Russell Dabbs and Jon McCabe join Brian to discuss the most common nonconformities for liquid limit and plastic limit of soils and how to resolve them.
AASHTO re:source Q&A Podcast Transcript
Season 3, Episode 26: Top nonconformities on D4318, T89, and T90
Recorded: October 21, 2022
Released: November 1, 2022
Host: Brian Jonson, AASHTO Accreditation Program Manager, AASHTO re:source
Guest(s): Jon McCabe, Quality Analyst; Russell Dabbs, Senior Laboratory Assessor, AASHTO re:source
Note: Please reference AASHTO re:source and AASHTO Accreditation Program policies and procedures online for official guidance on this, and other topics.
Transcribed by Kim Swanson and MS Teams.
[Theme music fades in.]
[00:00:02] Announcer: Welcome to AASHTO resource Q & A. We're taking time to discuss construction materials, testing, and inspection with people in the know from exploring testing problems and solutions to laboratory best practices and quality management, we're covering topics important to you. Now here our host, Brian Jonson.
[00:00:20] Brian: Welcome to AASHTO re:source Q&A. I'm Brian Jonson and today on the podcast, we're going to get into a very technical subject matter that is going to be relevant for laboratories performing soil testing and with me to talk about this is Russell Dabbs from AASHTO re:source Russell, welcome to the podcast.
[00:00:43] Russell: Thank you, Brian. Good to be here.
[00:00:44] Brian: We had Russell on before to do a very similar episode, which I'm going to lay out here in a minute. Also joining us is Jon McCabe. Jon, we finally got you.
[00:00:56] Jon: Yep, finally got me on here.
[00:00:57] Brian: Yeah. So, Jon is one of the quality analysts and somehow, he's managed to avoid being a guest on the podcast for a while. But today is the day. So, this is going to be one of those episodes where we talk about an individual standard test method. And Russell is going to talk about the test a little bit and say some common nonconformities that he observes when he's performing assessments and then we will go over to Jon McCabe and talk about how a laboratory can correct those issues. So as part of the AASHTO Accreditation Program, all laboratories are required to resolve nonconformities within 60 days of the published report issuance. And that is kind of the context of which we are going to talk about this so. The test that we're going to talk about today is the plasticity index test, which is ASTM D4318 and AASHTO T 89 and AASHTO T 90. And this standard is used for soil classification and it also helps people determine how a soil is going to behave when moisture is added to it. Russ, before we go into the nonconformities, why don't you tell us just a summary of these test methods more than what I got. I gave a very general overview. If you give us a summary of the test methods and maybe some of the differences between AASHTO and ASTM versions, that would be great.
[00:02:30] Russell: Yeah, absolutely. The test will start with sample prep. So, all of the material has to be processed over a #40 sieve, you take the material, pass the number 46. And I think if you're doing the multipoint method and I'm generalizing here, you need a certain minimum sample mass somewhere in the 150 to 200 gram range. The AASHTO method, you can just add water to it and run the test immediately. The ASTM method requires you to let that sample sit 16 hours overnight before you run it, and that is important for some of your more clay materials that really need to temper. And then you separate 20 grams out for your plastic limit sample and your some people will run that first. Most people run it after they run the liquid limit, but then if you're running a multi-point method and there are two methods for determining the liquid limit, there's the multipoint. The one point. Don't let the one-point method fool you though. It's not just one point. And I think we're going to talk about that in a little bit. You're going to take your material and you're going to get it to about the consistency of peanut butter, a little smooth peanut butter.
[00:03:33] Russell: And if you put it in your liquid limit device, your first point should be somewhere between 25 and 35 blows. That's the goal that you're aiming for. So, you want 1 point 25 to 35, then you take a moisture content sample 1 sample, 20 to 30 blows, take a moisture content, and then another final at 15 to 25, take a moisture content sample. If you're running the AASHTO method, you need to make sure that. The difference between the maximum and minimum, are at least 10 blows. And then you're going to dry those samples back in the oven. Then you move on to the plastic limit sample, and I'm going to be honest, when I first saw this, I thought someone was playing a practical joke on me because all you really doing is taking your soil in 1 1/2 to 2 grand portions and rolling it out into worms. And you've reformed them and roll them into worms. Again. You get them down to about an eighth of an inch, and they should start to break apart. And when they do, you've pretty much got your plastic limit.
[00:04:27] Russell: You want at least 10 grams for AASHTO and one container or two grams of 6. Are two tins of 6 grams each for the ASTM, and you average those. Like I said, when I first saw that, I thought it was a joke. I'm like, I thought we were doing science. You guys were just playing with dirt. But you know, this really is one of the most important tests that we see. It's sort of the linchpin to identification of any kind of soil. And it's this has to be the most common test that we see in the field. So it's amazing to me that it's common as this test is that there are still a lot of findings that we write for this test method, as common as it is. And so, some of these things that we end up writing up can really drastically affect the quality of your results, you know. And these numbers really don't mean anything unless everybody's doing things exactly the same way. So. That's sort of why we do what we do and then what's so important about making sure that everybody's doing things the same way and that attention to detail that we. That we do during the assessment, that's why that's so important.
