Moisture Sensitivity of Asphalt Pavements (2003)

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178 TOPIC 4 Questions and Answers JON EPPS Granite Construction, Speaker ERIC BERGER Chemical Lime, Speaker JAMES ANAGNOS Akzo Nobel Asphalt, Speaker Q1—Pat Lavin, Arr-Maz What is the purpose of marinating the lime? A—Eric Berger Most commonly, it is used to react with the undesirable surface stuff, surface coatings, be they fine particles that it can often carbonate or clay with which it can react pozzolanically. In the case of granitic and other quarried stones, it just seems to provide better performance in some circumstances. The state of Nevada did quite a bit of work on this several years ago, and I think you did quite a bit of it, didn’t you, Jon, where they compared by testing behind the paver whether marination of a dry lime on damp aggregate process, not a slurried process, improved the performance? They concluded that yes, indeed, it did. In a later study that Peter Sebaaly did comparing the different application methods, NDOT decided that they’d stick to the marination method that worked best for them. But the study noted that in about 80% of the circumstances, the data indicated it didn’t really matter that much whether you marinated or didn’t marinate. Q2—Pat Lavin, Arr-Maz So the different time frames like 30 days or 3 weeks or 6 weeks are really indifferent? A—Eric Berger For how long you could leave it in stockpile? Q3—Pat Lavin, Arr-Maz For how long are you supposed to marinate it before you can use it? A—Eric Berger Usually that’s 24 to 48 hours before you can put it in the plant. That varies by the state that requires marination. In terms of leaving it in the stockpile, there have been a couple of studies done. Dallas Little did one in Mississippi a good number of years ago. Dr. Robin Graves, who’s in the audience here, did one probably 10 years ago or so. They discovered that in stockpile, it could remain active; the calcium hydroxide will remain chemically active for months.

Epps, Berger, and Anagnos 179 A—Jon Epps Those data are contained in the paper, too, about the stockpile. The carbonation takes place in the stockpile from the outside in and shows the depths of carbonation for various lengths of storage time that Robin Graves did. The other thing I might mention, and Dean can speak up if he wants. The most effective use of the marination process seems to be with those aggregates that contain some clay in them and gave enough time for the ion exchange to take place, which is pretty instantaneous if you can get the clay to the lime and then maybe it will have a pozzolanic reaction. And a little water. Q4—Larry Santucci, University of California, Berkeley This is a question for Eric and maybe a question some folks here from Caltrans might ask. On the chart that you showed toward the end of your presentation on cost savings using lime, could you explain why California is spending $30 per square yard while Colorado appears to be spending only $5 per square yard on projects? A—Eric Berger I don’t even have to bother Gary, the author of that study, with that because I worked for the state of Washington for a decade or 15 years, and the differences depend upon which costs are captured in a state’s reconstruction or maintenance activities. Wouldn’t you say that that’s true and different states report very differently, which is one of the reasons why it is so hard to transfer a PMS program from one state to another? I am sure that is what the cost difference is. Q5—Larry Santucci So this is not an apples-to-apples comparison of costs? A—Eric Berger It is data generated by each state for each state. But if you wanted to compare South Carolina with Colorado, it probably would be inappropriate because there are guardrails in one and shoulder widening in the other. Q6—Gayle King, Koch Pavement Solutions Based upon research by Bishara and Fager at Kansas DOT and reports from Ludo Zanzotto at Calgary, there appear to be serious incompatibilities between certain asphalt modifiers. In particular, one might boost a binder’s PG grade with acidic materials while at the same time adding basic components to the mix as antistripping agents. The problem is primarily communication. The binder supplier modifies the PG grade, but the contractor chooses the antistrip solution. In response to problems observed in Oklahoma and elsewhere, Nebraska just published a specification that requires binder suppliers to add liquid amines at their terminal before the binder is graded, so that grade fallback and modifier incompatibility can be avoided. Any thoughts on whether that’s an appropriate solution, or are there other ways to avoid compatibility problems? A—Jon Epps Is that a question, Gayle, or a statement?

