Concrete - Waterproofing - Durability

CHRISTINE: So yes, as I said, my name’s Christine. I’m one of the project consultants here at head office at MARKHAM in the Hawke’s Bay. I’ve been working for MARKHAM now for about three years. And so yes, happy to be here presenting about durability and waterproofing and how that links. And I’m joined today by Henry as well. Henry, do you want to introduce yourself?

HENRY: Yes, thanks, Christine. Yes, hello and welcome to everybody that’s online today. Thank you very much for joining. Yes, as Christine said, I’ve been with MARKHAM for about, time flies, I think it’s at nine years now, specializing… I did some time in the Aussie team over there and now head up the New Zealand construction project side of things. So yes, thanks for that intro.

CHRISTINE: Perfect. So yes, we’re going to keep this reasonably short and sweet today, but hopefully, it’ll be punchy enough for you to actually grasp the concept. You can ask questions at any stage, like if something occurs to you that you’d like to know more about, there is the little Q&A tool down the bottom. And so if you’re typing those in at any stage, we’ll get to those at the end of the presentation. But first of all, we’re just going to kick off with a welcome poll so that we can understand a bit more what your motivations are, and we’ll see if we can tailor the presentation as far as that goes. So yes, if you just want to select who you are and what your motivations are, and then we’ll get started. So we’ll leave that up for a few more seconds.

It’s almost an even split today. And so we’ve got structural engineers and architects and people interested in new technologies. So that’s helpful, we’re going to cover those, and all of the information should be perfect for structural engineers and architects. So yes, perfect, we’ll crack on with it. So essentially, as I mentioned, today we’re going to be talking about the link between waterproofing concrete and protecting the internal steel. So to start off with. Why does steel corrode inside concrete? Concrete can be thought of as quite an impermeable product, but it contains tiny capillaries, which are highways for moisture. And traveling on the back of that moisture is contaminants, fluorides, et cetera, that’s able to get to the internal steel and start breaking that down. And so, Henry, do you want to talk a bit more about what’s happening in terms of that steel breakdown?

HENRY: Yes. No, thanks for that, Christine, interesting topic this. Okay, we all think concrete is impermeable, but it’s actually just a big sponge. Even 40 or 50 MPa concrete, we still know that moisture finds its way through the weakest link, I guess, in the concrete. There’s also some other drivers, so what drives most concrete internal reaction. There’s a few different things here you guys probably know a little bit about, you might not, but we’ve got the standard ones here, you got ASR, you got carbonation, DEF. And just to unpack them a little bit more, so your ASR is obviously your alkali–silica reactivity, you got sand or certain reactives in the aggregate that wind moisture heads at, it obviously swells and you get breakouts in your concrete. It doesn’t always happen in every part of the world. There are some even here in New Zealand, there’s only certain parts of the country that it happens in, but it is quite common.

You got carbonation, so as long as CO2 can get under concrete, you always have problems. DEF, so that’s basically where there’s unreacted cement, or if you like, the curing process has been done too fast and the cement particles don’t react like they should and therefore cause problems down the track. So I guess that’s a few of the issues, and that’s around about our why with MARHAM, why we waterproof structures. Our mission’s adding life to concrete by providing stable solutions. Our vision is to save the world, one concrete structure at a time. And so when these problems do occur, they are occurring close to home than we sometimes like. And there are some projects, some of you will know what’s going on on the other side of the world now and caused by certain types of concrete cancer, if you like.

So we’re all about educating people on these issues. And following on, as Christine said earlier, really all these contaminants relate to moisture and concrete in some way, contaminants jumping on the back of moisture and getting in and out in concretes in wet and dry tidal zones, marine environments, moisture getting in and reacting and causing the likes of ASR, moisture getting in and reacting unreacted cement and DEF, that sort of thing. So the moisture migration is the transport system. And what we like to talk about is waterproofing from the concrete, whether it’s an existing structure or a new design, but if we can stop moisture migration in and out of concrete, we can stop a lot of problems in concrete. And that’s the start of where like to go in that essence of adding durability to concrete as really a simple solution, is by waterproofing it with the hydrogel treatments.

