EP #163: How to Fix Air in Concrete

Seth (00:00)And welcome to another episode of the Concrete Logic Podcast. in the last episode, we had Jason Adams on and he challenged one of the concrete industry's biggest assumptions that exterior concrete does not need air entrainment on exterior concrete. So today we're gonna take this conversation a little bit further with a with a new guest. my guest today isI'll call him Baker's resident concrete materials expert, Dr. Bruno Fong Martinez. Bruno earned his PhD from the University of Texas at Austin with a focus on concrete durability. Before joining Baker, he worked as a concrete engineer at Kiwit, and today he helps Baker develop and review specifications, optimize concrete mixes, troubleshoot fuel problems, and evaluate durability and surface life.He is also active on ACI and ASTM technical committees, which means he gets to see both of what the standards say and what actually happens when the concrete shows up on the job site. Bruno believes unnecessary air entrainment be may be one of the biggest preventable causes of concrete problems and waste. So today we are asking, are we putting air in too much concrete? So Bruno's gonna help us with that today. But before we get started, like I always do.I'm going to share with you how you can support the podcast. And the first thing is if you enjoyed the show, please share it with a colleague or a coworker. the next thing you can do is if you go to the the website for the podcast podcast, too much coffee today, Bruno. con if you go to www dot concrete logic podcast dot com, there's a couple ways you can get a hold of me. The w the first way is there's a at theTop of the navigation bar there, there's an option that says ask Seth. If you click on that, email form pops up. And what I'm looking for are topic or guest suggestions. 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He's he's donated to the show. so I appreciate that, Zach. and then the next way is if you want to learn more.more about these topics in more of an academic way and possibly if you need professional development hours or or CEUs if you need any any of those as a professional engineer you need to check out concrete logicacademy dot com. check that out. That's another way to get your PDHs and your CEUs if you need them. Or if you just want to learn if you're a concrete contractor, you want to learn more about concreteconcrete suppliers as well. that's a a good way to to continue learning about concrete on your own. So with that, Bruno, let's get to the topic at hand. are we putting air in too much concrete? That's what we're going to talk about today. so do you want to get us started on that topic? It seems to be something you're passionate about.Bruno (03:34)Sure thing. Thanks Seth and thanks for having me again listen to your episodes before, so I've gotten some good insight out of them. and yeah, this is sort of a passion project for me, this f specific topic topic, because it's such a such a simple one, that I just kicking myself in the head of why we can't get this right as an industry because if you talk aboutyou know, improving the industry any sort of way, either performance or sustainability or anything, like this is such a low-hanging fruit of like if we can as an industry agree on agree on air entrainment, we can improve concrete across the board, reduce cement content, reduce rejected trucks, improve thermal performance, improve other properties, and we can seem to get it right. in my relatively short career I've had many, many fights withwith some very big clients that have made me put air in some concrete that most definitely did not need it and that led to a bunch of issues and again there there's the unfortunately a bit of misunderstanding on the technical side and then also misunderstanding at the at the the constructability project side of what it actually does to your concrete so yeah have lots to say about itSeth (04:43)Yeah. Well good.Let's well I don't think we I did a particular good job in the l episode with Jason. I think if we could so let's let's start with this. You're not saying remove air entrainment totally out of the picture, right? You're just you're saying there's just there's applications for it and there's applications that it's not good for. Is that correct?Bruno (05:07)Correct. And I've broadly dividing it into what I'm gonna call likeyou know the red light, green light red light, yellow light, green light. So for example, red light. All of Canada. I mean, no question. You know, you're gonna need air entrainment, it's very severe freeze tow environment, for sure. You're gonna need it. And if you're if you're a concrete producer in those regions, you're used to it. You know how to produce it. yellow light. Let's talk about some of the states that maybe have part of the northern part of the state maybe has freezing cycle.But the southern part of the state does not. Texas would be a good example. Northern Texas can get cold, southern Texas does not. Greenlight, Hawaii. The lowest recorded temperature in Hawaii is sixty degrees. So if you want to talk about free and they still they have there are thousands of cubic yards