180 Moisture Sensitivity of Asphalt Pavements: A National Seminar Q7—Gayle King I’d like to hear what others might suggest as a solution. How should we handle such incompatibility issues? A—Jon Epps I’ll just start out by saying that some public agencies require sampling the asphalt binder in the feed line to the mixing chamber, and so whatever goes on before that is the contractor’s and supplier’s responsibility. That forces the issue just like you are suggesting. Jim, do you have a comment? Eric? A—Eric Berger My response to that is one test is worth a thousand expert opinions. A—Jim Anagnos I think so far we have had this occur several times in the state of Texas with particular suppliers and basically the liquids are added at the contractor’s point in that state, at the contractor on site. The thing that he has addressed, the problem at that point, he has changed suppliers of the binder. I’m not saying that is the solution to it, but those are some of the things that have been done. I guess the biggest solution to it would be to have it added at the refinery and allow the folks at the refinery to have that worked in. Sometimes you can add concentrated amounts of amines, particular kinds of amines; it is my understanding that will combat that. You’re going to ask me how much that is. I can’t answer. I don’t know. Q8—Pat Lavin, Arr-Maz I think what Gayle is specifically talking about is the state of Kansas has developed a specification where they don’t like the idea of using phosphoric acid to bump the grade of their asphalt binders. So what they are doing is they are requiring the asphalt supplier to prequalify their binder with amine antistrip additive as a way to test for the presence of phosphoric acid in the asphalt. What we’ve found out is it is also crude sensitive. In other words, one supplier will knock it down a grade and another supplier won’t. Q9—Bob Humer, Asphalt Institute Jon, in one of your slides, there is a polymeric treatment of aggregates and it says 1 pound per ton, which is like 5/100th of a percent. In what form is that and how do you really treat that entire aggregate surface with 1 pound of polymeric materials? Just give me a picture of how this works. A—Jon Epps Very carefully, obviously, is the answer to that. Peter, do you want to respond to that? Peter Sebaaly is in the audience and he was the everyday person on that study. A—Peter Sebaaly, University of Nevada, Reno Yes, the 1 pound per ton is a true figure. You dilute the material. It is a very thin material and you dilute it with water and very, very, very carefully you mix it in the lab. That’s all I can say.

Epps, Berger, and Anagnos 181 Q10—Bob Humer, Asphalt Institute Just a comment, Eric. You said that mixing lime with asphalt is still in kind of a trial stage. On reservoirs, such as for drinking water, we like to see a coating of mastic, which is specified as a blend of paving grade asphalt and 70% by weight lime. Sometimes that is a little hard to blend, so they drop off to 60% lime. So we are at pretty high concentrations of blending lime in with asphalt for those mastic coatings. Just that you are aware of that. A good example is the MWD Devil’s Canyon Afterbay reservoir near San Bernardino. A—Eric Berger One of the problems that we’ve had, and this is being worked on both here in the U.S. as well as in Europe, is the volume that we can blend in at the time just as you described. Dallas Little and Chemical Lime and the Arizona DOT are sort of struggling their way to a field trial of this very thing. But it certainly would simplify matters for everyone and do a world of good for a lot of bitumens, I think. Q11—Barry Baughman, Ultrapave I’d like to address the polymer issue. It is 1 pound of dry polymer per ton of aggregate. Basically, the material is supplied as a latex, which has very small particles and very large surface areas. They are applied on the belt as the aggregate goes down into the drum dryer. During the first few feet in the drum dryer, they get dispersed throughout the aggregate. They form a waterproof coating onto the aggregate. Basically, the aggregate (which is water loving) becomes water repelling. The material we use is also a hydrocarbon polymer; therefore, it has an attraction to the asphalt and improves or enhances the bond to the asphalt. If anyone has any questions, they can see me. Q12—Ron Sekhon, Caltrans What is the chemical composition of these liquid antistrips? With lime we have some sort of information how the reaction takes place with the clay particles and so forth. I was interested in knowing how the liquid antistrip works. A—Jim Anagnos If you want the chemical composition, you’re not going to get that from me because I don’t know what it is. You might have to ask the chemists who are involved like companies like Arr- Maz, Akzo Nobel, Unichem, Rohm & Haas. Those chemists might be able to divulge that kind of information. I cannot. Q13—Jack Van Kirk, Basic Resources, Inc. One of the things that we’re really toiling with in California, we have for many years, is liquids versus lime. There have been a lot of studies done, and I know in the early years certain types of liquids came out that were used and weren’t quite as effective. Later on, I guess a new line of liquids came out and one of the things that is very difficult for a lot of us in the audience to do when we look at these studies is you look at the lime folks and they show the lime is great and the liquid is not. You look the other way and you find the liquid is just as good as the lime in different ways. One of the things that would be very helpful to us is to look at some type of study that you showed earlier and I think it indicates that when you use a liquid it makes a big difference in the kind of liquid you use on the type of aggregate you have. So, the question is,

