Hypersaline Water - The Challenge for Concrete

BRENDAN:

OK! Welcome aboard everybody. Thank you very much for joining us today. Today’s online event is around hypersaline water – a serious challenge for concrete infrastructure.

We’ll just walk through some housekeeping and the agenda items. So we’ve got on board with us today Doug Hamlin and Hayden Prestidge, our experienced presenters.

Doug, do you want to give a little bit of background about yourself?

HAYDEN:

I can probably introduce Doug while he’s sorting that out. Doug’s been with us for 14 years, I think, now. And a large array of topics through there but now very focussed on the civil and mining infrastructure scope; and we’re very thankful for Doug’s technical background.

And then myself, Hayden Prestidge. Good to see you all. Thanks for jumping on. I’ve been with MARKHAM for – coming up ten years now. I came out of the construction industry, but very concrete focussed now on commercial, infrastructure, mining projects across Australia, New Zealand.

So thanks for joining! Brendan, back to you.

BRENDAN:

Yes, thank you very much both. And I’m Brendan Stead, and I’ll be dashboarding here today. I’ve been with MARKHAM for about ten years in a variety of roles. Now, if you have a look in the bottom right of your screen, you should see a little circle with that question mark in it, labelled ‘Questions’. And there’s also Chat button there. If you’d like to drop any questions you have along the way in the Questions button, we’ll have a session at the end where we try to answer as many of those as possible. But just right now in the chat box, could you just share with us, what your background is, what industry you’re coming from and so on? We’d love to know.

HAYDEN:

Yes, Thanks. I’d just back that, really would encourage that. I know a lot of you on here have a very, very good background, very technical sound knowledge. I’ll be really interested in your questions and comments through this. So please do that, if you could put some info in the chat now. It just helps us to tailor and think about, what type of environments you’re coming from and what we need to address.

BRENDAN:

That’s excellent; civil construction, including desalination; mining in a hypersaline environment. Civil construction manager. Good to see what’s coming in there. That’s good. Thanks.

HAYDEN:

Thank you very much. Yes.

BRENDAN:

Let’s keep that going and we’ll try and play along as we go. Just on the learning outcomes for the event.

The three main questions are,

• Why is hypersaline water a challenge for concrete?
• Where do the issues most commonly come from?
• And what can we do for protection and durability?

Hayden, if you could take us away. Why is hypersaline water a challenge to concrete?

HAYDEN:

Thanks, Brendan. And thanks again all.

So let’s look at what hypersaline water is. First, as a component. So saline obviously means salt, salty; and often used to refer to a solution of salt and water. Now the ‘hyper’ bit comes in because the concentration or the solution is so high, it’s a technical term referring to that. And generally around 3 to 4 times – it can vary, obviously – that of salt water or seawater. And so you can see that build up, that high concentration of salines and the chloride and the sodium chloride. So there’s other salts, obviously, that come along with it. And as do many other minerals, sulfates, heavy metals, all those sort of things that come along with that type of water. But we’re really focusing in on the hypersaline aspect in this session.

And along with that, with this water, it does have very high acidity levels. So the acid is, again, a key component of why we need to protect concrete, those sort of things. And it does play with the pH level.

So all these aspects of hypersaline water are really a condition that can have detrimental effects on concrete. So let’s look at that now.

So that’s sort of outlined what hypersaline water is; a very high concentration of salt and water. So that’s where MARKHAM  really comes from. Our sole purposeis to add service life to concrete. And that’s why we often think about this. How does this sort of environment affect concrete? And what’s the issues here that we’re trying to protect? Concrete is very porous,you know, at a microscopic level. And this hypersaline does carry, into the concrete. And it builds up. And it can eat away the cover concrete. So it really damages your structural integrity. It leads to that sort of premature deterioration of the concrete cover.

Now, as you lose cover on the concrete surface, it just becomes more and more porous, allowing more contaminants. And obviously gets through to the depth of steel. We see things like expansion, cracking, spalling, breakouts, obviously, leading to all those or stemming from this environment. It really breaks down the strength, the acidity starts eating away and plays with the concrete there. And then along with that you get, you know, sulfate attacks etc, which leads to that expansion cracking etc. And all these, all these things decrease the life of a structure and really pull back its durability and its ability to do what it needs

to do to perform. With that also it does bring a lot of maintenance issues and ongoing maintenance problems and as you would know and we know, taking the structure offline, especially once live or full of water or operating, is a costly exercise.