[00:05:35] Brian: And to your point about this test, if you're looking for a test that's going to be interesting to kids, to introduce them to soil science. I would say this is the test. It is very similar to playing with play dough. I mean, really anybody can do it. It's easy to figure out, like when you're done and how to get the result is pretty simple. They can calculate it too, because it's about as easy as it as it calculation as exists in any of the standards. So, a lot of a lot of good things about this test method in general for introducing people to soil science.
[00:06:21] Russell: It's accessible, but at the same time, the people that are the best at running this are the best because they do it a lot. If you're not all that familiar with the sample that you're running, this test can go pretty sideways pretty quickly. This is one of those test methods where if we're dealing with someone that has a lot of experience and they know the material that they're using this, the demonstration can take 15 minutes, 20 minutes. But if they're not experienced and they don't know the sample that they are running, this can take all day. So, I had too much water now there. That 10 blows and you've got to let it dry back to. And that could take all day. So, this is one of those where if you are going to be doing this during a laboratory assessment for us, please make sure that you know the material that you're running and make sure that it is plastic if. You're not going to get a pass if you say, oh my material doesn't have any plasticity to it. Sorry we can't run that. That doesn't work. You're going to have to find a new sample.
[00:07:15] Brian: So, let's get into it. We're not going to go based on strictly the numbers here for the, you know, most common nonconformities because sometimes those are really not the most interesting findings because if somebody gets a finding on some arcane part of the standard that maybe isn't that important. I don't want to focus too much time on that. So, let's talk about the ones that you've seen that people commonly misunderstand, Russ, what do you see out there?
[00:07:45] Russell: So, the first one I wanted to mention is checking the drop height. Now. People generally don't realize they have to do that every day. You can tell when you get to a lab if they do it every day because they've got a little piece of tape and they usually use the same tape for like a week at a time, and that tape is right there because you have to take a piece of tape and you put it on the bottom of the liquid limit cup, intersecting the point of ware and when you see people that are just used to doing that and then they've got their 10 millimeter gauge block sitting right there. You know, you you're confident that these are people that are checking that every day. But unfortunately, that's not the case. That's rarely the case most of the time. People just jump right into the test and then when you get toward the end, you have to say hey, so when was the last time you checked the drop height on that liquid limit device? And they always say last week, I think. And well, that's not good now. Those anybody who's had any experience with those limit devices knows that the screws that hold the liquid limit cup in place come loose pretty easily. It doesn't matter how hard you tighten those down; they're just going to come loose it. It's just what happens. And when they come loose.
[00:09:02] Russell: That's when you get a change in that drop height. Now that drop height is an 100% critical dimension when it comes to. How this test goes if you're running 12 millimeters drop height or 15 millimeters drop height, you're going to get a different value than someone who's running it at 10 or 8 or five. 10 is the number, 10 is what we expect to see. And you have to verify that, and we have to see it when we're there. If I say when was the last time you checked the drop and you say, oh, this morning before you got here? Well, I'm going to want to see it again. Going to want to see it again. So, I don't like writing this up because it's frustrating because of how important it is to make sure that that drop height is where it is most of the time. If people are good about checking it every day, it doesn't even need to be adjusted. They put the tape on there. They put the thing under there. When you turn the crank, you hear just a very light Ting sound. It's perfect, but it's perfect because they do it every day that they run. So. That's probably the most common.
[00:10:08] Brian: I agree with you. Uh, but what? Why is it so important?
[00:10:12] Russell: We're getting because that drop height is going to directly affect the number of blows it takes to close the sample in the cup, right? So, for those that are unfamiliar with the test, you're placing your wet soil in that cup, and then you're carving a groove out. And the depth of that material should be 10 millimeters. Now, if, as you turn the crank, that cup rises and drops and just to show you how important all of this is. There's even a resilience factor that the base of the cup has to be is it's going to get a different effect if you're dropping it on metal or wood or anything else. So, you know, if it's a all of this is controlled, and it's all controlled for a reason so that everybody's results are the same. So, as you turn the crank and it rises and it drops, eventually that soil starts to come back together. And when it forms in the center. I believe it's 1/4 inch across. Then you've got your number of blows and you know that's where you stop that point of the test. But if that height isn't the same if some of these, dropping it from a different height, they're going to get a different number of blows, and that's going to give you a different result for your test. That's why that part is so important. The drop height has to be the same kind of like the drop height on a on a Proctor hammer has to be the same every time. Right. We're measuring a total amount of energy with Proctor. And this case it's a height and a resilience that it has to bounce off of. So,
[00:11:43] Brian: That that's exactly what I was looking for. Is just kind of getting it in people's minds about why that repeatable height is important. So, Jon, as a Quality Analyst, when you see a nonconformity written about somebody not checking the drop height, what kind of response are you looking for corrective action, are you looking for?