182 Moisture Sensitivity of Asphalt Pavements: A National Seminar when the lime studies were done, are we looking at apples and oranges? Are we looking at the same types of things that they are looking at today—like you talked about a high-quality liquid as opposed to some of the things that were looked at early on? It is like the white industry versus the black industry when it comes to pavements. It is the same thing for lime versus liquids. If we are going to be able to move forward with this in an equal type of evaluation, we have to be looking at the same types of products in both cases and we all know that lime works very well. The bottom-line question is, is there a difference today with the liquids that are being done that are going to give us the same type of performance as maybe dry lime to wet aggregate or even the lime slurrying in some cases and were they different in some of the cases that were done in the lime industry? A—Jim Anagnos I know, for example, for some of the experimental work we did at the University of Texas between 1970 up to 1990 that I was involved with—I know at that time we used an awful lot of liquids that were not very good performers. And I suspect, I don’t have absolute data on it, I just know from my own experience that we used additives that were not good performers. I don’t know what the studies would have shown back then if you had used a high-performance additive and whether they were available at that time. I can’t answer. I don’t know. But I have a feeling that a lot of the studies were done with inferior products. For example, in Virginia, I think Bill Maupin looked at a study early on in the early 1990s of some projects that were placed and he found that the liquid did not perform well. So, he raised his specifications, his requirements, and he went back out and looked at projects under the new requirements and found that they were not any different. He could not see any discernible difference between the liquids and the hydrated lime. What I am leading up to is I guess you have to have some sort of testing process to look at these things. This is a very complicated situation. I didn’t get to say this earlier, but I don’t think that you have an elixir of an additive that can be added to anything and everything and have it accomplish everything under the sun. I don’t think that’s possible. I don’t think you’re going to ever find it. I don’t know that you’re ever going to find a particular test that’s going to be 100% positive each time. I say positive, that it will relate to field performance. When you look at field performance you have many other issues involved besides “what kind of additive did you put in,” so that’s a very hard correlation to make. A—Jon Epps Just an observation from reviewing the literature once again, Jack. It’s not an answer to your question. The various types of additives that we’ve talked about today are certainly asphalt binder dependents. It’s been said already they’re aggregate dependent, their concentration dependent, and they are also test method dependent in terms of how good they show up to be. That’s as a minimum that I found out. Q14—Mike Cook, Caltrans Two quick questions. We had some discussion about marination of lime-treated aggregate and the maximum marination period allowed. Does environment like rain affect that maximum marination period? My second question is how do we know what a high-quality liquid antistrip is? Is there any ASTM or AASHTO designation or a reference to differentiate between antistrips that perform well and those that perform poorly?

Epps, Berger, and Anagnos 183 A—Eric Berger The answer is that I don’t remember in Robin Graves’ study, but I do remember in the study that Dallas Little did in Mississippi that during the 6 months or so that the material sat in stockpile, it rained at least 8 inches. What happened was that the carbonation, which for those of you who don’t know is the retransformation of the calcium hydroxide into calcium carbonate or limestone, proceeded from the outside surface of the stockpile just a couple of inches into the stockpile. The calcium hydroxide was active on the inside of the stockpile. It seems to me Robin’s study went at least that long, and did it rain much in that study? A—Robin Graves Yes. A—Eric Berger He said yes. A—Jon Epps And it was for over 120 days, Robin, or something like that? A—Robin Graves About 6 months. A—Jon Epps Jim, can you answer the next question, which dealt with how do you tell the liquid antistrips that perform well from those that perform poorly? A—Jim Anagnos The only way I know to do it is by doing some additional testing. For example, you might use a Hamburg-type test, you might use a PG grading-type SHRP-type test to see what that additive is doing to your neat binder. But I think it all comes down to what you are doing for testing. Is there something in AASHTO or ASTM that this qualifies one as being a “good one or a bad one”? I don’t know of any.

TOPIC 5 Material Production, Mix Design, and Pavement Design Effects on Moisture Damage