Moisture Sensitivity of Asphalt Pavements (2003)

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317 SUMMARY REPORT: BREAKOUT SESSION 4 Construction and Field Performance G. W. MAUPIN, JR. Cochair Virginia Transportation Research Council JOE PETERSON Cochair California Department of Transportation STEVE HEALOW Note Keeper Federal Highway Administration This session was convened by facilitators Bill Maupin and Joe Peterson, with Steve Healow as recorder. After 30 minutes of enumerating discussion topics, the group began preparing its presentation in earnest by focusing on best construction practices that experience has shown will help control moisture problems. We also wanted to focus on the real-time information that is useful for making better decisions during construction that are effective in preventing moisture- related distress. Similarly, we reviewed best practices at the hot-mix plant, which could preclude moisture damage. The following assumptions were adopted to exert some control on our free-ranging discussions: • Good contract administration practices (by the agency and contractor and producer) are in place. • We have a good asphalt concrete mix design. • Our materials meet specifications (i.e., good, clean aggregates and good binder). • Our supplier has good quarry practices. • We have a good performance-based testing program in place. BEST PRACTICES The following best practices for minimizing moisture sensitivity during construction were identified by members in attendance: • Training: All team members (agency and contractor) need standardized training. This is discussed later in the section on identifying gaps and barriers and is a milestone in the strategic plan. • Materials handling: Aggregate moisture content, aggregate segregation, and temperature segregation are the most critical elements. If they can be controlled, then materials handling will be all but eliminated as a contributing factor.

318 Moisture Sensitivity of Asphalt Pavements: A National Seminar • Production balance and control: For hot-mix plants with continuous drum mixers, the plant operator must adjust for moisture in the aggregate. Out on the grade, we must adjust for some balance between plant production, the speed of the paver, the roller pattern to achieve target density, the number of trucks, the haul distance, and other critical factors. • Uniform optimum mat and joint density: If we could consistently accomplish this, most of our moisture sensitivity problems would go away. • Proper drainage at the surface and subsurface: Let’s not ignore the fact that years after new construction, we have additional opportunities to restore proper surface drainage, that is, with maintenance treatments and rehabilitation projects. • Preplanning: Before construction begins, it is important to assign responsibilities, establish who is responsible for what, and clearly define roles and avenues of communication. IDENTIFY GAPS AND BARRIERS The only items standing between us and resolving of the moisture sensitivity problem are these issues: • We are in crisis mode for training as a result of personnel turnover in agencies and industry. Thus, inviting a mix of agency and industry people to our training sessions takes on new significance. With similar backgrounds, all are more likely to emerge with a cooperative spirit, which will pay dividends by resolving construction issues at the local level. We help ourselves by taking advantage of this valuable opportunity to foster networking. • Many of us struggle with a time lag in process control. Timely results from materials testing are invaluable to the owner and contractor. However, their value diminishes rapidly over time. • Lack of continuous test results means lapses occur in our process control. It is like dozing off during an exam. • In regard to complexity of project logistics, our construction projects tend to succeed when our materials suppliers deliver the goods, within specified limits, when and where they are needed, regardless of whether or not the materials are time sensitive. Our successful contractors cope every day with a maelstrom of risks and resources to construct the final products as specified. Why can’t all suppliers and contractors succeed? How is it that some are consistently successful and make it appear easy? • We will need accurate density measurements to achieve target density in a cost- effective manner. • Equipment constraints, which are often overlooked, contribute significantly to a design that is constructible and a project free of delays, change orders, and cost overruns due to rejected work. • Agency managers’ note: Project control by funding is a recipe for disaster. The practice of downsizing projects in final design or after they have gone to construction is a recipe for failure. IDENTIFY RESEARCH NEEDS • Continuous measurements of density or stiffness would provide the roller operators with continuous feedback on the sufficiency of their rolling pattern.

Maupin, Peterson, and Healow 319 • Real-time automated plant control is an idea whose time came long ago, but which our industry has only partially embraced. Consider the Boeing 747. Life is much easier for the pilots as a result of the higher degree of automation at the controls. They choose to fly hands-on at takeoff and landing, although the aircraft avionics and programmable navigation systems have been sophisticated enough for decades to proceed hands-off from gate to gate. Our hot-mix plant operators deserve more of that type of automation, in which the menial tasks are automated, leaving them free to monitor and adjust as necessary. • Similarly, our people and projects will benefit immeasurably from automated paver control and feedback. • What are the effects of temperature on adhesion and, in turn, on the potential for moisture damage? • What is the relationship between permeability and performance? ELEMENTS OF A STRATEGIC PLAN • Development and implementation of joint training courses with the following features: self-directed learning, understanding basic materials, and virtual training for equipment operators • Preconstruction partnering in which roles are defined, responsibilities are assigned, and authority is delegated • Construction activities that focus on control of segregation Adopt standard definition of segregation (i.e., NCHRP) Adopt accurate measurement standards Adopt specifications with incentives and disincentives to achieve desired results • Balance construction activities Implement best practices Submit productivity plan Implement productivity plan • Obtain uniform optimum density Optimize joint density Adopt accurate measurement tool Adopt incentives and disincentives to obtain desired results