EP #133: Concrete, Climate, and the Missing Science of Evaporation

Seth Tandett (00:00)And welcome to another episode of the Concrete Logic Podcast. And today have Concrete Bob Higgins with me. And we're going to talk about, well, you know, for once I'm kind of playing in the head here. This is going to be episode 133. We're going to call it Concrete Climate and the Missing Science of Evaporation. Bob sent me an interesting email, as he always does, andabout this MIT, what do call those, papers?Bob Higgins (00:29)Yes, yes, study in an article.Seth Tandett (00:31)study.So don't stop listening yet. This is going to be good. I know this previous episode I did a solo episode about another paper about our favorite subject PLC or type 1l cement. This one's going to be great. This episode we're going to talk about a paper that MIT researchers discovered thatEvaporation is not necessarily caused by heat. They believe it's caused by, it can be light driven. So Bob's joining us today and we're going to talk about how, or what is in this paper and how that relates to concrete and the implications of such a study. Does that sound good, Bob? All right. Here we go.Bob Higgins (01:16)Sounds great.Seth Tandett (01:18)It's like we've done this before. All right. So I'm going to share my screen for folks watching on YouTube. If you're listening to the episode, we will explain what we're talking about. You're not missing out on it a whole lot. We're just looking at a very basic PowerPoint here.Bob Higgins (01:20)YouSeth Tandett (01:38)⁓ so why this episode again, I shared with you, Bob sent me an email, had this, ⁓ this paper in it. ⁓ these MIT researchers discovered a light driven evaporation. ⁓ this paper was accepted back in 2024. ⁓ the article suggests that, ⁓ that, you know, larger implications, ⁓ you know, beyond concrete thiswill have impacts on the climate models that we use for ⁓ climate change. ⁓ And then like I said, Bob's going to connect this to the concrete and maybe we'll talk about some curing too.Bob, you want to go ahead and talk about this MIT discovery?Bob Higgins (02:21)Yeah, when I came across this, I felt vindicated because a few years back, I was discussing freeze thaw damage in concrete and I asked about sublimation and they were, what's that got to do with freeze thaw damage? I sublimation is when water in its solid form can go directly to a vapor form and not go from the traditionalsolid to liquid to vapor. And they kind of dismissed that. And I said, I think that has an important impact on concrete durability, testing, and everything else. So when this came out, I was pretty happy. Because again, this is like another 20-year vindication. It only took 20 years this time. But sublimation, ⁓ again, is when it'sWater goes from a solid to ⁓ a vapor form. However, and this ⁓ is really interesting, they're finding now that light alone, there doesn't have to be heat to create evaporation. Now there has been discussion in the past and I've read articles that were left open and there was no conclusion ⁓ brought into the studies where they could see thatexposure to sunlight was damaging the concrete, but they didn't know why. This helps explain that because if the water is evaporating caused by light, that really puts new wrinkle into all of this because now we're looking at something that's affecting the curing process of concrete. So in my opinion, this really emphasizes why we need to move towards self-curing concrete.Seth Tandett (04:05)Yeah.Bob Higgins (04:13)Because if you've got the water buried in the concrete and not directly exposed to sunlight, and it filters its way to the surface, that's going to slow the process down. It's going to interrupt that process. And it's interesting, because ⁓ even when they're these super-absorbent polymers and all these ethylene-based materials that they're putting in concrete, that seems to be making the concrete stronger.if they would get away from the carbon-based materials and start going towards things more like colloidal silica, which can become a component of the concrete rather than a material that will break down and decompose. And we don't know what the decomposition materials are going to do to the concrete in either mid or long term. That's the way things should move. And we should go withmore more towards inorganics. And I don't know why they're staying with the organics. I guess it's because it's easier to study, but easier doesn't make the product better.Seth Tandett (05:11)Yeah.Yeah. Well, before we jump into how this relates to concrete, let's talk about what this MIT paper is saying. if you can explain, I think everybody understands what we currently think, how evaporation happens. So let's talk about what we all think what it is now and what this MIT thing is saying that is a possibility.Bob Higgins (05:20)or eruptOkay, yeah.Okay.Okay, evaporation is normally linked to temperature. The higher the temperature, the greater the rate of