2016 RAC Annual Meeting Sweet Sixteen In-situ Determination of Emulsion Application Rates for Tack Coats and Surface Treatments (RP2014-03) Neil Mastin, PE

Introduction Researchers Research Agency Cassie Castorena (PI) Mary Rawls Jeong Hyuk Im Research Agency North Carolina State University Contact Info / Additional Info PI cahintz@ncsu.edu https://www.ccee.ncsu.edu/people/cahintz/ TRB Paper https://trid.trb.org/view.aspx?id=1392765 Project Page: https://connect.ncdot.gov/projects/planning/ pages/ProjDetails.aspx?ProjectID=2014-03

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

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

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 0.05 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.

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

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

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

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.

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