BACKGROUND

Geosynthetics are available in a wide range of forms and materials and are used in many applications. Geosynthetics are often used by highway agencies in conjunction with unbound base layers as a means for enhancing the performance of pavements. Test methods are currently available to estimate the performance enhancement resulting from the use of geosynthetics in the pavement structure (e.g., ASTM D8462, Cyclic Plate Load Tests to Evaluate the Structural Performance of Roadway Test Sections with Geosynthetics). However, there is concern about the validation of the test methods and reliability of the resulting estimates. Research is needed to evaluate the merits of the tests currently used for estimating the benefits of geosynthetics and, if necessary, enhance these test methods or develop new methods that can reliably estimate the contribution of geosynthetics to pavement performance. Such test methods will help highway agencies and others in making decisions regarding use of geosynthetics in pavement structure.

OBJECTIVE

The objective of this research is to develop a practical, validated laboratory test method for estimating the contribution of geosynthetics to pavement performance. The research shall be limited to asphalt pavements and use of geogrids and geotextiles in unbound base and subgrade.

Accomplishment of the project objective will require at least the following tasks.

TASKS

PHASE I

Task 1. Collect and review domestic and foreign literature, research findings, and information relevant to laboratory test methods for estimating the contribution of geosynthetics to pavement performance. This information may be obtained from published and unpublished sources and from public and private organizations.

Task 2. Based on the review performed in Task 1, identify and evaluate the merits and deficiencies of available test methods and recommend potential tests, modifications thereof, or new methods for consideration in Phase II to develop a reliable laboratory test method for estimating the contribution of geosynthetics to pavement performance.

Task 3. Based on the work performed in Task 2, prepare a detailed work plan to be executed in Phases II and III to (1) develop a validated test method for estimating the contributions of geosynthetics to pavement performance and (2) prepare supplementary material to support adoption and implementation. Accelerated pavement testing may be considered for validation. The plan shall provide specific information on the different aspects of the proposed work (e.g., the approach for addressing the deficiencies of the recommended test methods and the process for validating the recommended method).

Task 4. Prepare and submit Interim Report 1 that documents the research performed in Tasks 1 through 3. Following review of the interim report by the NCHRP, the research team will be required to make a presentation to the NCHRP project panel. Work on Phase II of the project will not begin until Interim Report 1 is approved and the Phase II work plan is authorized by the NCHRP. The decision on proceeding with Phase II will be based on the contractor’s documented justification of the updated work plan.

PHASE II

Task 5.  Execute the Phase II work plan approved in Task 4. Based on the results of this work, develop the test method.

Task 6. Prepare draft language for consideration by American Association of Highway and Transportation Officials (AASHTO) to incorporate the research results into a future edition of the AASHTO Standard Specifications for Transportation Materials and Methods of Sampling and Testing, and AASHTO Provisional Standards.

Task 7. Prepare and submit Interim Report 2 that documents the recommended test method and the draft language. Following review of the interim report, the research team will be required to make a presentation to the NCHRP project panel. Work on Phase III of the project will not begin until the report is reviewed and the Phase III work is authorized by the NCHRP.

PHASE III

Task 8. Review and consider the comments on Interim Report 2 and revise the recommended test method and draft language and prepare a draft report documenting the research performed in the project.

Task 9. Prepare presentation material, in a PowerPoint or other format, for use in webinars and presentations to facilitate the use and adoption of the proposed test method.

Task 10: Prepare a stand-alone technical memorandum titled “Implementation of Research Findings and Products” to facilitate implementation of the proposed test method.

Task 11. Submit (1) a draft final deliverable that includes (a) a research report documenting the work performed in the project and used to develop the proposed test method, (b) the proposed test method, (c) the draft language, (d) the presentation material, and (e) the implementation plan, and (2) a final deliverable that addresses the review comments.

STATUS: Contract pending.