[00:12:03] Jon: Typically, we just want to see a retraining record that shows, hey, you know, we went over this with the with the technician. Now they know what the start of each day, you know, to go ahead and check the drop height. Another really good thing. I think you know a lot of times too. Like Labs will just put a note up next to the liquid limit device and says did you check the drop height today or you can even just make it you could put it onto your worksheets that the tech is using and make it a check mark that says was dropped by checked those are all great things retraining is great but. People do fall back into old habits, so a lot of times, so it's always good to put the extra check in place there on the worksheet or just a note on the wall.
[00:12:43] Russell: It's funny you mentioned that note on the wall. I feel like I can always tell when the lab's been written up for something like that in the past because I'll see that note on the wall a lot of times. It's for something like a sieve analysis. They'll have a table on the wall with all the different sieves and the overload numbers, and you know that they've been probably written up in the past for having an overloaded sieve, but I agree 100% with what you're saying. That note on the wall is always a good reminder to people, and I like to see that when I'm in a lab.
[00:13:13] Brian: Another thing I like is on that particular one is making sure that that verification tool is available to the technician and is out there, right like so if you've got a little 10-millimeter gauge block that you use like make sure that's accessible to the technician don't have that in the lab manager's office or in some special place. You want to make sure that the right tools are accessible. Easy to locate every time. So good tips there, Jon?
[00:13:45] Jon: What you can always use the bottom part of the grooving tool as well. That's 10 millimeters. That's at the very end of it. You know, if you don't have that gauge block or you don't like to keep those things out in a pinch, you can always use the back of the grooving tool.
[00:14:00] Brian: That's a good point, and let's talk about that because there's two different kinds of grooving tools, right? And some of them have that and some of them don't. And AASHTO and ASTM have different grooming tools. And some of them have it. And some of it don't. Russ, do you wanted to give us a little background on that particular topic?
[00:14:16] Russell: Yeah. So, the quick version is the AASHTO gives you the option of using two different grooving tools. There's the curved grooving tool I believe it's called the Casagrande tool. And then there's a flat grooving tool. And that's the one that ASTM specifies. But I you can use it for AASHTO as well. Now the Casagrande tool, the curve grooving tool. Does have that 10-millimeter part at the end, so it's a block at the bottom of that, so you can use that. However, not all flat grooving tools have the 10-millimeter raised part on the on the bottom of it. The metal ones, which are great, don't have the 10-millimeter raised portion on the bottom. So, we see those metal grooving tools in a lot of laboratories, and they're great because they do last longer. If you think about the grooving tool tip on a plastic grooving tool, it's going to go out a lot quicker, especially if you're doing a lot of these because as you're scraping the groove out of the soil, you're wearing down the point and that point is supposed to be a certain height, so it's going to go out pretty quickly. But it does have that 10-millimeter base part on the end that you can use to check your drop height so. Generally, the metal ones are used if their long term. Now the only trick there is that metal grooving tools also going to carve because it's made of steel, it's going to start carving a groove into your brass cup. Brass is a lot softer than steel. Eventually you're going to carve a groove into your into your liquid limit cup. So just something to keep in mind.
[00:15:48] Brian: That's a good point. And from a materials perspective, it is curious that the manufacturers have gone with the steel grooving tool instead of a brass grooving tool. It seems like that would make a little bit more sense to have the same kind of materials properties. There's probably some reason that that was done, but I just don't know what it is. Uh, OK, so let's talk about the grooming tool a little bit more. What kind of issues do you commonly see with the grooming tools?
[00:16:14] Russell: So, the main issue is with the plastic ones and calibration records. So, the problem with the plastic ones is if you're doing a lot, you're going to probably go through it in a couple of weeks, maybe, maybe even shorter than that. But there are R18 requirements that those grouping tools do need to be checked. They're critical dimensions have to be verified. Now the interval in R18 is one year, but most of the time, these growing tools aren't going to make it a year. So, it can be tempting to just put one in service and not check it and say, well, I'm sure it's fine, but they come from the manufacturer and they're plastic, so they're just stamped. They come from the manufacturer out of tolerance all the time, so if you're not checking those and not recording that, then you are taking a risk that you're putting into service at grooving tool. That's just not the right dimensions. And again, that will affect the results of your test.
[00:17:08] Brian: Let's say I have a bag of those plastic grooving tools. How many of those do I need to check? When do I check them?
[00:17:17] Russell: You need to check them before you put one in the service. What we see in a lot of labs is they'll check all of them. The reality is, I think it's probably fine to check five or six of them and then put them all into service, take all the ones that you're not going to use and put them somewhere where your technicians can't get ahold of them, because what you don't want is your technicians using grooving tools that haven't been checked. So, put those away somewhere else. Make sure that the grooving tools that you have in service have serial numbers written on them, because everything in service has to have a number, and that might be a good indicator is to whether something's suitable for use as if it has a number on it. It's OK for a technician to use. If it doesn't, it's probably not been checked, so don't use it. So, if you're technician. But if you check five or six, that's probably going to get you through. You know, at least a few months, I would imagine. And then you can revisit that if they start to go bad, but at least with those plastic ones, I would recommend checking the tip on those every couple of weeks, especially if you're using them a lot.
