EP #111: How Do Standards and SCMs Shape Concrete Durability?

Seth Tandett (00:01.206)
Welcome to another episode of the Concrete Logic podcast. And today I have Larry Sutter with me. Larry Sutter's principal engineer for Sutter engineering, but you probably know him from his work at the Michigan Technological University and the numerous committees he sits on, ASTM, and he's sat on ACI committees as well. Today.

Larry is going to, share with us how we develop standards, and specifications for SEM. So, specifically, fly ash and slag. And we may talk about some other materials as well. And that's what we're going to start with. And if it, if it goes to somewhere else, it goes to somewhere else. We'll see. but, before we get started, I just want to make sure you all, remember how you can support the podcast.

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Seth Tandett (02:24.066)
ConcreteLogicAcademy.com. You can join several ways there. There's a network that you can join where we got folks in there that are, it's kind of like a mini LinkedIn. can do that. We also have courses that we're offering as well. So you can get professional development hours. But essentially what we're doing is we found a way to enhance the podcast experience by

adding quizzes to the end of the podcast. So you'll listen to the podcast and you can take a quiz and then we can give you a professional development hours. So check that out. and with that, Larry, I think that's all my selling for today. That's that's

Larry (03:09.284)
Well, hopefully I don't have to take the quiz to complete my role here.

Seth Tandett (03:15.142)
No, no quizzes for you today. we might have you do make the quiz since yeah there, since you've been a professor. They, I'm sure you've done that a little bit. Well, I I'm glad we connected, and, you, you, you agreed to come on the show. So there's, you're a lot of your work, has been with SCM's, fly ash and, and slag. And so I,

Larry (03:20.684)
there you go.

Larry (03:25.712)
I've that a couple times, yeah.

Seth Tandett (03:44.364)
Like I was saying, if you could share first how those standards for those two materials are developed. And maybe you were pointing out before we hit record that there's a difference between standards and specifications. So maybe we define that first and then we talk about how to develop the standards and specifications for each one of those.

Larry (04:09.456)
Yeah, so maybe just a brief background of how I ever stumbled into this world to begin with. My work previously had been in the area of concrete durability and anyone who has studied concrete durability in the literature or in their own experimentation has most likely learned that if you want to improve concrete durability, concrete already is a very durable

material. If you want to improve that durability, easiest way to do that is through the use of SCMs. The other thing that most people have probably discovered working with SCMs is variability in properties. You don't always get the same result necessarily. this whole

issue really drove me towards the area of testing and specifications of these materials. I got involved with ASTM, I don't know how long ago it was, probably 25 years ago.

And after the first couple of meetings, I started attending the SCM subcommittee meeting and really getting more involved in what they're talking about because it it resonated with me with regards to the other work that I'd already been doing in concrete durability that there was actually something here of value to be attained. There was improvements that could be made in the tests and in the specifications. And so I guess I saw an opportunity or a need, however you want to look at it.

to try to contribute in that area. So that's how I got there. So as we were talking at the beginning, and I'm guilty of this, I do it, but I try not to do it.

Larry (06:01.744)
The term standard gets tossed around very loosely. And right now we have a lot of people coming into our industry who are not necessarily concrete people who are looking to improve concrete, particularly the carbon footprint of concrete. And you hear this word used a lot. And they use standard specification interchangeably. A standard is simply a document that has been developed under a consensus process, a document that we all agree on. And consensus doesn't mean that it's the best.

it means it's the lowest common denominator. We've reached something we all can agree on. A standard could be a specification for a material, could be a test method, it could be a practice, could be a guide.

could be a lot of different things. But a standard basically is a document that we as an industry have all agreed upon. It's been developed in a consensus process where we've had representation from all aspects, all stakeholders, and we've reached an agreement on what that document should say, and we call it a standard. And ASTM is the principal developer, the source of standards in the US for the construction industry.

source of standards is AASHTO, American Association of State Highway Transportation Officials. Those standards are primarily used in transportation construction, but between those two they cover probably 95, if not more, of the national standards. There clearly are specifications and test methods developed locally at the DOT level or even at lower levels.

