Moisture Sensitivity of Asphalt Pavements (2003)

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276 TOPIC 9 Questions and Answers JAMES MOULTHROP Fugro-BRE, Speaker Q1—Gayle King, Koch Pavement Solutions One might perceive a division here into pro-Hamburg and pro-T283 camps. I hope everyone will read Tim Aschenbrener’s CDOT reports and remember how he has used both tests in tandem. Tim has made great use of the Hamburg as a research tool to understand materials, as a forensic tool to evaluate premature stripping failures, and as a performance tool to award project bonuses. However, he has adapted T283 for daily specification control and relies on methylene blue to control clay. Of course, Dale Rand has taken the very big step of adopting Hamburg for all hot- mix specifications, but only after testing some 1,500 mixes to set performance limits and understand local materials. Let’s put their findings and actions into perspective as it relates to Caltrans. The key decisions: $4.00 a ton to slurry lime, $2.00 a ton to use dry lime, $0.50 a ton for liquid antistrip or no additive for moisture resistance. That’s up to $10 million to be spent on somewhat arbitrary decisions lacking best available information. If clay is the bad actor, methylene blue and Hamburg should be part of the decision process as to best practice, as Aschenbrener so clearly demonstrated when he used both to locate clay seams in a problem aggregate pit. If high clay content is the only reason to slurry lime, then methylene blue could serve as the single specification control to make that decision once relative damage risk is understood in the Hamburg. One other valuable reason to bring a Hamburg into Caltrans labs may be more political than scientific. Categorize this idea as a picture worth a thousand words. When a contractor is required to employ a more expensive alternative than a competitor’s, serious heartburn ensues. Watching his favorite mix fall apart under the Hamburg wheel leaves an image that causes him not only to understand the problem, but makes him want to do better. Most important, he now has a tool, which enables him to isolate and resolve his own quality problems. There are many things that Caltrans can learn from the Hamburg that don’t require changing specifications. Let’s try not to divide into two camps, but recognize where both T283 and wet wheel-tracking tests can provide best value. Q2—Tim Aschenbrener, Colorado Department of Transportation A couple of comments. One, it would be a value to me, very soon if possible, if I could get a copy of the presentations that were done this morning. I don’t know if that’s something you can e-mail out to all the participants, because that is something I can start taking a look at and sharing with the folks back in Colorado right away. A—Gary Hicks, MACTEC I’ve instructed Dr. Leahy to get those out so they’ll be out either tomorrow or early next week, depending on what else she has to do.

Moulthrop, Button, and Hejl 277 Q3—Tim Aschenbrener, Colorado Department of Transportation A second thing: you mentioned a survey. I am wondering who the target audience for that survey would be. One audience might be all the states in the country 6 to 8 months from now. I’m not sure if that would really be the right audience. I might be curious if we surveyed all the people here, not just the people from Caltrans, but everybody here 1 year from now. Have you done anything differently? Changed a specification? Written a research problem statement? What have you done differently in the last year as a result of this? It wouldn’t have to be a meeting. It could be a simple survey, and I’d be interested in one or two paragraphs or one or two pages written up about some of the things that happened as a result. A—Jim Moulthrop That is very doable and I think it is a very good idea. Q4—Carl Monismith, University of California, Berkeley I would like to just make a comment about Gayle King’s comment. I don’t believe that the discussions that took place will lead people to select this camp or that. If they have the information, they will make their own judgments. For example, the discussions we had yesterday in the session on tests and treatments were very healthy, particularly those related to tests. I would hope that Eric Berger, the cochairman of the session, would agree with me on this assessment.

SUMMARY REPORT: BREAKOUT SESSION 1 Fundamentals