[00:18:19] Brian: Yeah, that, that's a good, no pun intended, tip for people is to check the tip condition because it will get spread out. Jon, I don't want you to fall asleep over there, so I'm going to throw this over to you. Let's say I'm a lab and I was written up 2 assessments in a row for this. What kind of what kind of corrective action process should I take, not just about what to tell you, but what do you think you would do if you're a lab manager in that situation?
[00:18:44] Jon: I would definitely change the interval in which you go ahead and check that piece of equipment. I mean, if you're doing, if you're doing liquid limits every single day and you're only checking that grooving tool once a year, it's going to be out every single time. That that's always the way that I usually tell labs. It's like R18 says once a year, but you're allowed to change it, though to be more frequently. I mean, if you're doing 10 to 15 of those a day with just one plastic grooving tool, you might want to check that grooving tool once a month. Possibly, and just to double check it and you can have your official record for it, but then maybe just, you know, you'll just keep your calipers around or keep your eye compared or around and just check it once a week. Once a month. You know, change the interval and your quality manual for your calibration, standardization, check interval list and just do it once a month once every three months might be appropriate for you, but it's just it's just a good double check just to make sure that you're doing it right and it doesn't take that long to just go ahead and check a flat grooving tool. That's not as demanding as checking us sieve or something like that.
[00:00:00] Russell: Just to kind of, reiterate what Jon is saying, because he's 100% right, but one of the other things that's always interesting when we get to a lab is. We'll check a grooving tool and it'll be out. And that means we're going to have to write a finding. And generally, you'll hear something to the effect of men. I just checked that last week. You know. How is that out? One of the reasons that they're out is we're checking them in two completely different ways. If you're just using regular dial calipers or digital calipers to try and check the tip of that grooving tool. You're going to struggle to get a good measurement, an accurate measurement. We're using a jeweler’s eyepiece that has a millimeter scale on it. Now these are probably cheaper than the calipers that you're using cost wise, and there are a lot the utility on them though is much greater for checking something like this. Just to not have that headache of having to respond to this all the time, you spend the $30-40 on the jeweler’s eyepiece so that you can check the and they're so easy to use. Just hold it up and look at the tip. That's the best way to check those. I recommend everybody do that. That's what we're using and that's what we're basing our findings on, is the reading we get from one of those, and it's not going to compare to the measurement you get with a set of calipers, so.
[00:21:09] Jon: And it doesn't have to be calibrated every year.
[00:21:11] Brian: That's a great point. And I think some people don't realize how important that tool is and how useful that is that you're typical testing lab because you can check your fine sieves to see if you've got issues with your openings. Like they're just typically just have to get checked for condition. But I mean, you can see if there's something going on really easily. If you've got a tear in a 200 screen, for example, on a sieve that eyepiece is really handy. And what you just mentioned. This is corrected so that is that should be in every laboratory managers toolbox, and I'd also say as far as avoiding issues with this as you really need to delegate the authority to the people who use the tool to tell you, or either to tell you when to replace it or to do the replacement on their own and teach them how to do that. So, if I'm running a lab and we do a lot of plasticity index testing. I'm going to teach my technician how to check that tip. I'm going to have them do it regularly, and I'm going to have them be in charge of replacing it and rechecking the new one and putting it into service and just giving, like, give me the paperwork or let me know when you did it so I can log that properly. But I want you to be able to do this so we can make sure we don't run into this issue because. Lab manager is very busy. They've got a million things they need to keep track of, and if you can delegate that authority to somebody who's using that tool every day, it might work out a little better. So, try to think about your organization a little bit when you're having issues and don't just look at the base issue that you're dealing with. Try to kind of broaden the scope of your thought process. OK, Russ, it's probably enough on the grooving tools there. What else do you want to talk about?
[00:23:02] Russell: The other major finding that we write for the multi point method is not grabbing your moisture contents in the correct order. So again, your first point needs to be between 25 and 35 blows. A lot of times what happens is people are adding a little bit of moisture to their sample. They're mixing it and when they think they've got it in the right spot, they'll put it in their cup, they'll run the test and you know, maybe the first time they do it, they get like 45 or 50 blows or something. So, they had a little bit more water, remix it when they think they've got it, they put it back in the cup, they run the test, they run the point again. What should be happening is you're just adding a little bit of moisture at a time and working that down to that 25 to 35 below range. What happens all too often though, is someone just squirts a whole bunch of water on that sample, and you've just gone from 50 blows to like 12, and they'll get the sample in there. And maybe it's not 12. Maybe they get like a 15 or a 16 or something like that. And I'll just say, OK, well, I got my first point, and then they take that first point.