evaporation. That is true, but that's not the only ⁓ method of evaporation. What they're finding now is that light affects it because over 80 years, the climate scientists were puzzled why clouds would absorb more sunlight than physics would allow. And it just puzzled them. So now they're finding out with thisevaporation rate caused by the light. Now this makes sense because now it's switching over. this is, so this is being exhausted and the only thing they were measuring was what was being absorbed. So why is it absorbing so much sunlight? It shouldn't do that. Well that's because water is evaporating so it's being replaced. So that really, really threw everyone for a loop and they were not expecting that.In fact, that's not what they were looking for. What they were looking for, they were just trying to find out why that happened. So this photomolecular effect that they coined this term is now starting to explain certain things. And they're excited because this really closes a lot of knowledge gaps that we have. So this is a rabbit hole that they're going to be exploring for the next 10, 20 years.and things are still going to be unfolding as we go. As we go down this rabbit hole, what this is going to contribute to our knowledge is just amazing.Seth Tandett (07:16)Yeah. And so we're tying, you mentioned this earlier.Just trying to tie this in, because man, I pulled up this paper after you sent me the email, and I was like, holy cow, there's no way I'm going to read this thing. They had all kinds of crazy little ⁓ charts and graphs and pictures and things like that trying to explain what they're getting at. But basically, they're shining different types of light into the water and seeing what happens. And what they're saying is they discovered that depending on whatBob Higgins (07:30)YouSeth Tandett (07:50)⁓ color light they shined on the on the water they were getting different rates of Evaporation and I guess the green light was the most at a certain angle was the most The one that was causing the most evaporation Is that is that right? Okay?Bob Higgins (08:07)Yeah, that's correct.And I think even there, you're going to start seeing layers and layers and layers come out. that's something that until they break it all down, we probably should not explore that because that's going to sound like science fiction.Seth Tandett (08:16)Yeah.Yeah.Well, I have no problem with that. ⁓Talking about things like that on the podcast. So, but what was interesting is, you know, we were, as we always do, were chatting before we hit record is trying to find real world. Like you can go outside and see examples of this. ⁓ And the one example we were talking about, again, you mentioned it ⁓ briefly wasthe sublimation examples where ice and snow disappear ⁓ in a cold, you know, dry day. So these are a couple things that I pulled up quickly. So ice or snow disappears on a cold day, ⁓ a cold sunny day. So what we're saying, it skips the melting step and goes straight to water vapor.Bob Higgins (09:04)Yes.Seth Tandett (09:21)And I was like, ah, OK. I don't pay attention that much. Especially during the winter time, it's just cold, right? Everybody's cold, and you're not paying attention. What's going on with snow? But I thought this was interesting that pointed out, and it was the dry ice. Everybody goes and buys the dry ice for different reasons, but I always think people, you buy the dry ice, and you want that smoking.Bob Higgins (09:25)youYeah.Seth Tandett (09:45)appearance to do especially during like the Halloween time people are putting it out for it looks all spooky and everything but I thought that was a really ⁓ good example is like there you go you got ice and it's skipping the liquid step and going right to gas ⁓ so I thought that wasBob Higgins (09:51)Yeah. Yeah.Yeah, I likethe frozen clothes on the clothesline gradually drying. Yeah, again, that's another example.Seth Tandett (10:09)Yeah.Yeah, I've never tried that. I don't know that one.Bob Higgins (10:16)And ice cubes, if you have them in your freezer long enough, after a while, you take them out and they rattle because they've shrunk. And people go, why did the ice shrink? Sublimation. Now, it's much faster if it's in the sun. But again, that connection was made decades ago. And now, only in 2023 did they make that connection with liquid water. So ⁓ water in an ice form, that's been known.Seth Tandett (10:19)huh.Right.Bob Higgins (10:41)and I brought up the speculation about, wouldn't that happen with waters or liquids? no, no, that can't happen. Well, yes it does.Seth Tandett (10:49)Well, let's, okay, now let's jump to concrete. Now let's, let's, let's see, what are the implications of this? So in the email, you, you talked about RH testing. ⁓ do you want to hit on that and what you were saying in the email?Bob Higgins (10:53)Yeah.Yeah, RH testing, the surface of the concrete is a gradient. The top 3 quarters of an inch to an inch of the concrete is a gradient. Even