And you guys out there might have heard of some other treatments, the internal pore-blocking treatments, that sort of thing. The hydrogel is formed inside the pore in the porosity of the concrete. So you can see our unshaded example on the left there, you got your wet and dry and your water coming in and out. So a concrete porosity is about 50 nanometres, a human hair is about 100,000. So you can see how fine the particle is, and so hydrogel particle gets down to about 10 nanometres. So even when we spray-apply this to the surface of the concrete, existing concrete, we can get deep penetration into concrete up to 150 mils, reacts with that moisture in the concrete, that forms the hydrogel in the concrete. It’s in there for the lifetime of the concrete, and therefore stopping that moisture coming in and out of concrete, even under hydrostatic pressure. So that’s the kind of example we like to talk about. Have you anything to add to that, Christine?

CHRISTINE: No, I think you’ve covered enough. I mean, we’ve got a few ways of achieving this. We touched on both admixtures and spray-applied, where we can transform the internal moisture into a hydrogel. I think next up we got some case studies.

HENRY: Yes, we have. Yes, I’ll jump across there. Take us away.

CHRISTINE: Yes, cool. So in terms of that, the Bledisloe Wharf is one of our prime examples. Anyone who’s been in Auckland or who was watching the America’s Cup would have seen this in the background. That wharf was actually destined to be demolished way back when. And so in 1999, we were brought in to spray-apply the top deck of that. We waterproof the top, we also sprayed underneath there. And at that stage, the deterioration was quite severe. This was a remedial project, so obviously not getting in at the front end, but with our hydrogels, we were able to halt the corrosion, so it doesn’t reverse it, but we were able to hold it in place. And then 10 years later, when the checks were done, an independent engineer went and checked that. And areas that had significant deterioration showing, we have ringed it in paint and going back to check, those were completely benign at that stage of it.

HENRY: Interesting fact around that, Christine, the wharf used to be used as some type of… They use the cart some type of chemical, and there was a lot of splash over. And it basically formed the lacquering effect on the underside of the wharf. So the chlorides, they were coming up and splashing onto the top of the wharf from the sea and the waves and that, but they didn’t have anywhere to go, and the concrete started to actually trap them in there, and they were just going around and making more of a problem. And so there was a really an issue there, and it’s like putting a… In the old ways of doing it is putting a membrane or some form of bandage on there, it’s just a bandage over a broken bone, it’s not really fixing the problem, the problem is still there. So the hydrogel halts the corrosion process by really attracting those chlorides and not letting them move around the concrete because you haven’t got that wet-and-dry cycle.

CHRISTINE: Yes, absolutely. And so on the back of that success, they’re just the neighbouring… Ports of Auckland car park elected to use our full waterproofing system on the new one at Ports of Auckland. So that has taken care of business in terms of stopping chlorides coming in and out from day one. So admixtures and then spray-applied, getting a really good-quality cure as well. And in terms of that, there’s lots of options, especially for marine environments to protect them, but often they are a surface coating, which needs reapplying. The great benefit of going with this hydrogel solution is that it’s permanent, it doesn’t need to be reapplied. And that’s not going to be able to be abraded off because it becomes part of the concrete matrix and the concrete structure itself.

HENRY: Yes, interesting that you say… Also, there has been research done that any structure within, I think I read some research, within 20Ks of the coast is still susceptible to airborne chlorides. So any exposed concrete is at risk really. And yes, we just want to make sure we don’t start that corrosion process, and that whole concrete cancer then come along, do it?

CHRISTINE: Yes, absolutely.