So that’s really how it affects… But really, I suppose we want to focus on the structural integrity. And what type of projects or what type of structures? Let’s have a think about that.

So if we can just jump to that next slide – Where do these issues occur? And it’s good to see a number from the mining industry here because this is a very common one. And you think about that water that’s coming out of the ground, the bore water; often full of, very high concentrations of salts, so hypersaline water coming up, bringing with it all these minerals, sulfates, heavy metals etc, that can come and attack concrete.

Also, you think about the, return water of, you know, processes that are used through mining, often obviously going back through to the tailings dam and things like that, and very high concentration often, multiples of what you’ll find with typical seawater.

Local councils and water authorities is a big one, so where they’re treating water. Not only … even into like the wastewater type scenarios where you get that acid attack in concrete, but also even soft water, potable water will have some effect on concrete.

Desalinization plants is a big one. Obviously you are working directly with salt water, and that build up, that brine; and that protection needed or that need for something to give it more life through that.

And then obviously coastal environments is where you get that wet-and-dry cycle. As with any of these structures, actually the wet-and-dry cycle is is a big player too because you get that wash and then you get the hypersaline going through it and you get that build up and loss of cover.

So that’s the sort of structures we’re thinking of. No doubt you might have a couple more on your list still. Feel free to put questions in as we go as well.   So that’s some of the challenges, that’s some of the challenges we’ve looked at what the, what the hypersaline is. We’ve looked at what type of projects it does, but let’s have a look at what can be done. So Doug, hopefully you’re ready to roll now.

DOUG:

Yes, how’s that sound?

HAYDEN:

Good. Good.

DOUG:

Good. Yes. Thanks Hayden. That’s a good overview there of the hypersaline. I guess first and foremost, it’s really important to understand that while concrete looks a solid waterproof material, it’s not, at a microscopic level. And this is because as the concrete forms, as it cures, the bleedwater escapes out of the concrete and you get left with a porosity or, you know, pathways in the concrete that moisture can get back into the concrete. Obviously there’s a lot of good efforts that go into, you know, design, constructing the concrete, making sure the mix designs line up with codes, all those sort of things. But even with all that you still get this porosity in the concrete. It’s just the nature of the material. So with that, thinking about that moisture or thinking about those pathways, they carry moisture through the concrete and the impact of that is that it also carries contaminants through the concrete as well. So such as chlorides in a marine or in a hypersaline environment, these could be many other contaminants that get carried into the concrete and move through these porosities as transported by the the moisture there.

So it’s really important when you’re talking about concrete service life to close that porosity or seal that porosity up and that’s where we at MARKHAM come in. Our technology that we work with; the hydrogels, the colloidal silica particles, they work to seal that porosity out. They form a gel inside those pathways, and you know, stop that moisture transmission from the surface of the concrete down into the matrix. Which does two things. It stops the contaminants getting into that matrix, that cover concrete; and then it also prevents contaminants getting down to that reinforcing steel and starting that corrosion process.

Now we do have a … we’ll cover it off a bit later on. We’ve got a report that looked at a car park in Vancouver that goes back to the early ‘90s. And this was looking at both the acid rain that they get there and then also the de-icing salts that you know get tracked in on the car tyres and proving some very effective durability performance there. So we’ll look at that again shortly.

The preventative maintenance topic – as many would be aware, being in the engineering, asset management space, the earlier we can get on and protect something or prevent something from happening, the better. The thing with concrete deterioration is that it’s a self feeding cycle, so it’s not a gradual or linear… it doesn’t progress linearly. It’s exponential degradation that happens. So once you start getting that damage start to manifest that it moves very quickly to, you know, cracking spalling, starting to, you know, need major repairs. That type of thing. So that’s really highlighting the need to get that protection on. Ideally at day one with admixtures. You know good concrete design. And then if you don’t get that window, protecting it as soon as possible after that, before that damage starts to really show. And that gives the best outlook, best service life expectations for that structure. So just on that, we’re not saying with the hydrogels that we completely stop any attack, or anything like that, but we push that curve as far as we can in terms of the service life and give that structure the best chance of a long service life.