of concrete with air and tremendous in Hawaii. That's for a fact.Seth (05:51)Well. And they stillOkay.All right. Let's let's go back to the basics. I think you'd be good to explain this. Let's explain f first air entrainment versus versus entrapped air. And then also can we talk about the mechanics of air entrainment? Like what what is it what are we trying to achieve in the concrete and why is it how it protects the the concrete from freeze thaw? If you could go over that and thenWell, we can start picking apart the things that you don't like about it.Bruno (06:27)Sure, and I'll be generic 'cause I I didn't particularly prepare on the the mechanisms itself because air in freestyle protection is actually very complicated, so I'll I'll keep it pretty basic. in general just the mix the process of mixing concrete, whether it's a a l a lav mixer or a truck, and entraps air, just because you're blending materials, you know, you're just trapping air. That that blending process inherently traps air and we call thatentrapped and typically we give that a number of 0 to 3% by volume. So any concrete out there that you mix it in a ready mix truck is probably gonna have 2%. 2% is a good a good middle value. Those voids again just happened from the mixing action. Most of the voids got collapsed during the mixing but some remain. But they tend to be what I'm just gonna say like on the a little bit of a larger side of of bubbles.not enough to to help you with freezing and thawing.if you put an air and trainer chemical in your concrete, that this air intrainer, you can think of it sort of a little soap protector thing. So it protects your air bubbles as you're mixing, they're not collapsing. So it doesn't necessarily create the bubbles, it just protects them, coats them, so prevents them from collapsing. So when you're mixing, when you have your mixing action, those bubbles remain and they tend to be of a better distribution, smaller size.better distribution so they're distributed through the throughout the whole concrete matrix and that percentage tends to be maybe five or six percent which again you would not get from entrapped entrapped if you mix it properly you're gonna be in the two to three range with the chemical maybe you can get to a six seven and so on so that's basically I'll pause there if there's any comments from your endSeth (08:15)Yeah, that's perfect. The so when you do air entrainment, it it you protects the bubbles and there's and it kind of spreads the bubbles throughout the concrete so you don't have like entrapped air, wouldn't it be like, you know, you're supposed to get it out when you vibrate the concrete, right? That's why we're vibrating the call concrete to consolidate and get the air out of it. So when you have air entrainment that and you're actually putting anadmixture additive into the concrete to create that. The bubbles are supposed to go throughout the concrete evenly if it's done done right. Is that yeah.Bruno (08:51)Yeah, more orless. And again the the size of the bubbles is also different. I don't have it in front of me to tell you like the micron difference, but it's easy to tell when it's entrapped versus entrained because the entrained ones are are much smaller. So, you know, you the same amount of volume, like let's say one big bubble has a volume, but that volume can also be represented by let's say a hundred smaller bubbles dispersed. AndSeth (09:15)Mm-hmm.Bruno (09:16)it's better to have those hundred smaller bubbles all throughout than just one big bubble in the middle.Seth (09:21)Because I guess what I was getting at is we're the freeze thaw action of concrete is is when water gets in there and it freezes, it expands and then the the tiny bubbles kind of protect the concrete from giving it room to expand. Is that how that mechanism works? Is that why we are entering it?Bruno (09:39)Yes, that's theThe easier mechanism to explain, there's actually like s so there's no consensus really as to what mechanism exactly is taking place. you can read the literature and there's there's some some complicated ones that I I won't even try to to mention because I'm gonna I'm gonna mess them up. but the simplest one is based on that. It's there's water sat there's water saturated in the concrete, there's a freezing event, the the waterSeth (09:51)Okay.Bruno (10:08)inside of the concrete pores wants to expand as it's basically transforming into ice ice is takes up a larger volume than water so then that extra volume needs somewhere to go so the the air voids basically provide release from that expansionso that's a that's a that's one of the mechanisms. It's not the only one. There's there's a couple other ones. but in in in effect, again, we we as an industry have agreed that if you put air entrainment on your concrete, you're good. we kinda see it as a as a very binary issue. You you toss air entrainment and you're good. one of the one of my specialties is durability and service life like you meant like you mentioned.And right now we actually don't know what we mean by saying you're good. Like we as an industry we don't know if that really means you're good for a hundred years, because that's