The National Academies

NCHRP 14-44 [Active]

Guide Specifications for the Construction of Slurry Seals, Scrub Seals, and Tack Coats

  Project Data
Funds: $175,000
Staff Responsibility: Amir N. Hanna
Research Agency: University of Arkansas
Principal Investigator: Andrew Braham
Effective Date: 9/2/2020
Completion Date: 3/1/2022

BACKGROUND: Pavement preservation provides a means for maintaining and improving the functional condition of an existing highway system. Although pavement preservation is not expected to substantially increase structural capacity, it generally leads to improved pavement performance and longer service life. Slurry seals and scrub seals are frequently used as pavement preservation treatments for flexible pavements. Slurry seals are used to mitigate oxidization and scrub seals are used to seal cracks and prevent moisture intrusion. Tack coats are applied to promote bonding of the preservation treatment to the pavement. Although a great deal of information on the design, materials, and construction practices of these treatments is available, there is no nationally accepted guidance on their construction. There is a need to develop guide construction specifications to help state departments of transportation (state DOTs) apply these treatments more effectively and achieve the most benefit of their application.

OBJECTIVE: The objective of this research is to develop recommended guide specifications for the construction of slurry seals, scrub seals, and tack coats as used in preservation treatments.

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


PHASE I: (1) Collect and review relevant domestic and foreign literature, research findings, and information relative to the construction of slurry seals, scrub seals, and tack coats as used in preservation treatments. This information may be obtained from published and unpublished reports, survey of state and local transportation agencies, and contacts with transportation agencies, industry, and other public and private organizations. Identify material of relevance to development of the guide specifications for further consideration in this research. (2) Prepare an updated, detailed work plan for Phase II that includes a process for developing separate guide specifications for (1) slurry seals, (2) scrub seals, and (3) tack coats.  It is expected that the specifications will address practices applicable to different parts of the United States and the variety of materials used; methods of construction and quality assurance; methods of measurement, warranty, and payment; and other relevant items with consideration to performance. (3) Prepare an interim report that documents the research performed in Tasks 1 and 2. Following review of the interim report by the NCHRP, the research team will be required to make a presentation to the project panel. Work on Phase II of the project will not begin until the interim report 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: (4) Execute the plan approved in Task 3. Based on the results of this work, prepare the recommended guide specifications for slurry seals, scrub seals, and tack coats as stand-alone documents suitable for consideration and adoption by the American Association of State Highway and Transportation Officials (AASHTO). Relevant commentary should be included. (5) Prepare a presentation in a Power Point or other format to facilitate adoption by AASHTO. Also, present the features of the guide specifications and anticipated user benefits to the AASHTO Committee on Materials and Pavements, (6) Prepare a final deliverable that documents the entire research effort.  The recommended guide specifications shall be prepared as stand-alone documents.


 Status: Research in progress. 


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