You can argue whether those are not standards. I think it depends on how they're developed. But a standard is generally accepted, is document that is accepted by anyone who's subscribing to it as being, know, the, we're in agreement that that is the document we're gonna work from. Specification is another term that gets misused a lot.

Larry (08:09.68)
It gets misunderstood. And I think probably my colleagues in academia are more guilty than anyone. That is thinking that a specification is going to be a textbook, or it's going to be a research paper, or it's going to be something that's going to provide some sort of source of enlightenment to the user and how to use that material.

And it's not, a specification is the basis of a contract between the buyer and the seller. A specification tells the buyer what to expect or how to measure that material, and the specification tells the producer what they have to do to produce that material. And later analyze the issue of variability. When we start talking about variability in...

materials and performance materials, the question always comes back to are we measuring the right things in our specifications? Are we measuring the right properties? And if we are...

measuring the right properties, are we setting limits or boundaries on those properties that are either, that are both attainable by the producer and make sense to the user from a standpoint of how the concrete's going to vary as that property varies.

So that's really the challenge of writing specifications is trying to understand that you're not, it's not a scientific paper, but at the same time you need to base what you're doing in science. You need to have test methods that are agreed upon, hence the standard test methods. Those test methods have to have known.

Larry (09:50.352)
precision and bias so we can understand what the variability is in the result. And we set limits on certain properties and we set limits on properties that matter and we don't set limits on properties that don't matter. We still may measure them because they might be of interest but we don't set a limit on things that don't matter. You can put all that in a bag and shake it up and dump it out on the table and that's the makings of specification.

Seth Tandett (10:17.016)
So can we talk a little bit about, I guess, the standards for, we could start with fly ash. I guess there's a previous podcast, we talk about class F fly ash. I guess that's the pretty, is the dominant material right now. Is that true?

Larry (10:44.656)
Fly ash is still the predominant material we're using as SCM in concrete. I assume your listeners know the term SCM, stands for Supplementary Seventitious Material, which means we use it as either a replacement or an addition to the cement component of the concrete, typically Portland cement, but not necessarily Portland cement.

Seth Tandett (10:49.176)
Mm-hmm.

Larry (11:07.728)
So fly ash is probably two thirds from the numbers I've seen recently, probably two thirds of the SEM use still in the United States is fly ash. Fly ash is a very interesting material. I believe it was 1937 that Davis published the seminal paper on fly ash use in concrete.

And if you go back and read that paper, pretty much anything you need to know about fly ash, they covered in that paper. I don't think there's been a lot new developed. I mean, there's been some new developed, obviously, but that paper was just amazing in how comprehensive it was. The first specification for fly ash, to my knowledge, was ASTM T350, which was published in 1954.

And there we look at those two documents, Davis's paper which is very scientific and in depth and rigorous. And you look at the specification, you start to see certainly the difference between what a specification and the scientific paper is, but also the role of a specification or the perceived role of specification in the industry. When T350 was written, fly ash was treated as sand.

it wasn't considered part of this human tissues material concrete and there's a lot of reasons why that probably was the case. Most of them are economic or market driven or not driven by science and conversely or so as a result you know the specification for fly ash evolved from that standpoint we're using it not as a cement replacement but as a sand replacement or as addition to sand.

Fly ash was inexpensive when it first came out, so although it was used as a sand replacement, people learned pretty quickly that we used it to replace cement. And before long, we stumbled over the fact that it could actually improve the durability of concrete. And that started us down the path nearly 100 years ago of fly ash use. And fly ash is abundant.

Larry (13:23.536)
It's been used, it's been, you know, coal fired power was our mainstay up until, you know, 10 years ago, well 15 years ago. And so it was always there, it was expensive, it worked, and it just grew and just took over the market. The standard currently C618, ASCM C618, actual M295 are the specifications for

fly ash and they still have elements in those documents that date back to 1954. You can still find verbiage, can still find tests, you can still find the limits that were set back when we didn't even really know how to use the material. Now we need to, now we know how to use the material. know it's a replacement for cement, we know the benefits of it and so the tests that we made are evolving.

