Performance Measures of Warm Asphalt Mixtures for Safe and Reliable Freight Transportation Phase II: Evaluation of Friction and Raveling Characteristics of Warm Mix Asphalt Mixtures with Anti-stripping Agents

Authors

Hosin David Lee Ph.D., P.E., University of Iowa
Yongjoo Thomas Kim Ph.D.

Date of this Version

2011

Document Type

Article

Citation

Report # MATC-UI: 373 Final Report 25 -1121-0001-373

Comments

2011 Copyright of Mid-America Transportation Center

Abstract

The viscosity of asphalt decreased significantly when 0.5% of WMA additive was added,but it remained relatively steady as the dosage rate increased up to 3.0%. The reduction pattern in viscosity as the dosage rate increases was similar for both CECABASE RT® and LEADCAP at all test temperatures of 120°C,125°C, 130°C and 135 °C and a similar pattern was observed for both Sasobit® and Rediset. Based on the ABCD test device, the virgin asphalt binder PG 64-34 cracked at -51.0°C and the PG 64-28 cracked at -41.3°C. As the WMA additives were increased from 0.5%to 3.0%, the cracking temperatures increased slightly,but remained steady near the cracking temperature of the virgin asphalt binder. The ABCD test results confirmed that the cracking temperature of asphalt binder was not significantly affected by any of these four WMA additives. The BPN value steadily decreased as the specimen surface was abraded by a rotating rubber although the MTD value did not change significantly. The most significant change in BPN has occurred between 30 and 45 minutes of abrasion whereas no significant change was observed between 45 and 65 minutes of abrasion. The control WMA without additive exhibited the lowest Tensile Strength Ratio (TSR) value of 53.3%, which increased to 66.6% with lime and 83.5% with an Anti-stripping agent (ASA). WMA-Sasobit exhibited 73.7% but it slightly decreased to 72.7% with lime and 72.3% with ASA. WMA-LEADCAP exhibited 80.3% but it decreased to 78.5% with lime and increased to 81.4% with ASA. The control HMA exhibited 82.7% and it increased to 89.3% with lime and 92.6% with ASA. It can be concluded that TSR values of both WMA-Sasobit and WMA-LEADCAP were not affected by lime or ASA. A more extensive study should be performed quantifying the temperature-viscosity relationship of asphalt mixed with varying amounts of WMA additives at different temperatures. An additional study should be performed on the effect of lime and anti-stripping agent on WMA mixtures with various additives. It is recommended that the skid test should be performed on WMA pavements in the field after several years of service.