1. 2016 RAC Annual Meeting Sweet Sixteen
In-situ Determination of Emulsion Application Rates for Tack Coats and Surface Treatments (RP )
Neil Mastin, PE

2. Introduction Researchers Research Agency
Cassie Castorena (PI)
Mary Rawls
Jeong Hyuk Im
Research Agency
North Carolina State University
Contact Info / Additional Info PI
TRB Paper
Project Page: pages/ProjDetails.aspx?ProjectID=

3. Problem Statement
The Emulsion Application Rate (EAR) is critical to performance of tack coats and surface treatments
Very few test methods exist for Quality Control (QC) of EARs: Only national standard: ASTM D 2995
Existing test methods target calibration rather than in- situ measurements of EAR along length of paving
ASTM D 2995 Test Method A
ASTM D 2995Test Method B

4. Research Performed
Overview of Tack Lifter Test
Developed Tack Lifter for in-situ determination of EARs
Provides measurement of
“Effective” EAR (i.e., non- absorbed) when applied to pavement
Applied EAR when applied to plate
Tack Lifter rigorously evaluated using field and laboratory experiments to assess
Effect of surface texture on pavement emulsion absorption
Longitudinal variability in applied EARs
Transverse variability in applied EARs
Sheet and frame placed on pavement or plate
Weighted device applied to sheet
Sorbent sheet with emulsion weighed to determine EAR

5. Research Results
The Tack Lifter is a simple and efficient means for in-situ measurements of applied EARs and “effective” EARs
The amount of emulsion absorbed by a paving surface is influenced by surface type and texture.
Emulsion absorption by pavements can be significant (on the order of gal/yd2). The target applied EAR should be adjusted to account for emulsion lost to absorption.
Trends in transverse EAR variability consistent longitudinally, indicating transverse EAR variability should be assessed prior to construction
Applied EARs can vary over relatively short segments of road. Investigations suggest changes in curvature and / or grade impact variability in applied EARs.

6. Research Recommendations
Proposed framework for QC of EARs
QC Measure
Test Method
When?
Where?
Transverse Variability in Applied EAR
ASTM D2995 Test Method B
Prior to construction
-----
Pavement Absorption
Tack Lifter applied to late and surface
Wheel Paths
Longitudinal Variability in Applied EAR
Tack Lifter applied to elevated plate
Every 0.5 miles along length of paving
Lane Center
Could add final report link if it has been published

7. Implementation Status
Draft AASHTO standard for Tack Lifter test has been developed
Instrotek, Inc. will produce Tack Lifter devices for purchase

8. Implementation Strategy
The Tack Lifter can be used to:
Determine adjustments to the target EAR to account for emulsion lost to absorption into the pavement prior to construction
Assess longitudinal variability in EARs during construction
A Technology Transfer project is under consideration by NCDOT R&D

9. Value of Implementing the Research
The research product will result in improved QC of EAR.
Improved QC of EARs will:
Lead to prolonged pavement service life
Decreased life cycle costs
Enhanced safety.

10. Return on Investment
Until this product has been in service and results can be compared, direct ROI is difficult to compute
Resurfacing costs in North Carolina are typically $50,000 to $200,000 per paved lane- mile and chip seal costs are typically $10,000 to $50,000 per lane-mile
The potential increased life and reduced maintenance would result in a tremendous long-term payback