Whereas before we were just mainly worried about fly ash doing no harm, we developed tests like the Strength Activity Index test, which is actually a fairly recent addition to the specification. It was added in the 1960s, believe, early 1970s. And we have, we used that for many years as a way of trying to measure strength contribution.

And what we know from research and from experience is that in many cases it doesn't tell us anything about strength contribution. And so you started by talking about class F ash in particular. Class F ash is a very slowly reacting material. And you get strength at a much later time period in the concrete life.

And so the strength activity index, we're measuring strength contribution of seven days. Basically, we're looking for it to do no harm in that test. And if we let that test run out longer, we can maybe see the contribution. But who wants to wait 28 or 56 days for a test result? Not too many people. So the whole issue of measuring the reactivity of the material has emerged. And new tests have been developed.

Larry (15:41.472)
ASTM has developed a new test method based on research that was done in Europe under the RYLM program. And those are referred to as the R3 tests for measuring the reactivity material. They measure the heat evolution from the reaction of the material or else they measure the amount of water bound in the chemical reaction with the material. It's called the bound water test.

And this is an emerging test now that's been standardized. It is a standard test. And now we're starting to inch it into our specifications, trying to figure out how to use it in our specifications. And there's many challenges to that. I number one is what are the limits and what do they mean? But number two is even if we can decide on what the limits are, what they mean, as a user, what do you do with it?

So might tell you that I have a bottle of water content of five grams, 400 grams of cementitious material. Already this production is going to go. So what do I do with that number? So it comes back to trial batching, beginning experience for the material, understanding how the material works, and then going back to your other point you made earlier, the consistency. And it comes back to the point of

If the number five works for me and I get the right, with my mix design I can get the performance I'm looking for, then how consistent is that number five? And what kind of variability is going to make a difference? Is a four going to be a problem? Can I go down to three? What kind of variability in that number, whatever that number is, can I tolerate? And what does it mean if it varies? That comes from experience on the user end.

And we can't necessarily look at our specifications to provide that answer. We have to rely to some extent on the user, to a great extent, on the user community to become familiar with these tests and these materials and understand how to use them. And as we evolve new specifications, this is the biggest challenge, trying to go away from something we've done for 100 years towards something new that is completely different.

Larry (17:58.638)
that we don't really necessarily have the experience with and try to figure out how to make concrete with it.

Seth Tandett (18:03.83)
Yeah. I just wanted to back up to your comment. How did they determine that including fly ash and concrete, it makes concrete more durable? How was that discovered?

Larry (18:19.536)
That was some other work that followed on from, well, I guess we need to kind of qualify that. The first thing that was discovered was that fly ash was a way to mitigate alkalized silicon reactivity. And Stanton was the person who published that. I believe Stanton worked for the California.

Department of Roads, believe it was at that time, now Caltrans. They had ASR issues with the bridges and through research he determined that adding fly ash would mitigate the ASR problem.

And that was really the first thing we realized. And so I kind of made an offhand comment about Davis's paper pretty much told us everything, and to a very extent it did. But what we have really spent a lot of time on since then is understanding the mechanisms of how does fly ash improve durability, and how does fly ash mitigate ASR. And what we've learned is that...

There's some chemical reactions that help mitigate ASR specifically, but there's some general reactions where the fly ash or the SEM, I don't want to just focus on fly ash, SEMs in general, reduce the permeability of the concrete.

