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WESTERN REGIONAL SUPERPAVE
CENTER
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Evaluation of Physical Properties of Nevada's HMA Mixtures This project has been funded by NDOT since 1991 to present. The objective of this project is to use AASHTO T-283 to evaluate the moisture sensitivity of NDOT's HMA mixtures. The research is being conducted at the Pavements/Materials Laboratory of the University of Nevada (UNR) under the direction of Drs. Sebaaly and Epps (until 1997). Every year NDOT provides the UNR laboratory with samples of HMA mixtures from approximately forty construction projects. The samples include both the laboratory prepared and field prepared mixtures. The laboratory mixtures are the ones prepared during the mix design process while the field mixtures are obtained during the paving operations. The UNR researchers evaluate the tensile strength and resilient modulus properties of the mixtures at the dry and moisture conditioned stages. The AASHTO T-283 with one freeze/thaw cycle is used to moisture conditioned the samples. Over the past five years, this research has developed a large database of dry and moisture conditioned mixtures properties for over two hundred field projects. These projects use various asphalt binders, aggregate types and gradations. In addition, some of these projects are located in southern Nevada where the environment is hot-dry while others are located in northern Nevada under a cold-wet environment. The field performance of all projects has been documented as part of NDOT's PMS. The major usage of this database has been the development and implementation of specifications for moisture sensitivity of NDOT's HMA mixtures. Each year, NDOT's Materials Division and the UNR researchers evaluate the additional data and monitor the performance of the mixtures as compared to the specification limits. Based on this comparison a decision is made whether to change the specification limits or to maintain them at their current level. Available Information: Copies of research reports can be obtained by contacting WRSC.
NCHRP 9-13:Evaluation of Moisture Sensitivity Tests This NCHRP project was completed by the research team of the University of Nevada (Drs. Eps and Sebaaly) in 1999. The objective of this NCHRP project is to evaluate the applicability of AASHTO T-283 moisture sensitivity test with the Superpave mix design procedure. The research evaluated the impact of the following factors on the results and recommendations of AASHTO T-283 test. Aggregate Source: 5 Compaction Method: 4 Loose Mixture Aging: 4 Compacted Mixture Aging: 2 Saturation Level: 3 Freeze/Thaw Cycle: 2 A factorial laboratory experiment was conducted which measured the tensile strength and resilient modulus properties of the AC mixtures at the dry and moisture conditioned stages. In access of 3000 AC samples were tested. The data from the laboratory experiment are currently being analyzed and the findings will be readily available to this project. It is expected that recommendations will be made concerning some modifications of the AASHTO T-283 method and the necessary steps that state highway agencies must take in order to incorporate AASHTO T-283 into their Superpave mix design process. Available Information: NCHRP Report 444 Other reports are available on a CD from NCHRP
Evaluation of New Generation of Antistripping Additives: This project was completed in 1991 with an objective to evaluate the effectiveness of lime as compared to other antistripping additives in reducing the moisture sensitivity of HMA mixtures. The AASHTO T-283 test with one freeze/thaw cycle was used to assess the moisture sensitivity of HMA mixtures made with two types of aggregates and three types of antistripping additives. Each antistripping additive was used at three levels. The measured physical properties of the mixtures included the dry and wet resilient modulus and tensile strength. Available Information: Report can be obtained by contacting WRSC.
Evaluation of Ultracote Polymeric Aggregate Treatment System: This project was completed in 1997 with an objective to compare the performance of the Ultracote polymeric system with lime in reducing the moisture sensitivity of two Nevada’s aggregates. The two aggregates were selected to represent a low and a high moisture sensitivity. The AASHTO T-283 test was used to evaluate the AC mixtures’s resistance to moisture damage. The laboratory data indicated that the Ultracote system can be as effective as lime on highly moisture sensitive aggregates if the appropriate percentage is used. Available Information: Report can be obtained by contacting WRSC.
Evaluation of the Effectiveness of Lime in HMA Mixtures. This project was sponsored by the Nevada DOT and completed in 2000. The objective of the project was to evaluate the effectiveness of lime in reducing the moisture susceptibility of in-service pavements. Several lime-treated and untreated pavements sections were identified and evaluated in terms of their mechanical properties and long term performance. Multiple freeze-thaw testing was used to evaluate the mechanical properties of mixtures from the between wheel-path and the wheel path of treated and untreated mixtures. The NDOT PMS data were used to evaluate the impact of lime on the long-term performance. The study showed that lime has been effective in reducing the moisture susceptibility of Nevada’s mixtures. The reduction in moisture susceptibility translated into a 33% extension in the performance life of the pavement which compares very favorably with the percent increase in the cost of HMA mixtures of 12% due to lime treatment. Available Information: Synthesis can be obtained by contacting WRSC.
Effect of Lime on The Moisture Sensitivity of AC Mixtures with California Aggregates This project was completed in 1992 with an objective to evaluate the effectiveness of lime on improving the moisture sensitivity of HMA mixtures made with two California aggregates. The AASHTO T-283 test with one freeze/thaw cycle was used to evaluate the moisture sensitivity of the HMA mixtures. Three percentages of lime were used with each type of aggregate. The physical properties of the mixtures included the wet and dry resilient modulus and tensile strength. Available Information: Final report can be obtained by contacting WRSC
Asphalt Concrete Anti-Stripping Techniques This on-going research project is sponsored by the South Dakota DOT. The overall objective of the project is to evaluate the effectiveness of anti-stripping additives in reducing the moisture damage of HMA mixtures. The research is evaluating the best method of adding lime to HMA mixtures to minimize personnel exposure and environmental impact, determine the effectiveness of anti-stripping additives and develop guidelines for future use of anti-stripping additives in South Dakota. The project will be conducted between October 1999 and October 2002. During the summer of 2000, the project constructed twelve test sections in South Dakota with various anti-stripping additives and is currently evaluating the mechanical properties of the various mixtures and the field performance of the sections. Available Information: Download Final Report "Asphalt Concrete Anti-Stripping Techniques" Download Executive Report "Asphalt Concrete Anti-Stripping Techniques"
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