[00:24:10] Russell: Unfortunately, the method is very specific about the order that you take these, and you have to go dry to wet not wet to dry or not some other variation of that. So, if you get your first point at 15, do not take a moisture content sample, start drying your sample back, your first moisture content sample has to be between 25 and 35 blows. So again, we see all sorts of combinations of the order that people do that in. And this is this is when the test takes 3 1/2 hours to run and that's because you put way too much moisture on your sample. And now we've got to sit around and wait for it to dry. And one of the things you cannot do is just add more dry material to your already wet sample to try and dry it back that way That is specifically not allowed in the method, and I don't believe you can throw it in an oven either. You have to really just let it dry so. But it is extremely common and it is definitely spelled out very explicitly in the method. So.
[00:25:16] Brian: Now Jon, we're going to get into a lot of procedural findings here. So, what's your typical expectation as a quality analyst when you see a procedural finding written in a report? What's the corrective action, supporting documentation required?
[00:25:31] Jon: Just some sort of document that shows that technician had been retrained ever since the assessment happened, so don't just send in like an old training record from this current year. I will be looking for a record that has a date that shows that that the standard was gone over with the technician after the assessment date.
[00:25:47] Brian: OK, now what if there's a lot of them? What if it seems, and I know you've run into this before, what if you see so many nonconformities where you think that there's something else going on? Like is there? Is there a limit to how many nonconformities somebody that can have running a running a test?
[00:26:04] Jon: The assessor will judge that and would write a training failure note if something that really is bad. And then in that case, you know, we I might look at, OK, hey, you know, resubmit a new procedure that shows how you're training your employees to make sure it's an effective training method. Even just something, you know, just a new corrective action report showing what you're going to do differently this next time when you're training the technician because yeah, there's five or six notes for something like liquid limit, plastic limit. And they're all procedural notes. Yeah. We're going to want to dive a little bit more into how are you actually conducting the trade because something probably is not going right in that in that regards.
[00:26:40] Brian: Yeah, are ever times where you've asked for a video of the demonstration or will we made somebody get another assessment because there were so many issues.
[00:26:48] Jon: It happens a lot...not too much with the D4318 stuff. But if there's a bunch of notes, I mean, yeah, anything's possible if there is some failures in it, you know, we might go back and start looking at PSP scores as like, OK, hey, are you guys getting good scores here? But then you're doing very poorly on the assessment, so there's something's not right. So, we're probably going to start doing a deep dive into what's going on then.
[00:27:11] Brian: Thank you for that, Russ. Let's get back into it. What else do you want to talk about?
[00:27:15] Jon: Do you got a plastic limit one for us? Because otherwise it's going to turn into a liquid limit podcast.
[00:27:19] Brian: Oh, that's a good point. We haven't even touched on that.
[00:27:22] Russell: Yeah, we really haven't.
[00:27:23] Brian: It is rolling out little worms, right, [Russell: It is.] So, it's like not a whole lot can go wrong there.
[00:27:29] Russell: Well, you say that. You say that. I'm struggling to think of which mistake I see more during the plastic limit because there are there are a handful of very, very common mistakes that we see. I could kind of give you a brief overview of the more popular ones without getting too in-depth and into any single one, because I think people tend to make mistakes throughout this process and you're right, it seems simple because you're just rolling out worms. But there's a lot more to it than that. So, the first one being that they don't have enough starting material. Then the other one being that they're not rolling out the proper amount. You're supposed to roll out 1 1/2 to 2 gram portions, and sometimes people just take the entire 20 gram ball or 10 gram ball and try and roll the entire thing out at once. That's not what the methods asking for. They want you to roll that out in smaller samples. A lot of times if someone running the ASTM method, they're not getting 2 tins with six grams each in each tin.
[00:28:30] Russell: If you're running the AASHTO method, you're starting with a 10-gram sample and you have to do the entire 10 gram sample. However, you're not doing it all at once. You're doing it in smaller portions than 1 1/2 to 2 gram portions the other. The other issues that we see with this are a little bit weird. Sometimes people just have a hard time recognizing where that endpoint is, and where they should stop rolling the sample out. I've seen people roll these things out until they were practically dust and still trying to reform them and roll them out. But there's nothing to roll. It's just kind of a pile of dry dirt at that point. So, it's kind of interesting. We do see a lot of variation in this plastic limit test. The other piece of advice, I guess that I have for people. Don't use that plastic limit rolling device. It never works. I people love to break that thing out when we show up, but it almost always results in a finding. The reason is when you roll that it the soi l can't touch the sides of the plastic limit rolling device but with a 1 1/2 to 2 gram sample it will every single time touch the side of the plastic limit rolling device. So like it's nice because it it's got that predetermined 8th of an inch height built into it, but you're going to touch the sides every time. So just do it by hand. It's just so much easier.
[00:29:52] Brian: It's counterintuitive to use that. The point of that is you're trying to get it to dry and break, right. So, it's like using and this is probably another issue, the frosted glass on one side and then your fingers, which will also help facilitate the drying process. Those are really ideal for getting you to the endpoint of this test. Using that device is not ideal for getting to the end point and it's cumbersome.