And back to my professor days, I always tell students that any bad thing that happens to concrete involves water. So if you can keep the water out of concrete, you can go a long way towards improving the durability. And that's what SCMs do for us is they reduce the permeability of

Larry (20:03.884)
so water cannot ingress. And that just pretty much shuts down every bad thing that can happen, whether it's a sulfate attack, whether it's the ice-hurt attack, whether it's ASR, removing that water is a big thing. And understanding the permeability impacts of SCMs and permeability is that, in my opinion, it's at the heart of really understanding how SCMs contribute. And that's another area where tests are being developed, research is being done.

methodologies for measuring bulk resistivity, other things of that nature, to try to assess the impact of SCMs and permeability.

That's really the key thing I think we've learned beyond what Stanton told us and he touched on probability in his work. But the past 50 years we've really come to a much better understanding of how that happens and why that happens and how to use materials to achieve that.

Seth Tandett (21:06.658)
So using fly ash, it allows the water that's in the mix to disperse, I guess, more efficiently. Is that what I'm hearing?

Larry (21:20.304)
So cement, cement when it hydrates forms a porous structure. And hardened cement is really a mixture of two things, calcium silicate hydrate and calcium hydroxide. And the calcium hydroxide is soluble in water. And so the net result is you have a porous structure and you have one component of it that's soluble. And so water can infiltrate to begin with.

Seth Tandett (21:26.379)
Okay.

Larry (21:48.31)
depending on the conditions that calcium hydroxide may dissolve. And so what we'd really like to do is plug up that pore structure. What pozzolins do, like a class of fly ash or a silica fume, is they chemically react with that calcium hydroxide and form more calcium silicate hydrate or CSH, and it plugs up the holes.

And that's so that's really what happens in any SCM is that you get a chemical reaction that produces more CSH, reduces the pores between the CSH in the cement matrix, and decreases the water ingress or any sort of fluid ingress into the concrete. So it's really a matter of producing more of good stuff and heating up some of bad stuff.

Seth Tandett (22:43.01)
OK. I understand that. So the new test method that you mentioned, it was called R3, is that right?

Larry (22:52.484)
The actual test method is ASCMC 1897 and it has a much longer title. I'd have to pull it up to recite it to you. But it basically is isothermal measurement reactivity based on isothermal calorimetry and bottled water measurements. And I don't have the exact title right.

It's of that nature. The R3 is kind of a term that was coined by the Rylem people. Rylem is a research organization in Europe, and they coined the term R3 as rapid, reliable, and reproducible.

Seth Tandett (23:15.352)
Okay.

Larry (23:30.544)
And so in their publication they started calling it the R3 test and that has caught on in the vernacular. You hear a lot of people talk about the R3 test. They're talking about ASTMC 1897, a standard test method.

Seth Tandett (23:45.044)
OK. And was that test method used on other material? did it?

Larry (23:50.864)
It's been used primarily for, well it's been used only for evaluating SCMs, but a wide range of SCMs. Fly ash, slags, natural pozzolans, calcine clay, silica fume, and some other industrial byproducts. There was an extensive body of literature out there on using these tests in a variety of materials. The majority of the work has been done with fly ash, calcine clay, natural pozzolans, and slags.

Seth Tandett (24:22.392)
So they found the ideal fly ash.

Larry (24:27.716)
But, again, the test method just tells you the property, it tells you the reactivity of the material. So if you put it in the presence of a calcium hydroxide solution, going back to this idea that SCMs react with calcium hydroxide, you put this material in presence of a calcium hydroxide solution, it's going to react. And we measure the extent of that chemical reaction. And we measure that extent by measuring the heat that's given off by the chemical reaction.

or by measuring the amount of water that is bound. So this calcium silicate hydrate I mentioned is calcium, silicon, and water combined to make a mineral. And so if you're going to take calcium and silicon and water.

and make a mineral from a solution, the water is going to disappear. The water is going to get bound up in solids. And that's what we measure when we measure the volume of water. How much water from the solution that you put into the test was consumed making a new solid.