HENRY: So seal from day one for protection. Another project a bit further from home, the Geraldton Wharf in WA. So this wharf was treated to the top and the bottom. And their requirements around that from the consulting engineers was they wanted a minimum of a 50% reduction in permeability on that structure. Obviously, we did some onsite testing there as well, some independent onsite testing before we completed the whole wharf. And there are pretty awesome results there coming in, we got about a 75% reduction in permeability. That was carrying out with the GWT pressure testing onsite. So really cool results there, and obviously adding life to their structure for years moving forward. Once the hydrogel’s directly in the concrete, you can’t wear or abrade it off, it’s in there for the lifetime of the concrete.

So we can therefore add the life, halt any corrosion process from there on out. And saying that, if there was a wharf that was starting to spall and starting to break down and exposing, obviously we’d have to work in conjunction with some repair mechanisms there. But if we can get to it early enough, where your structure’s still intact and that sort of thing, we can obviously save your clients a lot of time and money.

CHRISTINE: Yes, perfect. And pretty close to head office, this beautiful picture of a human waste digester tank. So our admixture products were utilized to waterproof the structure, but obviously, in an environment like a sewage digester tank, you’ve got a really serious risk of chemical attack to the concrete. And what can happen in these sorts of scenarios is that the waste creates a reaction with the concrete itself. And so our admixture was utilized to both waterproof and protect the structure itself from attack. Concrete is used often in these sorts of scenarios, and it can be difficult to protect it. And so our admixtures were utilized in those panels and our gasket in between, and they are still looking great and working well.

HENRY: I guess the point there is also, Christina, is that we’re not saying this is the be-all and end-all of systems, we do work in conjunction with a lot of other systems as well. In very high corrosive areas, obviously, we can’t say we’re going to totally halt the corrosion process, because obviously if we’re inside the concrete, your surface in these harsh environments will get abraded away. But what we can say is, by waterproofing the concrete, we can give it a lot more durability, and give that surface a lot more durability, so we just extend that period out more in these circumstances. But there are some pretty good results, we can send some through of testing we’ve done, and then projects we’ve done around acid smelters and things like that, where the concrete takes a really hiding.

So that is just about a wrap. We’d like to open the floor for some questions now. I’ll just close this off, stop this share. If anybody’s got any questions, we would be open to answering them, or if they would like to see any testing or any reports and such, we’re more than welcome to send that sort of thing through. So we’re a very project-focused business. And we work from design through to installation, we don’t just sell products. All these systems are installed by approved applicators that work in-house for us, that way we can QA and give the likes of a warranty, 25, 30, 40, 50 years, performance warranty to your project. So, yes, I’m opening up the floor for questions.

CHRISTINE: Yes, anything at all … pertaining to concrete and waterproofing!

HENRY: What are some of the challenges you guys had out there before in the past? And anything come to mind, challenges that you’ve had? We might add or give you a quick summary or a solution.

CHRISTINE: OK, failing that, do you want to talk a little bit more about our warranty side of things, Henry?

HENRY: Yes, no problem. So, as I said, it’s the way we give an insurance-backed performance warranty. This is QA’d and checked from our head office here at Napier. We’ve got our office in Sydney, they obviously run through Aussie projects. But we’re not just selling a pail, we’re actually here for the lifetime. We’ve been doing this for 25 years now, probably about 150,000 [square metres] per month across ANZ, New Zealand and Australia. So we’ve got a lot of track record there, but we’ve got another question.

CHRISTINE: Yes, about durability and whether we can issue a 100-year durability certificate?

HENRY: Yes, definitely. So great question there. Yes, we have actually recently done a project in Auckland with a 100-year waterproofing durability warranty. That was a conjunction of a whole project that we worked on from design through. So yes, with every project we’re more than happy to weigh up the risk and look at a project from the start and come back to you with a solution. So yes, fire us an email, and we’re happy to chat.

CHRISTINE: And there’s …

HENRY: That’s a great question. How do you convince asset owners the initial cost of admixture is worth the upfront expense?

CHRISTINE: Yes.