[00:30:25] Russell: Yeah, I think it just makes the process more difficult. I don't know why it even exists. I don't see it solving any problem or making things easier. In fact, I think it just makes things more cumbersome because you're right, all you need to glass plate frosted side. You're right. Frosted side. All too often people use the non frosted side. But. Definitely use the frosted side.
[00:30:47] Brian: That in that screws people up too, because sometimes it will adhere if it's a little wet, it'll adhere to the unfrosted side and then they get a little frustrated and they're being watched so they get nervous and it's difficult. Like I feel for the lab techs when they go through the assessments. So, we talked about like we limit, we talked about plastic limit, what are there any other nonconformities that you wanted to highlight today?
[00:31:12] Russell: The only other one that I wanted to point out and it is not as common as I think some of these other findings that we talk about, but it is common if someone's going to run the one-point method. And that's not as popular a method as the multi- point method for liquid limit. But we do still see it. And generally, when somebody says I'm going to do the one-point method I know I'm about to write a finding. Because of how misunderstood this version of the test method is. People think that while I'm running one point, so I'm just going to run one point. I'm going to take the moisture content and it's going to be fine and that's just not how that works. The other thing is there's a big difference between how you do it for the AASHTO method and how you do it for the ASTM method. So, you need to be very specific with your assessor and they'll ask, but you need to be very specific, which one you're doing because they're so different.
[00:32:13] Russell: And I don't know how much detail you want me to get in on to get into on this one, but the essentials for this. Are instead of running three points, you're doing one point. It needs to be between 20 and 30 for ASTM or between 22 and 28 blows for AASHTO. So, once you've got one point in 22 to 28 blows for the AASHTO method, you immediately take all the material out of the cup, you return it to all of the other material that you have, remix it, not adding any water, just remixing. You immediately put it back in the cup, run the test again, and as long as you get that same between 22 and 28 blows, you can then take your water content specimen. However, if you're doing the ASTM method, you've got that 20 to 30 blow range. Once you get in that 20 to 30 blow range, you immediately take a moisture content sample. Then you take all that material, you put it back in the with the other material that was just off to the side. Remix it without adding any water.
[00:33:23] Russell: Put it back in and you have to get another point that's within two points of the point you just got. Then you had take another moisture content sample and you average those. So, it's a little bit more confusing. People think 1 point, oh I'll just do one point, but there's a whole lot more to it than just one point. And when we give people the option, sometimes we'll just say so you're going to do the multipoint or the one point and some people don't even know that there is a one-point method because the only thing they've ever done is. Multipoint and they go Oh well, I'm just going to do one point and that's not what we're talking about. We're talking about the actual method for doing it. So, when you say you're going to do that method, make sure you know what that is and make sure you know whether you're going to be doing the AASHTO or the ASTM because they are so different.
[00:34:10] Brian: I think that's really helpful, especially because it's kind of a misnomer calling it a one point. I mean I guess not necessarily because you are still taking one point at the end of the day as your result, but it takes 2 trials to come up with that one point. Yeah. Thank you for that detailed explanation and it really was what I was looking for, so. That the last thing I think we ought to talk about is the two things were related to moisture content you just touched on moisture content, but let's talk about what can happen in the process of performing these tests that people need to be aware of on moisture loss or retaining the moisture that you need for your test points.
[00:34:55] Russell: When we go about doing the moisture content. As soon as you've taken your moisture content sample for your liquid limit test as an example, if you don't immediately weigh it, you have to cover it. It's not a big sample, it's a small sample, and you're immediately losing moisture as it's just sitting out in the air. If you take a moisture content sample, put it in a tin and just let that tin sit there until you finish the test. The moisture content is going to be drastically different when you go to weigh that then it would have been when you started the test, when you actually took that sample. So, if you don't cover it, you need to immediately weigh it. If you're not going to immediately weigh your sample, you have to cover it. Now when it comes to plastic limit testing. Because you're doing a full 10 grams of material for AASHTO or two tins of 6 grams each, and you're rolling out 1 1/2 to 2 gram portions, you're never going to get that all in one shot. So as soon as you get. That one, that 1 1/2 to 2 gram sample down to the plastic limit point. You think you've got it at that right moisture content immediately put it in the tin and immediately cover it. There's no point there where you can just weigh it real quick and it's going to be fine because you need a total of 6 and you didn't get that. You're going to have to keep that covered. Until you get your 6 grams and until you weigh it, once you've got that initial weight, you can take the top off. It doesn't matter, it can lose moisture, it's going to lose it anyway. When you put it in the oven, but you've got to have it covered until you get the weight.
[00:36:27] Russell: One of the funnier things that we see is people putting it in the oven with the lid on. I'm not quite sure why people do that. It's kind of funny, but it's also kind of not funny. Where's that moisture going to go? So, make sure before you put those samples in the oven, you take the lids off so that they can dry properly.
[00:36:44] Jon: That's the finding that I see all the time and... Because you were hitting home so hard, you know, put the lid on, put the lid on, just make sure you take it off when you put it in the oven.
