BACKGROUND
Chip seal aggregate embedment has a significant influence on chip seal performance. Too little embedment can cause raveling and too much embedment can lead to bleeding. In both situations, safety and performance are compromised. Proper aggregate embedment shall be evaluated as a critical factor when considering a chip seal treatment's design, construction, and performance.
Research is needed to develop a field test method(s) to measure chip seal aggregate embedment rapidly and accurately.
OBJECTIVE
The objective of this research is to identify, adapt, or develop a rapid field test method(s) to determine the percentage embedment depth of a uniformly placed chip seal of known aggregate gradation.
The term “rapid” for this project refers to a test method(s) that can be used as part of the quality control (QC) process, and can provide its results after the initial chip seal sweeping, allowing for real-time adjustments during the construction process.
RESEARCH PLAN
At a minimum, the anticipated tasks include:
· Conduct a critical literature review of relevant research, methodologies, tools, and technologies (henceforth “tests”) that have been used or could be used in determining the actual percent embedment of chip seal aggregate. Conduct a preliminary evaluation of the tests listing pros and cons and recommend tests that could potentially meet the project objective. Submit Interim Report No. 1 with a synthesis of the critical literature review and the preliminary evaluation.
· Based on Interim Report No. 1 and the proposer’s experience and knowledge, develop a detailed work plan to further evaluate the recommended tests to meet the project objective. Submit Interim Report No.2 with the detailed work plan, including proposed evaluation criteria and rationale supporting the work plan. The proposer shall give a high priority to the simplicity and practicality of the tests. The proposer will need NCHRP approval of Interim Report No. 2 before proceeding with the project.
· Execute the approved work plan and determine tests that best accomplish the research objective. Develop documents with draft language for the test procedure(s) and supporting construction recommendations. Consider that the rapid field tests could be used to address contractor workmanship issues for real-time adjustments and also can complement performance assessment relative to the chip seal embedment. Submit Interim Report No. 3. Interim Report No. 3 must document the research work thus far and present a detailed outline of the final deliverables.
Anticipated final deliverables will include:
1. A conduct of research report documenting the project activities.
2. Based on the research results, prepare draft language describing in detail the selected test procedure for review and consideration by the AASHTO Committee on Materials and Pavements (COMP). The draft language must include a recommended methodology to determine the aggregate’s least common dimension to reference the percent embedment depth.
3. Based on the research results, prepare draft language with the supporting construction recommendations to determine the embedment depth of chip seal aggregate for review and consideration by the AASHTO COMP.
4. Develop a framework based on field aggregate embedment as measured by the selected tests for developing an incentive and disincentive program to maximize the performance of chip seals.
5. A technical memorandum titled “Implementation of Research Findings and Products”. Additionally, include a roadmap for collecting data to support the incentive/disincentive framework and provide guidance on how project-level conditions and percent aggregate embedment relate to the expected performance of chip seals.
STATUS: Research in progress.