Right, now this is some facts and data. I’m sure what everyone’s going to be interested in. So we’ve just done some recent testing alongside with our hydrogels, the AQURON 300 and CONQOR B50 alongside Caltite. Now Caltite is a very well recognised and high performing admixture in the market there. This is not in any way to downplay the performance of Caltite. It’s a very well respected admixture and commonly used and that’s why we wanted to do some trials up against it. Now these were carried out independently with Boral. Firstly we looked at some field testing, which, as we all know, has some challenges with variability. You know, concrete testing, that type of thing. But what it did show is even with those sensitive mixes, we were still able to get good results with the AQURON 300 in that example. With some significant improvements both in the water penetration and chloride diffusion. Strengths were much of a muchness there. Then we progressed to the laboratory testing, which was… we looked at strength again and the water penetration. As you can see there, in that controlled environment where you haven’t got that variability of the field, we are on par with the Caltite admixture there, so performing very similarly. And what’s interesting is even on a nearly 80 MPa concrete, you’re still getting that 7mm of water penetration into that concrete. That’s using the British Standard 12390-8, which puts samples under a 50m head pressure. So yes, it still demonstrates that it’s got that porosity; and then you can see the subsequent reduction in permeability there.

There is a couple of other things when we’re dealing with durability and mixtures, waterproofing admixtures in this space and that’s the workability. So the mixing and placing on pumping, that sort of thing shotcreting on site. And with the hydrogels, they are friendly towards those attributes and you do get a very good mix with limited or heavily reduced cracking compared to some other mixes out there. The handling and logistics factors – so that’s the safety and looking at the safety around dosing, that type of thing, and the physical quantity of admixture required. There’s some very good advantages there with the hydrogels, you know, being a nil VOC and potable water safe admixture. To be able to be used safely by your teams, by the staff there and then obviously not have any negative impacts while they’re pumping, placing on site. So yes, I think that’s enough on that one, if we could move on.

Just wanted to talk about a few projects now. So one project we’re privileged to be involved in is the Carapateena mine site in South Australia. Now this has very high levels of hypersaline water and we’ve been involved in protecting the new structures both underground and surface. And you know, providing that good quality concrete right from day one. So it places well, you get limited cracking, those types of things. Couple that together with the fact that you’re getting a waterproof concrete that protects against that hypersaline water from getting into the concrete and breaking it down from inside. Hayden, over to you.

HAYDEN:

Yes, cheers. And thanks for the questions that have come in. We will make sure we answer them at the end so keep firing them into the questions or the chat down the bottom there, bottom right. We’ll get to them soon.

And so if anyone’s on the call from the Sydney area they may well recognise this Anzac Bridge. But Glebe island. Now that why we’re talking about this one, it’s really interesting. Obviously it’s marine environment; and it was actually used to load salt onto, so actually had raw salt sitting on it. So that combined with obviously weather and the moisture, the seawater, etc, really harsh environment on the concrete. And we got involved to treat that. So existing structure now, we’ve talked a lot about admixtures; now this is an existing structure; being able to spray apply to the surface and penetrate and close that porosity to existing structures has been very beneficial as well, to the point now where this wharf has actually been repurposed for, like, a multi-use site where they’re getting their extension of life out of it. So being able to take away the moisture out of the equation, stop the chloride ingressing or elevating  in levels and really halting that corrosion cycle, and pushing that that curve out that Doug was speaking of earlier. So extending that service life. Back to you for another mining one.

DOUG:

Yes. Thanks. So another site we’ve been involved in is the Mungari Evolution mine site. So again, challenges with the hypersaline groundwater. This is a recent extension being conducted there and obviously being about 20 minutes out of Kalgoorlie, there’s some challenges around the hot weather; pouring in some very dry, hot conditions. So being able to provide admixtures that didn’t contribute negatively to that and gave a good result in terms of the placing pumping, not disrupting the standard concrete mix design, that type of thing; and getting that good result from day one. And then again being waterproof, protecting against that saline there.

