Long-life pavement systems (pavement layer, subbase layer, and subgrade foundation) have not been achieved by most SHAs due to:

1)      failure to design the pavement and foundation materials as an interrelated system whereby the foundation materials are designed to meet the pavement design requirements,

2)      lack of a modern pavement foundation design methodology that enables the foundation layers to be engineered for optimal performance considering material selection, layer thicknesses, pavement design requirements, construction practices, cost, and durability of as-constructed layers,

3)      lack of meaningful quality assurance (QA) sampling and measurement for field verification of as-constructed pavement foundation support leading to paving over deficient and/or un optimized foundations,

4)      inadequate understanding of how pavement and foundation materials can be optimized and constructed without compromising long-term performance,

5)      lack of established engineering relationships between current indirectly measured acceptance criteria and performance, thus creating a barrier to continuous specification price adjustment provisions that are needed to incentivize quality material selection and construction.

Although advancements in pavement layer design tools and software have emerged over the last few decades, practices for the design, construction quality control, and quality assurance verification of the pavement foundation materials (subbase, subgrade, embankment) have not advanced resulting in most pavement foundations being specified, not engineered, and not verified prior to paving. Further, the current practice of using (legacy) specified pavement foundation materials/thicknesses often results in reliance on thick pavements with relatively thin, variable, unoptimized foundation layers subject to deformation over time. Advancement in pavement foundation design and construction practices is critical to achieving long-life pavement systems. 

Main study objectives include:

1)      Provide technical support to SHAs for building long-life pavement systems pilot projects using optimized pavement and foundation design solutions that achieve the design assumptions for the foundation materials, including developing a Quality Assurance Program (QA) that addressed field performance verification measurements during construction. Technical support elements include:

a.       Determine, on statewide basis (representative materials), if the design values are being achieved using spot plate load tests. The test results will be used to populate a database for each SHA with results of what is being achieved for various foundation materials with current specifications compared to design assumptions. This data is strategic in understanding where there is opportunity to significantly improve pavement performance and optimize designs.

b.       Determine, at project level, if the construction quality verification is delivering design modulus and verify with 100% mapping.

c.       Establish a process for QA in compliance with 23 CFR Part 637, Subpart B (Quality Assurance Procedures for Construction) and provide technical assistance to SHA.

d.       Develop draft specifications that incentivize quality the foundation layers.

2)      Develop the methodology for a modern pavement foundation design.

Proposed project activities include:

• Demonstration projects.
• Develop a process for QA of pavement foundations using intelligent construction technologies that is compliant with 23 CFR Part 637, Subpart B.
• Develop a library of pavement foundation modulus values for state specific materials.
• Introduce SHA to direct measurement of material stiffness using plate load testing and roller mapping.
• Develop a process for improving the long-term performance of foundation materials through improved compaction, optimization of the gradation of unbound materials, mechanical reinforcement material and chemical stabilization.
• Develop guidelines/design procedures for engineering long life pavement foundations including layer thickness, material selection, and cost.
• Demonstrate advantages of building long life pavement foundations.
• Develop designs for pavement foundations that will function under flooding conditions.
• Develop a process for annual performance monitoring by each SHA and sharing the database with all participants.

Funding:

1. Desired total commitment from each partner is $150,000 split between 2026-2030, generally achieved through five years at $30,000 per year.
2. SPR Part B Waiver will be requested.

Technical Representative Duties:

1. Commit to building a demonstration project with minimum size of 1 mile.
2. Commit to providing coordination and access to selected projects for plate load testing on representative pavement foundations.
3. Support a performance monitoring program of projects built by annually monitoring performance of pilot projects for ride and distresses.
4. Participate in the technical advisory group overseeing the development of the design methodology requirements for engineering pavement foundations.

New Members:

1. This pooled fund is always accepting new members. Please inquire with the Lead Study Contact noted above to join this effort.