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Using Polymer Modified Asphalt Emulsions in Surface Treatments A ...

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(80, 97), whereas French experts recommended the Vialit Pendulum Test (98).<br />

The best tool to date appears to be the MMLS3 procedures as developed by Dr.<br />

Richard Kim’s group at N.C. State for the North Carol<strong>in</strong>a DOT (99, 100).<br />

Although too expensive to advance for specification purposes, it rema<strong>in</strong>s an<br />

excellent research tool aga<strong>in</strong>st which the predictive capabilities of less expensive<br />

performance tests can be compared. This subject rema<strong>in</strong>s a significant data gap,<br />

with no specific project recommendations at this time.<br />

• Microsurfac<strong>in</strong>g vs. <strong>Polymer</strong> <strong>Modified</strong> Slurry: Microsurfac<strong>in</strong>g is formulated to<br />

provide significantly higher performance than Slurry Seals either with or without<br />

polymer. From a use perspective, Microsurfac<strong>in</strong>g should be used for rut-fill<br />

applications and for high-traffic pavements with ADT exceed<strong>in</strong>g 1000.<br />

Microsurfac<strong>in</strong>g also conta<strong>in</strong>s emulsifier packages that break quickly, so that<br />

traffic can usually be returned <strong>in</strong> one hour or less. Where traffic control is a<br />

problem due to urban traffic, narrow roads or long detours, the faster cur<strong>in</strong>g<br />

microsurfac<strong>in</strong>g might even be specified for lower volume roads.<br />

• Microsurfac<strong>in</strong>g Performance Tests: The ISSA document A143<br />

“Recommended Performance Guidel<strong>in</strong>es for Micro-Surfac<strong>in</strong>g” was cited by<br />

survey respondents as the best available current practice for performancerelated<br />

test procedures (39). Performance tests <strong>in</strong>clude Wet cohesion, Excess<br />

<strong>Asphalt</strong> by LWT Sand Adhesion, Wet Stripp<strong>in</strong>g, and Wet Track Abrasion Loss<br />

after one day soak and after six day soak. These tests should be used as pay<br />

items.<br />

o<br />

Newly proposed tests for mix design and performance: At a recent<br />

ETG meet<strong>in</strong>g, Jim Moulthrop of Fugro, Inc. provided an update of a soonto-be-completed<br />

research study updat<strong>in</strong>g mix design methods for<br />

Microsurfac<strong>in</strong>g (101). Significant contributions from this study <strong>in</strong>clude an<br />

automated test for cohesion, a German method to predict mix<strong>in</strong>g time by<br />

measur<strong>in</strong>g mixer torque, and a French adaptation of the wet track<br />

abrasion test us<strong>in</strong>g wheels <strong>in</strong> place of the rubber tube. It is recommended<br />

99

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