I noticed Hayden mentioned earlier in the presentation there was the wet/dry cycling. This is very common on these type of projects. So we have got areas being washed down daily or every couple of days with the hypersaline water and you get that wet/dry cycling, even you get a bit of heat to the very saturated concrete. Then it gets very hot. It’s very harsh for the concrete in terms of, you know, breaking down that microstructure, attacking the concrete and, you know degrading that durability, that service life that you would normally expect to get, you know, in, in normal conditions.

Back to you, Hayden.

HAYDEN:

Yes, thanks. I was just thinking that even you see it where you’ve got a flow of water against a tank wall or a pipe, very easy to see the loss of cover over some time through that period. So that wet-and-dry sort of type cycle.

Now this is the one that Doug referred to earlier. Obviously we’ve done a lot through the marine sort of… mining infrastructure sector, water treatment etc. But what I just wanted to just quickly talk about this one was, this dates back a long, long time, before MARKHAM were actually involved with hydrogels; we’ve been involved with them for about 30 years in Australia and New Zealand. Protecting concrete. But this here is an old structure in Vancouver, and obviously the acid rain is a component there, but also de-icing salts. So obviously they’re good for what they do with snow and making it safe, but very harsh on concrete. But what was looked at here was there was a side-by-side comparison of a hydrogel treated concrete versus an untreated area. You won’t be able to read that report properly, but essentially what it says – it’s by Gordon Spratt. It’s an independent engineer going back to this, and it was after 18 years in service. So all through those cycles that we’ve just been speaking about; and the treated area was still being able to see the original profile of the concrete finish; so the trowel marks and how it was left as finished. So that was how it held up and its durability compared to the untreated area that showed very, very, a lot of wear over that period of time, so a clear example. And the report to show that side-by-side. So hopefully that makes sense. It just does probably… just helps to show the long-term durability or the long-term effect. It’s not just extending your service life for a matter of the first component or the first period of time, but it’s that long term effect. If you can protect that cover concrete, you’re getting a lot more out of your structure – if that makes sense. Back to you.

DOUG:

So the last project we wanted to have a look at here was the Murrin Murrin mine site. This is a very unique site; has some very harsh conditions. Obviously the hot and dry, windy, and the processing plant there has some very aggressive chemicals, shall we say, and what they were finding is, that the damage that you can see in the left there and the pitting and that cracking, the gouging out along that crack, there was happening at around the 18 month to two years period; and it wasn’t long from there that they would have to be breaking the concrete out and replacing it; as it was bunded areas they needed to have that protection from, you know, those chemicals getting into the ground. So they switched across about five years ago to the hydrogel admixture. They also spray-applied with a hydrogel curing treatment. And then obviously carried on, did the epoxy coating following that. And what’s really interesting is you can see in the right-hand picture there just below where the arrow is pointing is a crack; and normally what would happen is that once you would, it would, the chemicals would get through the membrane and get into that crack, you would start to see the damage that you’re seeing in that left hand picture. With the hydrogels, because it stops the acid, stops the chemicals going in past that very top surface and stops it going horizontally into the, you know, spreading in the concrete matrix. You get a lot better of service life out of that concrete; so that damage mechanism that you would normally see isn’t happening in that that environment there. So yes, again, this site was aggressive chemicals, acids, that type of thing, the washdown water. I’m not sure on the salinity of this here, but I’m imagining it’s high. And also has other chemicals by its nature. And it’s getting getting washed down regularly. It’s got it’s having to deal with, you know, leakages spills, that type of thing. And so yes, very harsh environments and a real true testament to – if you get that concrete sealed up and that porosity blocked, you go a long way to getting a long service life or getting the best service life out of the concrete.

Well, I think that pretty much wraps us up back to you, Brendan.

BRENDAN:

That’s really good. Thank you very much Hayden and Doug; and thank you too to everybody who’s been putting entries on the questions and the comments. Good to see some familiar names in there. Great to hear from everybody. We’ve just got a few questions come in here, if you wanted to… I’m not sure who to address them to. We’ve got one saying, What’s the best time to apply this on concrete? We may have passed through that little bit in the presentation. What would you say, Doug?