Seth Tandett (25:30.584)
I was just curious if it was a test that you know was used on another material and someone's like we can use it on fly ash as well or if they they were like okay this this fly ash we're really happy with this is the standard and this is how it reacts in this test so that's the that's the that standard that we're setting for all fly ash has to do like this ideal fly ash

Larry (26:00.302)
Yeah, that would be really wonderful if we could do that. mean, there is no such thing as an ideal fly ash. There is no such thing as an ideal Portland cement. All these materials, this is what we live with every day, is that every material we work with, including the rock for them, I don't have say accept the rock, but really including every material we work with for making concrete varies.

We don't have a luxury of a steel industry where they can make the material out to the second decimal place. It's always going to be the same, or plastics for that matter. Our material varies, it varies day to day, it varies job to job, it varies by location. And we have to live with that.

We can't ever, that's not gonna go away. It will never change. We have to learn how to live with it. So the question here is how do I measure what it is? So that's what the test tells us. And what is the reactivity? It gives us a number. As I said earlier, it might tell you you have five grams of bottled water.

Let's say you have 160 joules of heat evolution per gram of this material. So that's a number we can measure the quality of the material by.

What that number means is a whole different story. We have to start then correlating our experience with measuring that number and getting that number with making concrete and how the concrete performs. And generally speaking, as the reactivity increases, meaning we get more bound water or we get more heat evolution, as that increases, you're gonna get more strength development per pound of material. You're gonna get more development of

Larry (27:44.866)
other phases that are going to fill those voids and reduce the permeability. So generally speaking, as the number increases, the performance of the material is going to get better. And I want to emphasize generally speaking, because there's many many many caveats, we can spend three more podcasts talking about the caveats on that statement, but generally speaking that's true. A higher number is better.

The question then becomes, okay, fine, I got a higher number. And in many markets, you don't have a choice. It's not like you got 15 fly issues to pick from and you're gonna go pick the one with the highest number. You're gonna take the one you have available to you at the right price. The question is then, how is that number going to vary? Once I've developed my mix design and I have a certain level of reactivity in that material.

how is that number going to vary, and then what does that variance mean on my performance of my concrete? That comes from experience with the mixed design and making the concrete, testing the concrete, making the measurement, understanding the variability of the measurement, making the concrete, and looking at the effect of the variability on the concrete.

That's the step. And frankly, that's the step that we should have been doing with a fly ash 50 years ago. We never did it. We just said, give me a class F, give me a class C, put it in there and see what's going to work. And we had problems because it varied. Not all class F ash is the same as the other one. No class C ash is the same as another class C. They are not interchangeable parts. So we can't. And we just always went down the road of assuming they were interchangeable.

Seth Tandett (29:14.285)
Mm-hmm.

Larry (29:29.698)
changeable parts. I can just drop in any ash and life was going to be good. And we have problems. And we historically have had problems with variability. Everyone talks about variability in these materials. Well, as I said earlier, news flash, these materials are going to vary until the day we all die. And it's not going go away.

we have to learn how to live with that variability, measure that variability, and predict what the result of that variability is going to be on my concrete performance. And that's on us as concrete engineers using the material to understand how to work with that material and what the variability of that material means. And the best thing we can do as an industry is try to get the best tests we can to measure that variability. And that's where we're really trying to work on the ASTM, getting the best tests to measure that variability.

the starting point. So, you gotta make concrete to see what happens.

Seth Tandett (30:20.888)
So it's more to verify what you have so you know what to do within the mix design to work with what you have. It's not, hey this is good, this is good flash. No it's, okay, I understand.

Larry (30:26.606)
Right. There's no good or bad. It's what it is and then how is it varying. And those are the two key things that we want.

Seth Tandett (30:42.924)
So I guess my next question, it may be, I can already hear the answer, it varies. So the use of fly ash or any SEM is to offset the amount of cement that you're using. And there's various reasons to do that. When at one point in my career, it was to use it to reduce the cost of concrete and that's no longer the fact.

to reduce what we're calling the carbon footprint. So, and improve the debris. Okay, so that leads me to my next question. At what point are you putting too much SEM in your mix?

Larry (31:17.469)
and improve the durability.

