Jeong Hyuk Im

Methods for Fog Seal Field Test with Polymer-Modified Emulsions: Development and Performance Evaluation

Findings from a laboratory evaluation of fog seal emulsions are presented. Curing time and adhesive behavior of polymer-modified emulsions (PMEs) were compared with those of unmodified emulsions as fog seal materials. The study showed that polymer modification could improve certain properties of emulsions, such as an increase in adhesion. The evaporation test and the pneumatic adhesion tension testing instrument were used to investigate emulsion curing and adhesive behavior. Also, the rolling ball test and the damping test were developed as in situ test methods to determine an appropriate traffic opening time for roadways treated with fog seals. Finally, the third-scale Model Mobile Load Simulator was employed to compare the performance properties of the fog seal emulsions. The following main findings are presented: use of PMEs improved the emulsion bond strength and lessened the time a road was closed to traffic; PMEs showed more effective emulsion curing rates than did unmodified emulsions; strong relationships existed between the bond strength and both the measured rolling distance (from the rolling ball test) and the measured percentage of stained area (from the damping test); field test methods could be used to help determine whether emulsions were fully cured; and PMEs exhibited better aggregate retention and bleeding performance properties than did unmodified emulsions as a fog seal.

Tack Lifter for In Situ Measurement of Effective Emulsion Application Rates

Emulsion application rates are critically important to the performance of pavement surface treatments and tack coats. In this study, the tack lifter was introduced as a means to measure in situ effective emulsion application rates at specific locations along the length of paving. The tack lifter is a simple, weighted device that is placed on top of a superabsorbent foam sheet applied to a paving surface. The absorbent sheet soaks up emulsion from the roadway surface to get a spot check of the amount of emulsion on the surface. The device measures the effective emulsion application rate on the paving surface, neglecting emulsions absorbed into the paving surface. Laboratory studies of emulsion application onto chip seal and hot-mix asphalt concrete surfaces demonstrate the ability of the tack lifter to capture the sensitivity of emulsion absorption to pavement surface texture. In addition, preliminary tack lifter field trial results are presented to demonstrate its use as a quality control field test.

Addressing Raveling Resistance in Chip Seal Specifications

Chip seals are applied to existing roadways to slow deterioration and improve pavement surface conditions without increasing the pavement’s structural capacity. The raveling of chip seals can cause damage to vehicles and thus is a safety concern. Raveling resistance is related to both material application rates and material properties. The current chip seal specifications fail to adequately address the material-related aspects of raveling resistance. This study seeks to develop recommendations to address raveling resistance in future chip seal specifications. Strain sweep binder tests, binder bond strength (BBS) tests, and Vialit chip seal mixture tests were conducted to assess early raveling, late raveling, and wet raveling at two intermediate temperatures. The results demonstrate that the bond that develops between the residual binder and the aggregate is highly dependent on the interaction between the emulsion and the aggregate during curing. The importance of emulsion–aggregate compatibility in raveling resistance indicates that raveling resistance cannot be addressed in binder specifications alone. Rather, it is recommended that intermediate temperature raveling resistance should be addressed during chip seal mixture design. Vialit and BBS tests, in which emulsion is cured on rock, can both be used to effectively quantify the aggregate loss potential of a chip seal. These two tests are able to capture the benefits of polymer modification and produce results that correlate. However, the Vialit tests are easier to implement than the BBS tests and require no expensive equipment. Therefore, Vialit tests are recommended to address early, late, and wet raveling resistance in future chip seal specifications.

Performance Evaluation of Chip Seals for Higher Volume Roads Using Polymer-modified Emulsions: Laboratory and Field Study in North Carolina

This paper presented a study to evaluate the performance of chip seals for higher traffic volume roads. The evaporation test, bitumen bond strength (BBS) test, and Vialit test were used to investigate curing and adhesive behavior. For the laboratory performance, the third-scale model mobile load simulator (MMLS3) was employed to test for aggregate retention, bleeding, and rutting performance. In field, a total of ten test sections were constructed on three different traffic volume roads using different materials and seal types. Some of the field samples were extracted and moved to the laboratory for performance testing. Also, the field sections were monitored to compare the field performance with the laboratory performance. The main findings presented in this paper were as follows: (1) the laboratory test results indicated that the use of polymer modified emulsions (PMEs) improved the chip seal performance in all areas, i.e., curing and adhesive behavior, aggregate retention, bleeding, and rutting; and (2) the field observations indicated that PME-A (styrene butadiene styrene (SBS) polymer-modified emulsion) performs the best of all the emulsions, regardless of seal type and traffic volume.