what some of the some of the projects are looking for. right now this date is of the industry is like, yes, put in air entrainment and you're good. And we kind of assume that it's good for a hundred years, but we really don't know.Seth (11:09)I gotcha. Yeah. that was yeah, that was perfect. That's what I was looking for as an explanation of why, you know, the the the my understanding is we put Aaron Trayman in for exterior concrete because it's it's exposed to free the freeze thaw you know temperatures out there and that's what we're tr mainly trying to protect the concrete for. I'm not familiar with the other ones. It sounds like I need to do some reading. okay.Bruno (11:32)I can I can send it to you, but that that's that's from mygrad school days. and i it's a bit shocking to me that even, you know, we'reSeth (11:36)Okay.Bruno (11:40)As advanced as we are, there's no specific consensus. and part of it is that we just figured out we've somebody figured out Aaron Trainman works and we just call it good. but there's a lot more more need for research. a big part of the damage happens from it's a it's a cyclical nature. So it just like the name says freeze thaw, you need both the freezing and the thawing. And I don't think that's very well understood, so I'll I'll just highlight it.myself I live in Denver, Colorado, and Denver, Colorado has rampant freestyle damage because Denver gets cold, it snows, but it also gets very sunny. So there's actually a lot more freestaw cycles in Denver than in super cold places like Alaska.Alaska freezes and it stays frozen. And guess what? The damage happens when it's cyclically freezing and thawing because you have that water going into the pores, freezing and and then thawing and freezing and thawing and freezing.Seth (12:33)Yeah. Huh. well I think you kinda hit on something that I believe you have you take issue with is the testing for error. so I think that's one of the the the items that you had for that you wanted to talk about, is that right?Bruno (12:48)Yeah, so specifically when talking about regions of the country where you most definitely do not have freezing and thawing concerns, I'll keep using Hawaii as an example.The moment that you ask for air entrainment in your concrete, you're exponentially complicating things for everybody across the board. First of all, now the concrete producer needs the chemical. So that means that they need a now a new tank with the chemical and they need to pipe into the to the plant or whatever. That's an expense, that's a complication. Now you put your chemical in your concrete. Hopefully they get the dosage right, but who knows? Now that that concrete needs to be tested for an air content, and that's gonnaTo be another acceptance criteria. So all of a sudden, you know, your specification says you have to hit the right slump, maybe the right unit weight, but now also you need your air. And air is very complicated. Air changes with time actively in a truck. the more mixing action you can actually continue to destroy the air bubbles. also as a concrete sets, it can also you know make make a difference. SoNow that you have air entrainment, you have another criteria for testing to pass. it's also another test that somebody physically has to do and it takes time. If anyone's ever run an air test, like it's not a super fun thing to do. and my main issue is that it leads to a lot of waste. again, I'm specifically talking about Hawaii right now, because all of a sudden you can reject a truck if it doesn't have the right air because it's not within spec.it never needed the air and now you're rejecting trucks left and right. that's wasted material, wasted concrete that now is just gonna go somewhere else and is not in your job and you know, that's thousands of pounds of cement. regardless of what type of cement it is or what regardless of how green the cement or the SEM is, it's all waste. and it happens all the time.Seth (14:35)Yeah.So when you say other the complications, you you covered the on the supplier side. What about on the contractor side?Bruno (14:41)on the contractor side, a big issue with it is strength.So, I mean, inherently you can just picture if you have something full of air voids, it's not going to be as strong as as if it was just solid, a solid chunk versus now you have let's say six or seven percent. so typically the rule of thumb is that every percent of air drops your your strengt your compressive strength by about five percent. so that complicates everything down the road. Let's say this is a mass, a mass concrete element, and now you're being asked to to put air entrainment in it.Now you're gonna need to put more cement in it to make up for the loss in strength. But because you're mass concrete, you really don't want the cement because you're trying to be on the on the cooler side and more cement is gonna mean a higher temperature. So it's kind of backfiring there. you might need more fly ash to counteract that effect. Now you have more fly ash. Now maybe that's pushing your strengths to later on, beyond 28 days maybe to fix 56 days.You also have the potential for the admixtures to have an incompatibility. I typically don't