More and more attention has been paid recently to hot mix asphalt pavement surface characteristics. In addition to structural capacity and durability, it is now desirable to design pavements to meet noise, texture, friction, and ride requirements. Noise (both interior and roadside) is at the forefront of the minds of both pavement designers and the traveling public. Many studies are currently underway around the United States and in Europe to address noise and these other issues.
The traditional way to reduce noise for nearby residents and businesses has been to build noise walls. Besides being large and undesirable to look at, noise walls can also be quite expensive. Innovative pavement surfaces have recently been developed as an alternative to building noise walls. The type of wearing course plays a major role in determining the surface characteristics of a pavement. Several options that can provide lower noise levels than conventional dense-graded pavements include stone matrix asphalt (SMA), open graded friction course (OGFC), porous HMA, 4.75-mm Superpave mixes, and NovaChip. In general pavements with smaller maximum aggregate size, open gradation, and negative macrotexture produce less noise.
SMA and OGFC pavements have been used extensively in the southern United States with great success. However, far fewer states in cold climates have used these open-textured mixes. As a result little is know about the performance of open-textured mixes in cold climates. There is a fear that over the harsh winter the pavement will disintegrate due to sand and salt operations, freeze-thaw action, snow plowing operations, and the like. There is a need to conduct a controlled experiment in a northern state like Minnesota to determine the durability and performance of a pavement built for certain surface characteristics. MnROAD offers an experimental site where the risk can be taken to construct and monitor open-texture mixes in a cold environment.
Related studies include:
. TPF 962: Pavement Surface Properties Consortium: A Research Program (Virginia)
. NCHRP 1-44: Measuring Tire-Pavement Noise at the Source (Illingworth & Rodkin, Inc.)
. NCHRP 1-43: Guide for Pavement Friction (ERES)
. NCHRP 9-41: Performance and Maintenance of Permeable Friction Courses (NCAT)
. TPF-5(107): Refinement and Field Validation of Mix Design Criteria for 4.75 mm Superpave Mixes (Alabama)
The TPF 962 study mentioned above is meant to serve mainly the Eastern United States. The research proposed in this work could be seen as a parallel research study for the Upper Midwest. MnROAD provides a unique opportunity to measure surface characteristics of a variety of HMA pavements with various pieces of equipment in a safe and controlled environment. This research also serves as an extension/validation of several of the current NCHRP studies. The findings relating to measuring noise and frictional characteristics could be validated with a field study at MnROAD. Finally, several surface courses designed for noise and other surface characteristics (SMA, OGFC, 4.75-mm Superpave, porous HMA), have been used extensively in the South, but this project would provide a good opportunity to place these mixtures in a cold climate to validate their performance.
This research project could progress on two tracks:
. Construct two new HMA pavements using SMA, 4.75-mm Superpave mix, etc. specifically for the purpose of reducing the noise while maintaining other important surface characteristics.
. Monitor all of the new test cells built at MnROAD for their noise, texture, friction, and ride characteristics.
This pooled fund study is strictly to perform the surface characteristics research on newly built test sections at MnROAD, and its funding will come from Mn/DOT and other participating states. The funding for the construction of new test sections will be obtained separately from Mn/DOT and other partners.
Scope of Work
This project is expected to consist of the following activities:
. Work Plan: The work plan for this pooled fund study will be developed by the participating organizations. Partners from other cold climate states can bring their own experiences to the table. Part of this plan will include the decision whether to build two new sections at MnROAD with a pavement surface specifically designed to reduce noise or to simply monitor the existing test sections.
. General Testing & Monitoring: Monitor the pavement performance over time on each test section using standard practices. Monitoring activities will include FWD tests, rutting measurements, distress surveys, ride measurements, and analysis of pavement sensor data.
. Special Testing & Monitoring: Monitor the noise readings (NCAT trailer, close proximity, and roadside measurements), texture measurements (circular texture meter), and friction measurements (FHWA skid trailer) as needed throughout the study.
. Noise Modeling & Validation: Apply the findings of this study to current noise modeling software (TNM, MINNOISE, etc.).
. Pooled Fund Travel: Money for each state to travel to discuss the progress of the study.
. Data Analysis & Reports: Work done under a research contract will develop interim and final reports that document the findings of this study.
Mn/DOT along with other participating states are asked to contribute $15,000 per year for 5 years to fund the research proposed in this pooled fund study.
The Minnesota Department of Transportation (as the lead agency) along with other partners will provide approximately $200,000 in construction funding outside of this pooled fund study to construct the pavement test sections mindful to certain surface characteristics.