It is well known that having adequate and uniform asphalt mixture compaction is critical for pavement life. Multiple studies have estimated that a 1% decrease in density can reduce pavement life by approximately 10%. Currently, a target compaction density is widely used for asphalt mixture compaction acceptance. However, common quality control and acceptance practices for density reply on randomly checking density with nuclear density gauges or cores taken on spot locations. This approach is labor intensive and provide limited information on overall pavement compaction quality, many times missing insufficiently compacted areas. Research conducted by the 2nd Strategic Highway Research Program (SHRP2) R06C has demonstrated a breaking new technology, where a DPS system can be used for routine operation to evaluate density and uniformity of asphalt mixture compaction with continuous pavement coverage of the entire pavement area. As part of SHRP2 R06C, several state DOTs have evaluated a particular Ground Penetrating-Radar (GPR) DPS system, called the Rolling Density Meter (RDM) with overall, very promising results. A calibration method for the RDM system has been developed and recommended. In addition, a probability histogram of measured dielectric constant is found to be an effective tool for assessing pavement compaction quality and uniformity. Based on this evaluation, state DOTs have found that the system can be used for compaction assessment of essentially the entire pavement area as part of Quality Assurance. However, some additional research and improvements are still needed to use DPS systems for acceptance.

The objective of the proposed pooled-fund project is to establish a research consortium focused on A) further advancing and improving the system based on experience and needs from participants so that the system can effectively and efficiently support their Quality Assurance Programs; B) support communication; C) provide training and technical assistance that includes providing support for specification development and strategies for agency full implementation; and D) conduct technology promotion and marketing for the system. Specific tasks within this multi-year program will be developed in cooperation with the consortium participants.

The work plan will be developed based on the priorities indicted by the consortium participants during the kick-off meeting. While the details and scope of the objectives will be further defined to reflect the concerns of the consortium participants, it is anticipated that the project will include the following: A). Further Advance and Improving the System 1. Development and implementation of a real-time warning mechanism to inform DPS users of a system error during the data collection process. 2. Development of an AASHTO standard for equipment and operator certifications. Develop a detailed workplan. The workplan should, at minimum include the following: a. Experimental design of testing matrix. b. Identify test location(s). c. Coordination with participating agencies. d. Perform necessary tests to develop an equipment and operator certification procedure. e. Draft an AASHTO standard for equipment and operator certification (similar to AASHTO R56). 3. Conduct a round robin test among the agencies that have the system and develop equipment precision and bias statements and testing methods: Develop a detailed workplan for a round robin test. The workplan should, at minimum include the following: a. Contact the states that have DPS equipment. b. Coordinate with the states to gather all the equipment together. i. Each agency’s operator also needs to travel to the identified test location. c. Perform verification of all the equipment using manufacture provided calibration/verification materials. d. Conduct necessary tests following the workplan. (ASTM E691 “Standard Practice for Conducting an Inter-laboratory Study to Determine the Precision” can be used as a guidance). e. Perform data analysis. f. Establish precision and bias. 4. Develop AASHTO specification on data collection protocols and analysis method. This task should, at minimum, include the following: Data Collection a. Develop specifications on i. HMA mat temperature requirement. ii. Best time for data collection, data collection speed; sampling frequency and distance from the finish roller. iii. Maximum and minimum HMA lift thickness. iv. The number of data collection passes needed in order to assess compaction quality of the full lane width? v. Data collection pattern and location based on different construction traffic control methods (for example: full closure vs moving traffic control) and what we want to know and how to use the results (for example: joint assessment vs only mat assessment). vi. Develop equipment error reporting procedures. b. Develop equipment verification procedure in field including i. Transverse profile (perpendicular to traffic direction) method ii. Swerving profile method. Data Analysis a. Perform data analysis and develop criteria that can be implemented for HMA compaction acceptance in terms of both uniformity and density based on how the results will be used (joint vs mat). The criteria should include both histogram and percent conforming methods. Develop a draft AASHTO specification on data collection and analysis. B). Support Communication a. Semi-annual User Group Webinars. b. Annual Face-to-Face User Group Meetings including invitational travel. c. Quarterly Conference call Updates with Interested Parties if necessary. d. Quarterly Conference call with a Technical Advisory Team. e. WEBSITE Establishment and Maintenance. f. Support AASHTO and ASTM specification development, improvement and refinement. C). Provide Training and Technical Assistance. 1. More detailed hands-on training on set up, calibration and operation; 2. Training on implementation strategies by an agency; 3. Executive level training; 4. Webinar training, help participants on training development, on-call technical assistance, etc. 5. If needed, provide support to participating agencies in specification development. D. Promote the technology through technology prom

This project is expected to have a minimum participation of at least five agency members (including FHWA). Minimum annual commitment of $25,000 per year per agency for three years within CY2019-2021.