like to put too many chemicals in my concrete. I I say if you have more chemicals than than than fingers in your hand, that's an issue. be sometimes they don't get along, even when they're the same brand. So that's on the contractor side of low strengths, thermal issues, complications with the mix, complications with the chemicals.Seth (16:00)What about on the pumping concrete and and placing and finishing?Bruno (16:04)Yeah,good point. so like I said, air content is actively changing in fresh concrete. So the time that it leaves the the the plant, it could change by the time you get to the site and then it could change again by the time it gets pumped.Typically it's it's a rule of thumb that you lose maybe one percent across the pump. it can really vary based on the configuration, the length of the the pump, but typically you're you're expecting it to drop, which means that you're gonna ask the plant to just hike up the air way high to account for the transport time to account for the pumping, because sometimes the job will ask you to to do acceptance out of the pump.So again, you're just asking for so much complication when you didn't need it, right off the bat. So all of that, unnecessary problems, unnecessary rejected trucks, unnecessarily low brakes, more cement is is happening actively.Seth (16:59)So where so where is where would you say air is air entrainment is necessary? 'Cause you're w we're not you're not advocating a removing it at all. So where where is it necessary? You said Canada, you said it sounds like most of the United States and then southern part of the United States you're you're saying doesn't need it?Bruno (17:22)Correct. And I'll go back to again the the red light, green light, yellow light analogy. I think one of the keyresearch items that is missing is how to address the yellow the yellow zone. so I recently had a call with Professor Anton Schindler from Auburn University and he is doing he's part of a a research project with with the Alabama DOT where they're trying to figure out for their state, again, where is whatHow do you map the the state? How do you map? How do you create a map at a state level that takes into account freezing cycles, not only freezing cycles, but also saturation cycles? So it's both precipitation and freezing. And that's how you're able to tell, okay, where's my my high-risk zones? Where's my low risk zones? Where can I remove air entrainment? Where do I need to go to the severe zone? Where do I need to go to the moderate air? and just broadly, if you're severe, you just need more air content. If you're moderate, youneed less if you're if you're in the negligible zone then you just you're good with entrap there. so right now I would say like that's part of the issue is that weAgain, somebody discovered that air entrainment was good and we just took it as a blanket statement and said, put air in it. Who cares how much? Who cares how much is the appropriate? We know that it works, so just go with it. and we were kinda overshooting it in my opinion. because that level ofof dialing down in a in a geographical zone, you know, mapping the the the freezing cycles, the precipitation cycles, that has not happened, that work. and again I'm I'm collaborating with this profess or discussing with this professor at Auburn on on how they're doing it for Alabama specifically and maybe this is the beginning of a larger initiative for more states to adopt.so that's that's kinda where it's at.Seth (19:05)Okay. So it sounds like we got some work to do to figure out what that what that is. Is is I think we covered you d definitely where it's necessary. So how how do we approach this from job to job? Are you making any changes now with with our Baker projects are looking at this?Bruno (19:24)Yeah.So I'll say that it I I understand the root cause of this issue again is the in construction industry is, you know, very restrictive by design for a reason. We want safe structures. Nobody wants any collapses. and so it's very understandable that we've gone in this direction.But again, I think we we we've overcorrected. And also another part of the issue is that the way that designs are being done nowadays, you have giant design conglomerates that have offices all over the country, all over the world, and you have people from northern climates that are used to northern climates designing in Hawaii, West Texas, and without understanding what what that is. And they're used to putting errand trainment in their specs.They don't have any issue with that, so they just copy paste the spec from Canada into West Texas, from Michigan into Hawaii, whatever. All of that happens all the time. And understand where it comes from. you also havea severe lack of just education within the structural engineering community about concrete materials. I myself am a materials engineer. It would be a crime to call me a structural engineer. unfortunately I don't think structural structural engineers I don't think have that level of awareness that they don't know concrete. They know the structural side, they know the numbers, but they don't know the concrete side. They just think concrete's this menu that you check