[00:36:55] Russell: That's always a head scratcher when I see it on a report. I'm like, really, it didn't take the lid off.
[00:37:00] Brian: That is probably like just nerves. When somebody does that, because it really doesn't make any sense
[00:37:07] Russell: You do have to monitor that. That's something you really want to be careful of because they lose moisture so quick. Keep them covered until they go in the oven until you weigh them.
[00:37:15] Brian: So, OK, let's talk about the use of this equipment. So eventually over time, we've talked about how it has a brass cup and that can get worn out. But what are the wares spots that people should watch out for to make sure that their equipment is still in spec over time?
[00:37:33] Russell: Sure. So, there are two wear spots. One is on the bottom of the liquid limit cup and then one is going to be on the base that, that that comes in contact with the liquid limit device base. So those are things that we look at, things that we that we check when we're there on site. And we're checking the overall width of that point of contact. I believe the point of contact can't be any larger than 10 millimeters for ASTM or 13 millimeters for AASHTO and that's both on the base and the cup. So those are both things that you're going to have to check. One of the things that I find funny is every once in a while, you can just run your finger over that point of contact and you can feel let's like, indented. That's an old base that's been used a lot. And the on the other side of the cup, it actually starts to make a little flat spot on the bottom of the cup, which isn't what you want. So, these are things that you need to monitor and need to check. One of the nice things about the base though that I don't know a lot of people I don't know if a lot of people are aware of this, you can actually sand that down off the point of contact is getting too big. You can mill the face of that down a little bit and then that point of contact is fresh again.
[00:38:53] Russell: There's a quite a bit of tolerance in the height of the base. You can take a decent bit of material out of that I think it's. Not less than 42.5 millimeters or not less than 48 millimeters. So as long as the base is larger than 48 millimeters, you could actually sand that down. If you don't want to buy a new liquid limit base plate, you can actually sand that down to get rid of that wear spot and then you know, you've got a perfectly good liquid limit base plate again. Again, you're going to want to check your drop height if you've just sanded that down, but you should be checking that every day anyway. And then the other thing is there's a resiliency tester so that that base has to have a I think it's between 77 and 90% resiliency and there's a a special tester. Thingamajiggy doodad that you can use to check it. And it's my favorite thing to check when I'm actually out in the field checking equipment.
[00:39:51] Russell: It's got a magnet in the base and a little steel sphere, and you pull the magnet and the steel sphere drops and it has to rebound between the two marks that represent 77 and 90%. As long as that happens, it's good. I've never actually seen one fail for that. But I like doing that test anyway. I usually run it a couple of times just because it's fun, even though ohh it always passes and. I think you can buy them commercially, but they're dimensions in the method. If you want to try and make one yourself.
[00:40:21] Brian: The test method is just fun as far as test methods go. Jon, what would you do if I'm a lab and I've got a base that's out of spec? What kind of advice would you give me? I'll order a new one. But I'm going to keep that other one and put it on the shelf in case I ever need it.
[00:40:38] Jon: I mean, I would just take it out of service, throw it away. Because technicians come and go, you're going to find a different technician. Maybe. And they're just going to see it up there on the shelf, and there's going to grab and start using it one day. It's best just to just to remove it completely from service and just get rid of it. Get it out of the lab. Or just put it in your desk drawer and write on it says do not use. You know, the just don't put something away, you know, and either just completely get rid of it. Or I mean, I mean, I mean, I mean, I mean if it's a piece of equipment like you know, like Russ was saying that you could just sand it down really quick and do it, but you just don't feel like doing it, rather just get a new one. And that's a different story. But you should probably still put it big out of service tag on it somewhere. So, people know like, hey, we can't use this until we do XY and Z to it.
[00:41:29] Brian: Yeah, that's one thing I wish that I could go back in time and find out when the example in R 18 was put in that said that you can just tag the equipment out of service instead of discarding it, because I think that that led to a lot of people having that procedure, which led to a lot of people keeping out of spec equipment around which usually gravitates back into service without unintentionally getting back into service. So that can be dangerous. Yeah. And there's one other issue, just so we don't forget that I know gets written up, but it's kind of an observation where when someone's running the liquid limit test, they've got their material out. And to preserve the moisture, you're supposed to put some kind of cover on it. And we talked before we started recording about how none of us are really sold on that being that critical, but it is in the standard to retain that moisture. So that's something you have to do. So, they will get written up. If they don't do it. But we don't really make a big deal out of it.
