American Association of State Highway and Transportation Officials

Special Committee on Research and Innovation

FY2023 NCHRP PROBLEM STATEMENT TEMPLATE

Problem Number: 2023-D-24

Problem Title

Performance-Based Tests for Asphalt Emulsion Treatments as part of Agency Acceptance Programs

Background Information and Need For Research

AASHTO, the AASHTO Committee on Materials and Pavements (COMP), and the AASHTO TSP2 Emulsion Task Force (ETF) have worked together to develop agency-approved materials specifications and design practices for a wide range of asphalt emulsions and asphalt emulsion-based treatments. But tests (Laboratory and Field ) that could be used to determine the in-service performance and expected life cycle of these treatments applied according to these new AASHTO-approved material specifications and design practices are largely unavailable.

Many DOTs have ready access to Hot Mix Asphalt (HMA) tests and specifications that can be used to measure key characteristics that have been empirically shown to correlate with field performance. These agencies have also used these same tests and specifications to develop incentives/disincentives programs for the contractor. Examples of the types of HMA tests that have been used in DOT-based incentive/disincentive programs are lab molded density, in-place density, asphalt content, and gradation.

These same types of performance-based tests and specifications need to be determined for asphalt emulsion treatments to allow for these same types of incentive/disincentive programs to be developed by agencies for use with the emulsion contracting community.

The various asphalt emulsion treatments and their associated, approved AASHTO standards are listed below in Table 1.

Table1-Asphalt Emulsion Treatments and Approved AASHTO Standards

Literature Search Summary

Per Table 1, approved AASHTO specifications now exist for the individual materials, design, construction, and quality assurance (QA) relative to each of the specific asphalt emulsion treatments listed.

As an example for the chip seal emulsion treatment, see below:

M 140, Standard Specification for Emulsified Asphalt

AASHTO M 208, Standard Specification for Cationic Emulsified Asphalt

AASHTO M 316, Standard Specification for Polymer Modified Emulsified Asphalt

AASHTO MP 27, Standard Specification for Materials for Emulsified Asphalt Chip Seals

AASHTP PP 82, Standard Practice for Emulsified Asphalt Chip Seal Design

A similar grouping of specifications is also available for the micro surfacing, slurry seal, fog seal, scrub seal, sand seal, tack coat, cold recycling, and bonded surface treatments.

What is not readily available are the tests and specifications limits required to determine whether these treatments are manufactured correctly, constructed properly, and ultimately will perform as-expected in the field.

As a result, some DOTs have chosen to resort to short-term warranty programs to cover their chip seal (Idaho) and micro surfacing (Texas) projects. However, these are difficult to enforce without being able to rely on specific tests and specification limits that objectively measure properties that have been shown to correlate with the specific area(s) of interest relative to field-performance of the composite treatment.

Research Objective

This research would lead to the identification and/or development of various tests and specification limits related to the field performance of the selected asphalt emulsion-based treatments. In turn, this will allow DOT’s to develop performance-related acceptance criteria in conjunction with their quality assurance (QA) programs. Furthermore, incentive/ disincentive programs could also be developed for use with the emulsion contracting community that could lead to even longer in-service life for these treatments.

Urgency And Potential Benefits

Development of performance-based tests and specification limits for these asphalt emulsion-based treatments will enable DOTs to validate whether the design criteria are being met by the contractor. These can then also become the basis for incentives and disincentives programs included in contracts that will further help to insure better construction methods and quality of materials and workmanship. The project then has the best chance of being constructed as intended, so it will ultimately last longer. For example, it has been calculated that in Texas’ approximately $300 million annual chip seal program, adding only one additional year of life on only 20% of the lane-miles that are sealed can save over $9 million per year.

Implementation Considerations

Performance-based tests and specification limits must be identified and/or developed and then included in bid construction specifications. The performance-based tests need to have a direct effect on loss or gain relative to in-service life of the selected treatments to also allow for development of adequate incentive and disincentive programs.

Recommended Research Funding and Research Period

Time: 3 years

Funding: $400,000

Problem Statement Author(s): For each author, provide their name, affiliation, email address and phone.

Colin A Franco, RIDOT Associate Chief Engineer ; Co-Chair – AASHTO TSP2 Emulsion Task Force; Member – AASHTO RAC; TRB State Representative

Chris Lubbers, Kraton Polymers US, LLC; Technical Sales and Market Development Manager – Emulsions; Co-Chair – AASHTO TSP2 Emulsion Task Force

Darren Hazlett, University of Texas – Center for Transportation Research; Member – AASHTO TSP2 Emulsion Task Force

Potential Panel Members: For each panel member, provide their name, affiliation, email address and phone.

Members of the AASHTO TSP2 Emulsion Task Force

Members of the AASHTO Pavement Preservation Regional Partnerships (PPP’s)

Members of the AASHTO COMP TS 2a and TS 5b

Person Submitting The Problem Statement: Name, affiliation, email address and phone.

Colin A Franco, RIDOT Associate Chief Engineer ; Co-Chair – AASHTO TSP2 Emulsion Task Force; Member – AASHTO RAC; TRB State Representative.