Larry (31:29.616)
when you no longer improve the durability I guess or it becomes cost-ineffective. mean there's obviously we all know there's other things that affect concrete or other things we're concerned about with concrete I should say such as workability, placeability, strength development, how rapid am I gonna get my need to strength.

many other properties. So for example, you go to a very high replacement of a material like a class F ash for example, in a mix and long term it may be more durable and from a carbon footprint perspective, it's probably a step forward, it would be a step forward.

But if all of a sudden your schedule now is going to be increased because you can't move the forms because you're not gaining strength, there's an economic hit on the contractor or the owner or both. And you've got to live with that. So you're going to say, I can't live with that. I can't live with that impact on my schedule. So I'm going to back off on the fly ash. I'm going to use less. I'm going to get my strength quicker.

It's a trade-off of many, many, many variables. There isn't necessarily a right or wrong answer. You've to look at all the various variables that are out there and try to come to a conclusion on what is the best answer.

Seth Tandett (32:56.546)
Yeah. That was...

Larry (32:58.244)
This is probably a role for that infamous artificial intelligence. And it is being looked at for this purpose, because it is a multifaceted issue.

Seth Tandett (33:03.544)
you

huh.

Seth Tandett (33:13.74)
Yeah.

Like you said, it depends. It varies on where you're at and your mix design and everything.

Larry (33:26.16)
I I'm a big fan of SEMs. I've seen all the benefits. I've seen the downside too, but I've seen the benefits. so, my first instinct would be to answer your question by saying as much as possible. And I think I'd probably stick with that answer, but to find what I mean, which I just tried to do by saying as much as possible. I mean, if you start increasing the SEM content to the point where you start sacrificing other aspects of the material,

to start asking yourself is that worthwhile.

Seth Tandett (33:59.448)
Do you agree with specifications that put a cap on your SEM use? No. OK. Because I've seen them cap it at 40 or 50%.

Larry (34:04.59)
No. No.

Larry (34:10.254)
Yeah, but that wouldn't be so bad. I've seen caps of like 15 percent and 40 or 50 you probably can live with. no, mean that's another aspect of it. As we move forward towards low carbon concrete, we have to get out of this mindset that we're going to limit things because, you know, the materials that are available, all the other aspects of the job have to be considered. Many times there's things we can do that

Seth Tandett (34:15.095)
Right.

Larry (34:40.624)
that we can't get there because of the limits that are put on us in the specifications. Minimal submit contents, for example, and then like you say, maximum SEM contents. You just restrict the ready-mix producer or the concrete producer in terms of what they can actually do.

In cases, the limits are not a hindrance, but in many cases, the limits are a hindrance. It just ties their hands and limits how many options they have to try to achieve the other aspects of the project, which may be carbon reduction, may be rapid construction, or a number of different things.

Seth Tandett (35:23.064)
Yeah. So you're, if I was to guess you're a fan of performance specifications versus prescriptive. We had, we had Colin Lobo on the podcast recently. We did a whole podcast on performance versus prescriptive.

Larry (35:36.944)
Yeah, I think everyone is in favor of performance-based specifications until you get to the point of trying to define what performance means. Then all of sudden you have an issue of maybe a lack of a medium of science in some cases. So measuring performance, where do you measure it, how do you measure it, what is it, you know, all things have to be defined. I mean, without a doubt, performance specifications are the way to go.

And it's something, again, you hear a lot of people who are coming to our industry trying to achieve carbon reduction who don't know our industry. They start throwing this out as if it's a very simple solution, and it's far from a simple solution. It's something that's been talked about for as long as I've been in the industry. And it's not easy to achieve because we don't know what it is, how to measure it, where to measure it. And so there's many, many aspects to it.

Anything we can do to move towards measuring performance and move away from prescription, in my opinion, is a good thing if we can achieve it. question is, what is it how do do it?

Seth Tandett (36:41.752)
Yeah. In your work with SCMs and the effort of carbon neutrality, has anyone raised a question about the carbon footprint of producing a fly ash or a slag during its production?