DOUG:

Yes. No, that’s that’s a good question. So first up if you can use the hydrogels as an admixture in the concrete, is the best. So you’re getting that protection from day one, from the day it’s poured. But if you do miss that window, or if it’s, you know, damage starts to manifest further down the track, or it’s unexpected, whatever it may be, you can spray apply hydrogels at any stage of a structure’s life. It more comes down to, you know, whether it’s worth it from an asset management point of view. If it’s just starting to manifest or you’ve just done some repairs, that type of thing, that’s the perfect time to apply the hydrogels and get that, stop, stop those damage cycles happening and  that service life out. You got anything on that, Hayden?

HAYDEN:

No, no, that’s right. You can go to any age concrete. As long as there’s access to the bare concrete. So if there’s a curing or coating that’s been put down that would need to be removed; but yes, we can access any age concrete, so that’s good.

BRENDAN:

Very good. Just got a question around, What was the dosing rate comparison versus the Caltite?

HAYDEN:

That’s an interesting one; that’s a good question. Because that is a consideration, especially in remote sites where … or just general logistics. Now generally – we work with the dosage rate and we work on the cement content of concrete. But generally we are between sort of 2.5 to 3 litres of product per cubic metre. And I think that’s a question about the comparison to Caltite. I think they are somewhere around the 30 litres per cubic metre, so a lot more products, or it’s 10 times, or 10 times less for the hydrogel to go in. Hopefully that makes sense, clarifies that. So a lot less logistics from even a freight point of view, getting it to site, all those sort of things. Yes.

BRENDAN:

We’ve got a comment around the chloride diffusion values shown, being quite high for high durability content concrete. Didyou want to speak to that, Doug?

DOUG:

Yes. Yes. No, I agree with that comment. The challenge there was dealing with a remote site and conducting trials there. Obviously you don’t have the controls and things that we do in a laboratory situation, but what I would say is that even when you have got those factors that you don’t have control over in a lab, you’re still showing good results there. You know, as far as the comparison goes. And yes, we’ve definitely been back and given them some advice around the mix design, things like that because there’s some improvements that can be made there for sure. So appreciate that.

HAYDEN:

Yes, I agree with that. And we do realise that, thanks for that comment. Probably the other point on that, Doug, it does show also the life example of the actual conditions or the actual concrete we see in the field versus what we’re doing in the lab, but we are always running lab tests as well and appreciate any input into getting these as per results you want to see. So it’s good.

BRENDAN:

OK, now we’ve got a question around comparison versus certain Xypex products. I wonder whether that might be something we could perhaps take offline regarding specifics if that’s all right?

HAYDEN:

Yes, I’ll just touch on that quickly. I was just looking at that question, just touch on that quickly. Obviously, there’s a lot of powdered admixtures out there which have been sort of the traditional approach. And that takes up a lot more moisture and can lead – if it’s not cured right and not worked and placed right it can lead to excessive cracking or unexpected cracking and drying shrinkage, those sort of things; and workability, placeability. So you’ve got to be careful about that with your mix; and yes, absolutely we can send an example for that, but more than happy to follow that up offline, yes.

BRENDAN:

There’s a question on, Whether it has been used in conjunction with shotcrete and underground ground support? One of those case studies had an underground structure, Hayden? Was that shotcrete, or…?

HAYDEN:

Yes, we actually do a lot with shotcrete. The beauty of it is, it can be, it pumps very well, to the point where they can actually pull back on some pressure on their pumps. So you can reduce things like your rebound and stuff as well. So you get a better concrete out of it overall. We have added it both at the nozzle and through the concrete mix. So 100%, we do a lot with shotcrete; and those underground and get that… Because the hydrogel is set up right from the start and reacting with the alkalines and the cements and the water in the concrete, you’re effectively waterproofing from day one, so you’re giving that protection to the concrete and to what you’re protecting against right from the start. Any more comment on that, Doug?