boxes and they say give me the air, give me the strength, give me the durability.bang bang bang bang and I think they're asking for too much and there's a limit to what the materials can do.so that's kind of where the issue is coming from. How I engage with it. I engage with a a a baker project. ideally I get the specs early on and I see that there is air entrainment. this there's a current project in Louisiana that this is going on and this is the best case scenario because we this was brought to my attention. I submitted an RFI requesting removal of air and the client accepted.And that very small step probably has saved, you know, innumerable pounds of cement and rejected trucks and whatever things. And it show it goes to show that people are throwing things into the specs without really knowing what they're asking for. They're just copy pasting the signs from somewhere else, from somebody else, and very few people are taking the initiative in and getting project specific specs for the specific environment.but yeah, that's again the best case scenario is we RFI it, client agrees, we see an optimization, let's do it. there's been other cases where the client does not agree and they stick to their guns and we we build in error entrainment to the the estimate and it gets placed. That also happens.Seth (22:00)Yeah. At least two, it gets documented that you know we questioned the the specification on having the errand trainment in there. So if there is an issue with the concrete down the line we could be like, we ha we did ask you about this.Bruno (22:14)We did.part of the issue, the broader issue is not all parties have a dedicated concrete subject matter expert like myself. And so if we're if I'm trying to initiate this discussion with a client or with a an engineer of recordif they don't know about errant treatment, they're just gonna they're gonna step back and just rely on what they've done. You know, they they don't know me. They don't know maybe they don't know Baker, they have no reason to believe me, they don't wanna, you know, go through the hassle of learning the the mechanisms and so they just rely on what they've done before and it's easy to say reject, no, follow the spec, do as told.Seth (22:52)Yeah.Bruno (22:53)so there's a little bit of I think everybody can d learn a little bit.Seth (22:56)Well now you can point to this podcast episode. Just s you can send it to say, Listen to this. It's only about twenty, twenty five minutes long and I'll explain to you what I'm trying to get at and there you go. ThenBruno (22:59)Yeah.I will say because this has become such a passion project for me, I have reached out to industry folks because again, if it's just coming from me, honestly people I mean there's not good reason to to listen to me. but I have reached out to industry folks, specifically at ACI to see if we can take a stronger stance against this because everyone in in the technical academic circles, I mean I think they agree with me, but the document the theThe industry documents are not they're not as black and white and say don't use air in Hawaii, but I think they should be. So one of the initiatives that I'm pursuing, in addition with with talking with Professor Schindler Auburn isCan we come out with a an ACI stamp document? Something like a a tech note, which is a very brief memo, a note, which just says, for this issue, we as an industry, this is ACI, the durability committee, this is what we recommend. So I'm hoping again, once that gets going, if that document does come to light,then I can say it's like it's not just my word, it's the group of ACI experts. We got together, we wrote this very short document saying, This is when you use air, this is when you don't use air, please follow it. This is an industry consensus. It's not just, you know, my own dream.Seth (24:25)Not Bruno's dream. ACI agrees with me. All right. Well, that's great. I think that's a good spot to end the day, Bruno. If if folks want to reach out to you, especially our I think we're around thirteen thousand coworkers out there, they're listening to this. How what's the best way to reach out to you?Bruno (24:40)yes, so I'm again happy to engage with Baker projects, help them out with any concrete issues. not only specifically air, but anything if you wish there was anything better with the concrete, I can help with that. I am on the the the Baker directory. Email is Fong Martinez B at Baker Construction. but yeah, my my contact info is out there on on Teams and on Outlook for for Baker guys and gals.Seth (25:02)Yeah, and ifyeah, and if there's any engineers or architects out there that want to learn more about that, I'll I'll put a link to Bruno his profile on the on the website on our show notes, I'm sorry, that will lead you to the website so you guys can get a hold of him and sounds like we can help you eliminate some cement if that's goal for you. So Bruno, I appreciate you coming on the show today. It was fun. I hope youcome back and we can question more things that we can help concrete out with.Bruno (25:31)Sure thing. Thank you, Seth, appreciate it.Seth (25:33)Yep. And folks, until next time, let's keep it concrete.