Evaluation of the Moisture Susceptibility of WMA Technologies (2014) / Chapter Skim
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4History and Definition HMA is a well-established paving material with proven performance used on 94 percent of the more than 2.5 million mi (4.0 million km) of paved roads in the United States (FHWA 2008, NAPA 2010)
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5 Project Objectives and Scope NCHRP has committed funding for the following six research projects to address the major remaining issues associated with WMA: • Mix design (NCHRP Project 9-43 -- Mix Design Practices for WMA)
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6between laboratory tests and field performance, and (3) evaluation of the differences in volumetric and mechanical properties measured on different specimen types.
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7 Authors Year Conditioning Protocols Laboratory Tests Conclusions Al-Qadi et al. 2010 Reheat to Tc for offsite PMLC E*
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8moisture susceptibility as compared to HMA, with mixed conclusions with regard to rutting of WMA as compared to HMA. WMA Performance Evolution Results from the laboratory conditioning experiment indicated that the initial stiffness of WMA is less than the stiffness of conventional HMA but that this gap may be reduced over time in the field.
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9 (continued on next page) Authors Year WMA Technologies Topic Laboratory Tests Conclusions Hearon and Diefenderfer 2008 Sasobit Moisture Susceptibility IDT Strength and TSR Improved TSR after long-term aging of the mixtures.
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10 participate in the project. Assistance in identifying candidate pavements was also sought from WMA industry groups, including contractors, equipment manufacturers, and additive suppliers.
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11 Authors Year Aging Stages Laboratory Tests Conclusions Bell et al. 1994 LTOAs (4 days at 212°F and 8 days at 185°F)
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12 former Aspha-min® product) , Astec DBG®, Aquablack™, EvothermDAT™, Sasobit®, and Terex®.
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13 mix design stage was based primarily on TSR using AASHTO T 283 or the HWTT. Only two agencies indicated using the Immersion-Compression Test (AASHTO T 165)
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14 especially when including crumb-rubber modified asphalt. The responses also indicated that the purpose of using WMA in 85 to 90 percent of the pavements built with WMA was to achieve temperature reduction.
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15 technologies ranged between 260 and 285°F (127 and 141°C) with higher temperatures sometimes required when crumbrubber asphalt was incorporated in the mixture.
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