DOUG:

No, no, other than, yes, just to highlight what you said, the workability, lowering those pump pressures, things like that, there’s some good advantages there. But yes, 100%, can be used and has been used and that situation.

BRENDAN:

Very good. Another one for you, Doug. Is it compatible with ammonium nitrate?

DOUG:

Yes, I’m just thinking about that question. Is that… in terms of, if that’s being exposed to the attack from there, it’s probably something we need to do a little bit more work on there, but if it is a contaminant that gets into the concrete. And it breaks it down that way, stopping that moisture transferring into the concrete is what the hydrogels do and you do see that protection there. We probably need to get a bit more info on that one.

BRENDAN:

Follow that up afterwards. Now I’ve got a question or a comment around the Murrin Murrin case study which had issues with ammonium sulphate. Most acid and ammonium sulphate areas are protected by coatings. Were the deterioration issues related to failure of the coatings?

HAYDEN:

Here we come.

BRENDAN:

There we go. Sorry, Doug, did you get that question?

DOUG:

Yes. Yes those areas do have coatings. What we did notice in those areas was because they were putting that on fairly quickly after the concrete pour and the concrete wasn’t getting a good result in terms of, you know, there was a lot of cracking, that type of thing with the weather, the environment there; and when they go to put the coating on that obviously doesn’t help the service life of that coating. But what I do want to highlight, and we covered off earlier, was that there’s areas where you can see where those chemicals just go through that membrane and start pitting out the concrete and gouging out the concrete in those areas, which is not … it’s kind of related to the cracking, but it’s not. If that concrete was waterproof and protected properly, you shouldn’t see that gouging and that pitting of the concrete; and that’s what we were able to prevent or, you know, significantly slow down to the point where you only see a very thin line, or very localised point where that’s gone through the coating there. Another point on that was the bond that they were getting between their coating and the hydrogel treated concrete was a lot better than what they were getting with the previous crystalline admixture and curing membrane that they were using there. So yes, there is always a few factors that… it’s always kind of a package deal, if you like, to getting a good service life, good durability concrete there.

BRENDAN:

Very good. There’s a question round desalination plants. One of the issues with reject brine is a combination of elevated sulphate and magnesium. Think that’s in your court too, Doug.

DOUG:

Yes, that is a that is a common factor there. So with the even in seawater you do get some sulphate content, that type of thing, obviously it’s elevated and this brine and the brinewater situation. And with sulphate attack, what happens is that it gets into the concrete; again, helped by that moisture; and breaks down that surface and scales off the surface. Now if there’s no moisture to feed that ettringite formation or that scaling, that expansion forces of that sulphate attack, you go a long way to preventing or slowing that attack right down. So that’s, I guess, another advantage of a high durability, low permeability concrete that you protect against those that sulphate attack. There’s actually a good article on our website that we can probably include in the follow up email to this event, that goes over that very topic as well.

BRENDAN:

Very good. Just a comment again around chloride diffusion values, which probably relates to the discussion earlier. A question on, Applying to existing concrete, can you paint over it? Then a question on abrasion resistance and stormwater concrete pipes.

HAYDEN:

Yes, good. Good questions. I can talk to those, maybe. A coupl of things in there. Compatibility is a big topic. We probably should have covered that earlier. So it’s good question. When we’re applying to new or existing concrete, you know, what the subsequent coatings, adhesive paint, line-marking, floor coverings. All those type of things. And thankfully, we can say we’re compatible. We’ve done this… and especially in the floor coverings market for 25 years plus. So a lot of different adhesives, paint-ons, epoxy coatings, all those sort of things have gone over us. Why that’s what it is, it’s we’re colloidal silica based. So essentially we are just creating more calcium-silicate-hydrate in the concrete. So that’s already in the concrete. We’re not adding the adding in anything foreign, if you know what I mean, that will react with your paints or subsequent finishes. So there’s that point.

Abrasion resistance is a good topic. So a big part of what MARKHAM does is even into like the car parking space or warehouse logistics type space. But also for you know these hypersaline type environments where abrasion… you know, trying to increase that abrasion resistance; and probably just looping back to that. There’s two things. We’ll share a Brisbane case study where we had a side-by-side example after this. But also just looping back to that Vancouver report, where there’s a clear… You could still see the original finish, the trowel marks or almost like broom finish type example versus untreated area where there’s a lot of wear. So not saying that would keep that profile forever, but would just extend that service life and make that top surface a lot more durable, so increasing abrasion resistance, yes.