under carefully controlled laboratory studies, like what was done with the Texas Transportation Institute, they finally did something I'd been hoping to see from these other labs. They did the compression value test on the concrete that was air-cured and water-cured.The water cure was seven days. both samples were within the spec of 4,000 PSI. However, when they sliced off the top one inch of the concrete, even the water cure at seven days was a full 20 % weaker than the remainder of the concrete. But in a compression test, they measure the break. They don't measure any type of a crush or compression. They only measure the break.we have, that's an information gap that's always existed. Now, I don't know how to test for that. I can't give, other than what Dr. Zollinger did, where he sliced off the top edge. And the concrete that was air cured was much weaker, I think was 30 % lower in compressive value. So we're dealing with something different, but it's all being treated as though it was monolithic.We can't do that. As long as we keep treating it as monolithic, RH testing, which tests well into the body of the concrete, past the one inch gradient, it's measuring something that's not a concern with the surface activity. And the surface activity is where the weather and durability conditions really start creating problems. recently, Australia ⁓ kind of one of the ⁓universities getting involved with this study, they're going to finally tackle why is precast concrete not as durable as it supposed to be. And they don't know why. Well, actually, I think I do. Because they stink here. The warmer the concrete is when you cure it, ⁓ the weaker it becomes ⁓ overall. really have shortchanged the durability.Concrete ⁓ cured in cold weather ends up having a much greater durability, but it's not fast enough for the construction schedules. So we've actually torpedoed the durability for convenience. So now that we look at the sunlight and what it does to accelerate the evaporation rate, now we're figuring out, OK, there's another separation between laboratory studies and outdoors.The laboratory isn't exposed to sunlight. This activity doesn't exist in the laboratory, but it exists in the field. And the field results keep coming out different than the lab. And they keep doing the same thing over and over again because they can't figure it out. This is a missing link that is so important to concrete, I can't even emphasize how important this is.Seth Tandett (14:07)Yeah.Just trying to think ⁓ how we can, I guess, prove this. I guess someone needs to, I guess, start doing these. Start doing these. Yeah, start, I guess, making ⁓ maybe slab ⁓ panels or ⁓ samples or whatever and put them outside and cover one up.Bob Higgins (14:17)That's part of the rabbit hole, yeah.Seth Tandett (14:35)and leave another one exposed to sunlight.Bob Higgins (14:38)Yeah, or get a full spectrum light where you start using at different angles to find out where the maximum value of ⁓ the evaporation rate is ⁓ under ⁓ that type of light. Because I don't think that they did this all under sunlight. I think they did this with full spectrum lighting, because I haven't seen the details of the study. But I think that we could do that with concrete.Seth Tandett (14:51)Yeah.Right.Well, again,just hitting on what you were saying before is then we're getting back to a lab study versus what we deal with outside in actual conditions. So to me, this study needs to be done outside.Bob Higgins (15:15)Yes.I would think so too, because we can never duplicate kinetics in a laboratory. You can't do it. You're dealing with thermodynamics. You're dealing with a set amount of rules and ⁓ influences. Outside, there is no set rules. It does what it does. And they'd have to do this in several areas of the country, because it's going to be different. For example, ⁓ Denver versus Southern California orover in the Midwest and in Florida and Texas. Those are all going to be different.Seth Tandett (15:52)Yeah, like everything else. So you could do, yeah, side by side samples. I guess cover one up. You got to make sure they're getting the same conditions. And then, I mean, you can measure surface cracking and curling and weight loss, right? To weight loss, you know?Bob Higgins (15:54)Yeah.It's like.Yes.Yes, exactly.And with its increased evaporation, that would also increase the alkalinity, which reduces the relative humidity in the surface. And once the relative humidity drops below 85%, the cement formation becomes accelerating in a negative way, where it becomes less and less efficient. Because right around 80%, it's only about 10 % of thecement formation efficiencies, it would be at, 85 to 90%. So I think this has a lot to do with the surface of the concrete and ⁓ reducing the RH well below 80 % within the first few days. So even when you put a curing compound on there and you get that acceleration effect with the sunlight, I think this is, again, it's going close the