Moisture Sensitivity of Asphalt Pavements (2003)

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256 TOPIC 7 Questions and Answers AMY EPPS MARTIN Texas A&M University, Speaker DALE RAND Texas Department of Transportation, Speaker DEAN WEITZEL DARREN TEDFORD Nevada Department of Transportation, Speaker PETER SEBAALY University of Nevada, Reno, Speaker LEROSE LANE California Department of Transportation, Speaker G. W. MAUPIN, JR. Virginia Transportation Research Council, Speaker Q1—Tim Aschenbrener, Colorado Department of Transportation Question, I guess for Dale from Texas. I see that you’ve indicated that AASHTO T283 is highly variable and has poor reproducibility. I was wondering, how did you quantify that? A—Dale Rand I might have to refer this one to Mansour. Actually, I think he did the study on this one. I don’t know if you want to try and address this. We’ve done some studies both in-house doing proficiency testing and preparing samples, sending them out to folks and getting results that were all over the board. We did a formal study that Mansour headed up that came to that same conclusion, that the test was highly variable. The multiple lab variability was high and our experiences have shown us that on projects. The contractor results passed with 95 TSR and then the district tests it and it’s a 70 TSR. We referee test it and get an 80 TSR, and we all do it again and we do it a few more times. Q2—Tim Aschenbrener, Colorado Department of Transportation And I had a follow-up comment for Caltrans as they are going through an implementation process. I appreciate seeing the matrix there and I would offer just one word of caution regarding doing your round-robin. If the results of the round-robin are not reasonable, it appears you might go back to status quo. I would offer an experience from Colorado. We have a quality assurance program, and in that program, we test all of our materials, whether asphalt, concrete, or soils, on a regular basis. Every round-robin is accompanied by a series of findings and recommendations. And probably very much like Texas found one year, the finding was that our version of the T283

Epps Martin, Rand, Weitzel, Tedford, Sebaaly, Lane, Bressette, and Maupin, Jr. 257 was not reproducible. I think that we had 33 labs participating—16 of those were DOT labs. The average TSR result was about 85, if I remember correctly, and the standard deviation was 15. As you look at the scatter through those 33 labs, the finding was how do we know if the material passes or fails? So the recommendation was that we needed to make improvements. So actually, it was over a 3-year time period that it took multiple round-robins to identify what boiled down to about three key elements of the test procedure that you have to pay really close attention to. And at our last round-robin, and I think we still have 33 labs participating, the standard deviation is now 5. I think that in terms of reproducibility, the concerns can be addressed. I also think it would be optimistic to believe that you could get good reproducibility the first time out of the chute, so to speak. So I would encourage at least a couple of iterations of round-robins and identifying the key items of the test procedure before going back to the status quo. Q3—Bob Humer, Asphalt Institute Dean, in your notes it says marinated, and I want clarity. Because I’m familiar with lime slurry marination, I want to make sure how it differs from that. A—Dean Weitzel When I use the term “marination,” I’m talking about the fact that we’re putting dry lime on wet aggregates and we stockpile it for 48 hours. To me, the marination is giving the lime time to affect the PI of the aggregate. The other procedure is you add water to the lime and you make a slurry and then you add that to the aggregate, and we’re not doing that. So when I use the term marination, it’s just giving it time in the stockpile to affect the PI. Q4—Dick Root, Root Pavement Technology Dean, I’m not trying to be an obstructionist, but I’m looking at your time marination study, particularly for your north aggregates. I think you told us that those are your high PI materials and therefore marination benefits them the most. And I am looking at 45 days, and I see one that meets your minimum criteria and all the others fail on the TSRs. I’m wondering, is 45 days too long and you’re out at 60? A—Dean Weitzel You know, what we’ve found was probably at 45 to 60. It really is an individual composition. We wanted to give the contractors enough time to get out there to crush and advance. I will tell you we handed that out to the contractors and we told them, our recommendation is you use it as fast after the 48 hours as you can. If you choose to go to 45 days or 60 and it fails, we’re going to get it behind the paver and you’re shut down. That’s not our problem. I’ll give them 120 days but when they fail, they’re going to get shut down. Q5—Dick Root, Root Pavement Technology I guess that would be the point. No requirement necessary. We’re going to test it as we use it. A—Dean Weitzel And we do. Like I say, we wanted to put a maximum because we didn’t want them to get out there in November, crush it, stockpile it, and then have it sit there till June. We’re just asking for a fight at that point in time. I will tell you, in the last 3 years, I can think of one instance where it went over the 60 days, even the 45 days. We don’t refuse to let them use it even if it goes over

258 Moisture Sensitivity of Asphalt Pavements: A National Seminar the 60 days. What we do then is add an additional % lime and retest it according to the AASHTO T283. We do the modified Lottman. If it passes, we let them use it. And so it’s not a total loss if it goes past that drop-dead date and you don’t get to use it. Q6—Mansour Solaimanian, Pennsylvania State University I just had a comment regarding what Tim mentioned on the repeatability and reproducibility of the AASHTO T283 and what he did for improvements. We looked at variability in Texas method 531-C, which in some ways is different from AASHTO T283 in regard to the vacuum saturation. In T283, you have 55% to 80% saturation, and in Tex 531-C, you conduct the saturation phase for 30 minutes. This creates some differences between the two methods.

TOPIC 8 Specifications to Control Moisture Sensitivity Problems in Asphalt Pavements