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SWUTC Research Project Description

Seal Coat Quality: Does Low Cost Mean Low Quality?

University: Texas A&M University

Principal Investigator:
Cindy Estakhri
Texas Transportation Institute
(979) 845-9551

Funding Source: SPR Program

Total Project Cost: $103,431

Project Number: 0-6747

Date Started: 9/1/12

Estimated Completion Date: 8/31/13

Project Summary

Project Abstract:
Recently TxDOT administration has provided direction on the types of seal coat material that can be used on a particular facility based on traffic volumes. The more expensive modified binders are reserved for use on higher volume facilities while the very low volume facilities must be sealed with unmodified binders. Given the cost-cutting needs the department faces, this guidance is justified. However, it is just as important (economically) to get the maximum life out of a seal coat. For example, on a very low volume, rural road, a Grade 3 aggregate placed with a polymer modified asphalt (though a more expensive seal coat) may provide a surface that needs no maintenance for 12+ years.

The objective of this study is to evaluate the performance of seal coats and materials used statewide and develop guidelines based on cost and performance data regarding what materials should be used and where. To accomplish this goal, districts will be surveyed to understand their experience with the performance and cost of different types of seal coat materials and also to identify sections for further evaluation. Seal coats from the 2011 and 2012 season will be evaluated as well as seal coats from recent research projects. Test sections will be constructed in the four environmental regions to provide a direct performance comparison of different types of seal coat materials. And finally, seal coats will be fabricated in the laboratory and tested to determine the wear resistance of different types of aggregates and the adhesive capabilities of different binders.

Project Objectives:

The objective of this research study is to perform an extensive review statewide of seal coat performance and correlate to materials used (asphalt and aggregate), traffic volume and type, and environmental region.  Guidelines will be developed on optimizing selection of seal coat materials.

Task Descriptions:

TASK 1:  Meet with TxDOT Project Personnel

TASK 2:  Conduct Information Search

  • Subtask 2.1.  Literature Search and Review
  • Subtask 2.2.  Procurement of TxDOT Seal Coat Construction Plans
  • Subtask 2.3.  Procurement of Data from TxDOT Projects 0-1710 and 0-6616
  • Subtask 2.4.  TxDOT District Survey
  • Subtask 2.5.  Emulsion Task Force (ETF)

TASK 3:  Performance Evaluation of Seal Coats

  • Subtask 3.1.  Evaluation of Seal Coats From the Summer of 2011 and Summer of 2012 Season
  • Subtask 3.2  Evaluation of Test Sections from Recent Seal Coat Research Projects
  • Subtask 3.3.  Long-Term Performance Evaluations

TASK 4:  Plan and Construct End-to-End Test Sections

TASK 5:  Laboratory Evaluation of Seal Coat Performance

  • Subtask 5.1.  Measure Polish, Breakdown, and Wear Characteristics of Seal Coats
  • Subtask 5.2.  Measure Asphalt Binder Stiffness Development and Bonding Characteristics of Seal Coat Binders to Aggregates
  • Subtask 5.3.  Evaluate Binder Properties

TASK 6:  Document Findings and Recommendations

Implementation of Research Outcomes:
Research in progress.  Nothing to report at this time.

Impacts/Benefits of Implementation:

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