information gap that we have. Because why is it?well-cured concrete still suffering ⁓ strength loss. Because it doesn't make any sense until you enter this in, along with the concentration of ⁓ sodium hydroxide. So we have sun, heat, and ⁓ alkalinity increase. Those are your three elements that are going to interfere with the strength of the concrete and its durability.Seth Tandett (17:27)⁓ You mentioned internal curing again earlier, and this has got me thinking, why is, I mean, we've seen or heard good results with internal curing, but you're not protecting the surface when you're doing internal curing. So we're still saying there's going to be an issue with the top 3 quarters of an inch.Bob Higgins (17:52)There could be. But it's probably going to be minimized to more like an eighth of an inch if you have internally cured concrete. Because when you have internally cured concrete, you have water at least replacing the water that's evaporating. Without internal cure, we don't have a replacement. It's being consumed by ⁓ the alkalinity that's lowering the ⁓ RH and the cement formation. Cement formation just reduces the ⁓ total amount.So, yeah.Seth Tandett (18:20)Because we'resaying the nanocolonyl silica evenly disperses the water within the concrete better than if you just pour traditional concrete, right?Bob Higgins (18:36)Well,kind of, yeah, it's well dispersed and has to be well dispersed because a colloidal silica has its own water. So when it reacts to the calcium hydroxide or whatever it's reacting with, it spins water off. So that's replacing the waters being consumed in the other reactions. So it's a replacement. So you have basically a reservoir. And they found that out ⁓ with ⁓ absorptive aggregate.And they found with the have soaked aggregate that's surface dry, you put it in, it really helps the carrying process because it's giving water to the concrete. It's replacing the water that's being consumed by the cement formation and, and the thing that's not being studied. And it just, just baffles me. They're not equating the alkalinity with the reduction in RH, even though it's pretty obvious. And I have over 3000.tests and studies in my personal laboratory and they all speculate when they get to the end and they do not deal with the reduction of relative humidity in the concrete as caused by the increased alkalinity. Yet that is a given in chemistry. If you take 20 % sodium hydroxide solution, it will bring the relative humidity down to 78%. Well, you don't get any cement formation.It stops. And if it goes to 40%, it goes down to around 60%. So basically, you got this dehydrated, desiccated concrete that still has water in it, but the water is not available to form cement. So the presence of water is not an indication that cement formation will occur. We have to get a little smarter with this. We have to really look at the relative humidityin the first 30 days. And that's not being looked at correctly. And it's in the top one inch of the concrete that we need to focus. Because I saw this diagram given by this RH company. And they're showing that the surface of the concrete was 74 % relative humidity in a lab environment. I said, well, there's no cement formation. So even if it equals out later on, it doesn't make any difference. You have less cement.less density, more porosity in the top surface of the concrete. You showed that in your own study, and you're ignoring it. They're ignoring the chemistry. This is really helping to address the chemistry, what MIT did, because this is all chemistry. This is caused by sunlight. It created a chemical change.Seth Tandett (20:56)Right.So I guess just to circle back around this report, what are the big picture things we can take from it? ⁓So we assume isothermal, right?Bob Higgins (21:20)Yes.Seth Tandett (21:21)And what we're saying now, it'scould be, are we saying it is non-isothermal just based on the paper? Is the paper now the authority? I mean, how do we take this new information?Bob Higgins (21:30)Well, no. Good.Well, the paper shows even more so that it's non-isothermal. again, isothermal is a controlled condition. Now, we don't know what the sun's going to do, what the cloud cover's going to do, the angle of the sun, when the concrete is placed. We don't know any of that stuff. We're now going to uncharted territory. basically, there's a lot of this we're to have to start from scratch. So I said about this rabbit hole.Seth Tandett (21:56)Well, someof the curing techniques that we do now, I would think, would reflect the sunlight, right? So what are those that would protect the surface from sun? ⁓Bob Higgins (22:07)Well, it would have to be pigmented. It would haveto be pigmented water or something. again, we don't know what that will do because we've never known until the last couple of years that this effect even existed. I speculated it 20 years ago, but this wasn't known. So I don't know what it's going to do down the line because every time