Larry (36:59.664)
Yes, and again that's a whole another podcast. So we're in this world now living with EPDs, Environmental Product Declarations for materials. The Environmental Product Declaration for any given material is based upon a product category, OPCR.

And that product category rule draws the boundaries around where we measure energy and other inputs and where we don't measure those. And you can argue over what the PCR is or isn't, but the PCRs are defined for SCMs. And that's how we measure the energy input.

Yeah, it's a very controversial issue. think there are some particular on the power production side of the business who would like to see maybe more of the environmental impact of coal combustion assigned to the fly ash and not to the production of power. Whereas, loads of us on the concrete side are using this material.

say well it's a waste material, if we weren't here helping you take it away, not only would you, you know, well you wouldn't have any option, it'd just be increasing your carbon footprint because you'd be wasting this material, so we're doing you a favor. And that's euphemistically saying it, but the point is drawing that boundary is never simple and it's something that I...

Hopefully won't ever be involved with I just live with it someone else defines it and I'm not gonna throw any stones at it The PCRs and EPDs are what they are. There's people who spend their life understanding how to do this and what's right what's wrong and I'm just gonna use them and make concrete

Seth Tandett (38:41.336)
you

Seth Tandett (39:00.152)
All right. Well, I appreciate you using the term energy use versus the carbon footprint. I can get on board with that versus the other.

Larry (39:10.754)
Yeah, well that's where the carbon footprint comes from obviously, it's from the energy use.

Seth Tandett (39:16.354)
Well, it's obvious to folks like you, but I don't think it's obvious to everyone out there. Well, this was, this was great, Larry. I appreciate it. I think we covered a lot today and, if you, hopefully you liked doing this and we'll bring you back on. could talk about those other things that you said you can make three podcasts out of. I'll keep you that.

Larry (39:20.258)
No, that's probably true.

Larry (39:37.188)
Yeah

Well, yeah, there's a lot of depth to this.

I'll just say I have one other thing, and while we're talking about specifications, is ASTM, we are developing what we're referring to as a performance-based specification for SCMs. it's really, the intent of this was really to deal with the emerging materials. We've talked pretty much exclusively about fly ash, and we've hinted at slags and other materials, natural poslots, and they're there, and they're very important. And their uses of study are increasing.

Seth Tandett (39:43.691)
Yeah.

Seth Tandett (39:47.638)
Sure.

Larry (40:13.272)
But there's also a of emerging materials coming out.

If we go back historically, can do what we did, which is define a spec for fly ash, define a spec for slag, define a spec for a silica fume, and then end up with a book full of specifications. Or we can just take a step back and say what you said earlier is performance. What we really want to know in the end is how is this material going to perform? We want to measure key factors such as reactivity, and we want to understand the variability in those. So that's really kind of the philosophy behind

behind this specification we're developing for SCM's is to measure the key things, limit a few of them, and report the rest, and give the concrete producer the information they need to start engineering concrete by using these new materials. It's going to be a paradigm change, and everyone

but we have to take the first step somewhere. We are very close to having that specification done. When it is done, in theory that one specification could be used to specify any SEM.

In practice, it's going to be used for the emerging materials. Maybe with time, the existing materials like fly ash and slag and so on will migrate to that same specification. But we're trying to move down that road of measuring performance and reporting it and giving the concrete producer information to make informed decisions on how they design the material.

Larry (41:51.469)
So that standard is under development and hopefully within the next six months it's going to be developed and approved and moved towards publication.

Seth Tandett (42:04.984)
Cool. Well, we'll look forward to that and it'll be something else for us to discuss on the, on the podcast. if folks want to reach out to you, Larry, what's the best way? What's your preferred way?

Larry (42:21.312)
Email is the easiest. Sutter.engineering at gmail.com.

Seth Tandett (42:27.722)
Okay, all right, I'll put that in the show notes so folks can reach out to Larry. Larry, thank you for coming on the show today. I appreciate it. And folks, until next time, let's keep it concrete.