rocks)
MnDOT staff at these units work collaboratively with each other, the Technical Certification program staff, industry representatives, and people working in the field.
Sampling and testing
There are three key levels to the materials sampling and testing process, done by people with Tester certifications (formerly known as Level 1 certifications).
Quality Control (QC) is done by qualified and certified Testers who work for the contractor (the company that is building the road or bridge) or a producer (the company that supplies the materials). At designated times throughout the project, the Testers sample, test, and record and report on the roadway and bridge materials to make sure the contractor/producer is meeting the specifications described in the contract.
Quality Assurance (QA) is done by qualified and certified Testers who work for the “owner” of the roadway or bridge project (MnDOT or other designated agencies). QA Testers test the same materials as the QC Testers, using what is known as “companion samples” that are split and shared by QC and QA testers. This QA testing is also done at designated times, but less often than the QC testing.
The goal is for the owner to verify that the contractor/producer test results are accurate and confirm that the materials meet the specifications in the contract. These Testers are typically MnDOT staff, consultants hired by MnDOT, or county/city personnel.
Independent Assurance Program
The Independent Assurance Program (IA) provides a layer of oversight to the testing process on federally funded projects. The IA staff members do an independent, unbiased evaluation of all the sampling procedures, testing procedures, and testing equipment used to determine the quality of the products specified in every roadway or bridge project contract.
Each MnDOT District has at least one IA staff member responsible to review and report on all Federal Aid projects in their district. As part of this work, they check the testing equipment, including the calibrations, and conduct annual reviews of all project Testers, both those doing Quality Control (for contractors and producers) and Quality Assurance (for MnDOT and other agencies).
In the system, there also is another important layer of oversight that is done by Inspectors. The Inspector holds an advanced certification (formerly known as Level 2), serves in a decision-making role providing project supervision or oversight (e.g., Chief Inspector, Mix Designer, etc.), and is employed by MnDOT or other designated agencies.
The role of the Inspector is to represent the Project Engineer and oversee, inspect, and evaluate the production and placement of the roadway and bridge materials, as described in MnDOT plans, specifications, and contracts. It is the Inspector who gives final approval to the placements of materials, when the specifications have been met, and then authorizes payment from the owner to the contractor.