you change something, when you change one thing, you can change everything.Seth Tandett (22:20)One, two,Right.Bob Higgins (22:34)I don't know what it's going to do. I can speculate a little bit, but I don't know.Seth Tandett (22:40)Yeah, I was just thinking some of the spray cure stuff when you put it down is, you know, it's white. So to me...Just trying to think simply that that would possibly, well, get it, like again, we gotta test these things and see if it.Bob Higgins (22:48)Yeah.Yeah, because we don't know what the light'sdoing to that. Because again, that has never been considered. So now, even though it's reflecting the light, but what it showed in that photomolecular effect is it didn't need to absorb the light to create this problem. So it didn't heat up. It didn't do any of stuff. So it's doing things that weren't expected or anticipated. So yeah.Seth Tandett (23:16)Right. Soif we speculated an ideal curing ⁓ just based on the numerous podcasts that we've done on internal curing. if you were to take this and say, is legit, this is something that we need to consider protecting the concrete from sunlight.Either got to wait to pour your concrete till you got a roof over the top of it, which some projects you can do that, right? So you protect it from that. Or maybe you and I need to go out and come up with a pigmented ⁓ cure and that dissipates. They already have dissipating cure, but you got to have one that the color goes away.Bob Higgins (23:45)Yes.Yeah, and what's really interesting, within the last few months, I was presented with a problem job where they had bubbling in the epoxy, and it was much down the road. Well, it happened to be where there was a window, and where the sunlight came in and hit the concrete. That's the only place the epoxy failed. It didn't fail anywhere else in the entire room, except for where the ⁓ window ⁓allowed sunlight onto the concrete. This helps explain that.⁓ Well, maybe we had moisture from here, maybe we had moisture from there. Well, this, again, this puts a new wrinkle in things and I mean, people's heads are going to spin on this one.Seth Tandett (24:41)Yeah, they're paying attention. don't know. I mean, you had to send it to me. I don't know where, who's paying it, who do you think's paying attention to this? Other than nobody.Bob Higgins (24:43)Yeah.Yeah.Nobody. Yeah.So what we have to do is just if we just get one or two people start asking questions, that's the kind of thing that grows. This is a this will be a grassroots movement, basically, because we have to because there's a lot of science that's been out there for a long, long time that they're still ignoring. So this is just one more thing they're going to ignore. But the thing is, the installers and the concrete people are being held accountable for this bullshit.Seth Tandett (25:02)Yeah.Yeah.Bob Higgins (25:15)excuse my French, and they're being held accountable and there's nothing they can do about it. You can do everything right and things can go wrong and you have these influences are being ignored and not being shared and not being compensated for as the installers get thrown under the bus.Seth Tandett (25:32)Yeah.Bob Higgins (25:33)This isn't a harmless situation and ignoring it, harms everybody. It harms the consumer, it harms the owner, it harms the installer. We need to really get on this.Seth Tandett (25:42)We do.calling Dr. Belkowitz.Bob Higgins (25:45)Yeah, I'm going to be talking to him a lot about this because maybe if they can introduce, say, like a white pigment into some of this surface colloidal silica that they put down and the white pigment exhausts, that may correct this. It's very possible.Seth Tandett (26:00)Yeah, well, we gotta test it. Try it out.Bob Higgins (26:03)Yeah, again, yeah.Seth Tandett (26:04)All right, another Concrete Bob mind blowing episode. Always fun to bring you on and talk about chemistry and today a little bit of physics, right? This is physics? All right.Bob Higgins (26:14)Yeah, yeah,especially since they found that the physics wasn't adequate to explain this. That really is, I mean, that's a big deal.Seth Tandett (26:22)Yeah, I brought it up around the dinner table last night. Yeah. It's fun to see what the kids start, you know, they have no, you know, they have no guardrails, right? When you're a kid, you think totally free. So when you bring up things like this, they're like, wow, they start bringing up other things to reconsider. So, all right, Bob, thanks for.Bob Higgins (26:25)Did you?Yeah.Seth Tandett (26:43)doing another episode with me today. Appreciate it. As always, I will share Bob's contact information so you reach out to him if you're having problems that you think Bob can help out with. And you can always reach out to me if you're not sure who to reach out to to help you with your concrete problems. And yeah, Bob, thanks again. ⁓ Yes, sir. And until next time, let's keep it concrete.Bob Higgins (27:01)All right, thank you, Seth.Okay.