[00:42:30] Russell: Yeah. And you can cover it however you want. I've seen lots of different versions of how people do that. Some people have Ziploc bags, they put the whole container full of soil in and zip it up while they're doing their number of blows. I've some seen people just take a mildly wet cloth, stick it over the top of that. That works too. Whatever you're going to do, just make sure you've got that sample covered. We don't like writing that finding. It's not something we enjoy doing but and. And what's even worse is when it's a. Repeat finding. That means it's now a nonconformity. Now you have to respond to that. I mean, you always have to do a correct faction, but now you have to submit that to your QA so you don't want to have to be put in that situation. One of the things I always tell every lab. Before I leave, when I when I'm going over there. Preliminary report is before your next assessment. Pull up your old report. Review it. You're going to have findings in your next report. It's going to happen, right? Because that's just the nature of this industry. And that's the nature of what we do. They're going to be findings. Go over that old report and make sure you're not making the same mistakes over and over again. Findings are findings, but repeat findings are more difficult to resolve, and you're going to want to avoid those. So, when I see somebody not cover the dish and they get that as a repeat finding, I know that they didn't pull up that old report, they didn't review it to make sure that they weren't making those same mistakes again.
[00:44:02] Brian: That’s really good general assessment advice for anybody. So, Jon, let me go over to you what kind of general advice would you give to somebody who is in the process of submitting corrective actions?
[00:44:12] Jon: Just if if it's a procedural note, do the retraining 99% of the time. If you have a procedural note most of the time it could be taken care of by submitting a training record if you haven't. If it's any equipment note, make sure you check the piece of equipment send in the send in the record, then to us so we can see that it's been checked. You know again you know we were talking about the frost glass not using that. Send a picture in showing that hey, we do have the proper equipment and then we retrain the technician to use it. People always think they have to spend all day on a corrective action. You really don't. It's really just retraining, submitting the documentation to us, showing that or, you know, submitting the new equipment check.
[00:44:56] Brian: I was going to ask you that too. When is it important to get a record from someone as part of their supporting evidence? What kind of nonconformities would trigger that as being part of the required corrective action and supporting documentation submittal?
[00:45:11] Jon: Any single time that there's an equipment that's out. So, at grooving tool that's out the brass cup might be out, you know anything with the liquid limit device I might want to see either a picture a packing slip you know showing that you know if it's a grooving tool. Ohh yeah. Hey so this one was out we took it out of service, and we brought a new one in or we ordered new liquid limit device submit me a picture or submit me a packing slip and then the check record to go along with it as far as training records we don't necessarily like require to submit training records. And but I am going to start taking a look at that though. You know, if there is multiple notes for the same test standard, if there is, if it's a repeat note, we're going to want to see a corrective action report along with the train record. So stuff like that.
[00:45:56] Russell: I actually have a question for you guys. Maybe you can answer for me. And because I've been asked this question in labs before and I've never really known the answer when it comes to a check record or verification record, whatever you want to call it for grooving tool. There are a lot of dimensions for that grooving tool in the method. How many of those dimensions are you are looking for on the record? Some of them are really kind of tricky to measure, especially if you're using the wrong tool. But you know how many of those dimensions are you guys looking for? All of them or some of them? People have asked me. I haven't known what to tell them. Just said check with your quality analyst.
[00:46:36] Jon: I mean typically for me, I'm looking at the width of the grooving tool, and that's really probably that. That's the main thing. I'm always looking at is. That's the one thing that's going to go out. I mean, I don't think measuring, you know, like the entire length of the grooving tool. Like, there's no, I mean, it doesn't really matter because you're not using that for anything. But I mean, my main thing is, is that I'm looking for the actual tip of that grooving tool.
[00:46:59] Brian: The width of the tip, the height of the projection that goes down and the width of the that it's like a... If you're looking at the ASTM one, that length of that flange it, that's a. That's a good one as well because that kind of gives you an idea of what the what that PAT is that you're working with, because it really shouldn't dig into it. [Russell: Mm-hmm.] Much when you're making that groove, so that's another one. But I think that most of it focuses around the tip of the grooving tool. And then we also want to make sure that whatever you're using for your height gauge. Whether it's the if, it's the end of the grooming tool that should be on that record as well. But if you have a separate gauge block that you use, I wouldn't expect to see that on the grooving tool record. But you're. I can see why that question comes up, because if you look at the standard, there are all kinds of dimensions because it's basically like if I'm going to build one of these devices, what do I need to know? So, like, I'm looking at this table of the Cam radius and Cam angle degrees. [Russell: Right.]
[00:48:04] Brian: And that is not something a laboratory is going to check. Nor should they even be worried about it. There's some things that you should just have the confidence that I bought this thing. And it is what it says it is and it resembles this. But there's a couple things like you mentioned, the resiliency of the of the base. There's actually an appendix or an annex in the standard that goes on to explain how to check that they're actually like if you look at the ASTM standard D4318, there's some pretty good information in there. Yeah. And it is an annex, so that's required. But there are good pictures to show you what the soil should look like in the cup. When you form the path that gets tested and when it is closed to the to the point at which you take that moisture content. So, I feel like this standard has been updated to the point where there's enough information for somebody to really know what they're doing, if they if they read this at least far as running the test is concerned, which is what we're talking about today. So, check that out. When this episode goes live, Kim will add some references to other either newsletter, articles, webinars, or other documents we have that could be helpful to people. And Russell, thank you so much for your time and expertise [Russell: Absolutely.] on this conversation. And Jon, I appreciate your time as well. Thank you so much.
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