And then stormwater, wastewater pipes, all those sort of things; yes, we have done a lot of that over time. Obviously, precast does have a tighter finish. It’s a more closed-off porosity, but we can still, due to the nano size of the particle of the colloidal silica, we can still get into those environments and protect those type of things. Best to do, if possible, is include it in your mix when you’re doing precast elements and get it right through, that protection, hopefully. Good question. Thanks.

BRENDAN:

It’s very good. I see we’ve just got a couple typing… here we go. Question: Are the products industry approved? For example Transport NSW or RMS B80 spec. That’s been part of your domain in the past, Hayden.

HAYDEN:

Yes. Interesting. We do a lot of work with a lot of different roading authorities actually. Transport NSW, we do a lot of their structures. As far as the RMS B80 specification, that’s quite specific in what it’s looking for. But in saying that we have… And yes, I’d like to talk more, or if you got project specific on that one , it would be interesting. We have done a lot of work there. Same with like TMR, main road structures across New Zealand NZTA, things like that. So we have got a vast track record with roading infrastructure.

BRENDAN:

I think we’re pushing a little bit for time. I think there might be one more question coming in. Is there any modification to the mix design required, particularly when using superplasticizers? Does the hydrogel modify the slump, for example? It’s a good question. And no, it hasn’t been covered already. Either of you, Hayden or Doug could take the one up.

DOUG:

Yes. So, no, that’s a great question. That is one advantage with the hydrogels is that they work with your approved mix design, so if you’ve got an approved 40, 50 MPa, whatever it may be, mix design, we can be added to that mix and you don’t change any of your water reducers or superplasticisers or anything like that. Just keep everything the same. There are situations, as people get more familiar with it, that they can pull back a bit on some of those superplasticisers, that type of thing, but straight up we wouldn’t change anything there.

And in terms of the slump, it’s much the same. But you need to be aware that when you’re adjusting slump, you often don’t need as much water added to that, to increase the slump more. So it is a bit more sensitive than a controlled concrete there; but nothing that’s not workable with what you’re doing out on site, type of thing.

BRENDAN:

Very good. I think this might have to be our last question. Thank you very much, and it’s my favourite. If we hadn’t had any questions, I would have asked this one as a stock standard! What is the lifespan, do you have to apply every five years?

HAYDEN:

Absolutely! No! No, that the beauty of it. We probably should have covered it. It’s permanent treatment. You can’t reverse it. As I was saying earlier as well, what we’re doing inside the concrete is building more of that calcium-silicate-hydrate. So it becomes permanent, becomes part of the concrete, part of the structure; and it’s not a re-application, it’s not something that’s on the surface, it’s all internal acting. So it’s not subject to, like, wear, or what’s happening on the surface at all. Protecting the concrete integrally and therefore no, no need to re-apply. And a lot of life examples of that now, especially in marine sector, wharf structures, roading structures, right through commercial construction, a lot through. So a lot of … that’s a good question. But especially thinking of … You know, you get a lot of different maintenance products, coatings, say like siloxanes, you know, even talking about cathodic type protection, those sort of things, where it comes with the maintenance schedule. And thankfully we haven’t been… with this product it’s not needed. That’s good.

BRENDAN:

Excellent. And thank you very much to you both, Hayden and Doug. And for everybody who’s joined, and brilliant interactions. Very much appreciated. If you have any other questions, we will be sending out a follow-up email with contact details to come. So you will be able to get in touch with us afterwards, with any further questions that come to mind.

DOUG:

Thank you.

HAYDEN:

100%, thanks for jumping on. Yes, it’s brilliant. As Brendan said, please give us some feedback too, but yes, we’ll put our email addresses on there. Fire back anything. Or if you’ve got some project-specific stuff? There was a couple that came into the chat so give us some detail. Thanks all.

BRENDAN:

Very good. Thank you. Have a great day.