HENRY: Brilliant. Now, because we’re dealing with so many asset owners on repairing their existing structures where preventative maintenance hasn’t actually been in place like it should have been. So we can use that project history of the maintenance with existing structures. There is also a Tuutti model. It’s out of, I can’t remember off the top of my head, it’s out of Australia, University of Australia, I think. [Kyösti Tuutti of Lund University, Sweden] We might be able to get that up. Brendan, you wouldn’t have a copy of that there that we’d be able to show on the screen, would you? We’ll just see if our admin can bring that up.

Yes. So he’s just bringing it up. And there’s one more question we can… I’ll just answer this other question while we’re waiting for that to come up. What would work for preserving concrete stumps on the houses? We probably have to know a little bit more about when you say concrete stumps and what you’re trying to achieve there. We could treat the concrete and stop any moisture getting into it, therefore waterproof it, stopping it from breaking down. I think you must mean piles.

What is the best finish for concrete in plant rooms and fire stairs? Is this epoxy and does it work for waterproofing if required? Epoxies have got their place, they can be costly. Also, the install can be a mission, especially in plant rooms, fire stairs, very confined, going to be high fumes, you’d have to do a lot of containment. With our systems, we’ve got a penetrating sealer that’s environmentally friendly, and so, therefore, be a bit safer to use and such.

CHRISTINE: Yes.

HENRY: Hopefully that answers the question there.

CHRISTINE: They’re all certified no-VOC, so safe for installers. And for examples that we’ve talked about in terms of marine projects, it’s safe for the environment as well, they don’t need to be contained. And so yes, in terms of your plant rooms and fire stairs, it depends on the project, and we’d have a look at it and weigh on what we would recommend, but we have got full waterproofing systems.

HENRY: Sorry – hopefully you guys can see – can you see what we’ve put up on the screen, Christine? Can you see the screen? [modified Tuutti modelling graph]

CHRISTINE: I can.

HENRY: There’s a graph on the screen. Yes, cool. So thanks, Brendan, for putting that up. It wasn’t quite the one that I was looking for, but this does explain it. So you got to your exposure time here. Do you see this graph down the bottom? You’ve got your scale on the left as your damage level, and then you got your exposure time. And what they’ve … research shows that as an exponential graph with corrosion and concrete, it’s in those early stages in A and B where we like to see and have a look at structures, the first cracking, therefore. And obviously, your structure is going to move right up. And you’ve got these further lines out here. And obviously, if we can push it out more, we’re going to extend that durability.

This is another way we can talk to asset owners early on and say, “Listen, by using modelling we can extend your structure this far out.” There is also a Tuutti model [Reinholdt de Sitter’s “Law of Fives”] that says basically, if you spend $1 more at the design phase, you save up $125 at the remediation stage. And we can see in that graph to you, it’s quite interesting. So it’s not a large cost early on to put into the project to save big costs at the other end for remedials and that sort of thing. Talking about costs, we’re not a high cost either. So we’re talking about $40 to $50 maybe, a square metre for existing structures, which is pretty awesome when you can… It’s a one-time treatment for a structure, we can back you up with a 25, 30-year plus warranty, over against putting a silane or siloxane or something like that on a concrete structure where you have to come back and repair it in five or 10 years.

And when we put a patch, as I said earlier, on concrete, it’s only surface. If you have chlorides in concrete, actually it incites them, attracts them there, and it’s a bandage over a broken bone, it’s not really fixing the problem. So by putting a penetrating sealer on, you obviously, inside the concrete, fixing the concrete, stopping that corrosion. So hopefully that’s been informative for you guys.

CHRISTINE: More before we go …

HENRY: Just check if there’s no more questions there, Christine. We will send out just a questionnaire after this as well. And it will have our details on, so you can contact myself or Christine direct, and we’ll put you in touch with the right people if we can’t help you. But that’s about a wrap, I think.

CHRISTINE: Yes, perfect. Thank you, guys!

HENRY: Good to ‘see’ you! Catch you round. Ma te wa!