Easy, Sustainable and Safe

BRENDAN:

Well g’day and welcome aboard, everybody, to the latest online event from MARKHAM: Easy, Sustainable and Safe, protection for concrete infrastructure in the mining and related industries. So with us today is Doug Hamlin, who’s going to give you the pukka on all things in relation to durability in construction. There is a questions button, down the bottom right-hand side of your screen, and a chat button. We would be very grateful if you want to put any questions in there that you may have as we go along. Then we’ll have a live answer session towards the end.

Doug, without further ado, would you like to give us a bit of an introduction about yourself, and then we can take it away?

DOUG:

Yes., thanks Brendan. Yes, my name’s Doug Hamlin. I’ve worked with MARKHAM for just over 14 years, so a lot of experience through the project management space, application, right up what I do today with the advice on projects, specifications, and advising on how to extend service life of concrete structures. So yes, keen to discuss this topic today.

BRENDAN:

Very good. So do you want to give us the learning outcomes? And we’ll step forward from that point.

DOUG:

Brilliant. Yes. So today we want to have a look at the … obviously the challenges that the mining environment in particular faces; how to choose the best admixture, but best strategy for the long term service life. And then talk around the sustainability side of things, safety and ease of use, these things that come into play when you’re looking at service life and durability options.

I would note too, that this is focused on mining, but it’s relevant to other areas in the marine and civil space. Mining does have a a very harsh acid attack and chemical attack; which is, you know, if it can survive in a mining environment, there’s a good chance it’s going to survive in a marine or civil, water infrastructure, that type of thing. So if we go on to the next one there.

So firstly wanted to look at the mechanisms that attack concrete. So what are the main challenges? In the mining we’re seeing a lot of chemical and acid attack. This also includes the hypersaline water; and we’re seeing mine sites with the water from the de-watering, the groundwater coming in at around … oh it’s anywhere from about 3 times, to up to 8 times in the worst case, the salinity of, or the saltiness of sea water. So very aggressive into that environment.

You’ve also gotten the processing areas; the acid, the ammonium sulphates and everything that are used in part of the processing and part of the mine, you know, processes there.

The extreme weather. Often these mines are in remote locations. You’ve got high temperatures and then sometimes it’s tropical too, so you get the concrete absolutely saturated, and then it goes dry and you get that sort of cycling happen.

The steel corrosion; so obviously this is a result of the chemical attack and result of the contaminants getting into the concrete causing that rebar to rust and expand and pop the concrete off. This is obviously driven by by moisture into the concrete.

ASR and DEF: they are two different topics, but they work on a similar mechanism, whereby the internal matrix of the concrete expands and causes cracking, which speeds up the ingress of contaminants.

Carbonation, softwater attack. Not so much in mining, but yes, it is again, essentially a light acid attacking the surface.

You’ve also got with the mine sites, you’ve got a lot of heavy machinery moving around, so you got that load and abrasion there; and some of the materials used or that they they’re mining out. Lithium, for example, is very abrasive to concrete.

And then lastly, the material supply. So a lot of these are trucked from, say, a centre like Perth, and it could be 1-2 days into the site. So they want to limit down how much material is going to site and, you know, getting something that’s working in that space also on site; not taking up too much room; and easy to dose and use inside the concrete. It’s not causing any detrimental effects to the placing and the set times, that sort of thing.

So yes, a lot of things to think about in the space. It’s probably one of the harsher places to pour concrete, but yes, there are things we can do to overcome it, which we’ll go onto shortly. Next slide there.

So thinking about these threats and then the impact of them. So downtime is probably the biggest one. Mine sites are there to make money, essentially, out of the ore that they pulling out of the ground. If you have any downtime, that’s costing them, and they do everything they can to limit it. Concrete repair, unfortunately, is one that does pop its head up; where you get you get that breakout and repairs are done. And then because you’re not… if nothing’s done to protect that repair and protect the concrete around it, you get more of a breakout beside that repair; and it kind of cycles on like that. And you get that happening every …sometimes as soon as every two years, but normally around that 5 to 10 year time period

And then ultimately if you’re not … these threats can cause the structural integrity or the life span of that concrete to be reduced. So it’s not doing the job it was intended to, it’s not providing that foundation or that structure for the processing plant or for the mine site there.

The other thing is traditional mix designs. So when you’re looking at some of the things like… microsilica is a good example, and there’s other admixtures that can interfere with the critical properties of concrete. So things like the slumps, the set times, strengths, and those sort of things need to be all be taken into consideration when you’re choosing a durability method to overcome these threats. You don’t want to be getting high durability, but then have concrete that’s very difficult to place, for example. Go on to the next one there.

So MARKHAM recommends protecting the concrete from day one. That’s the most, or the best way to be sure that the concrete is going to get the best chance. So you’re not letting any contaminants into the concrete from day one. You’re not letting that concrete be attacked. You’re getting that protection right from the very start. So we recommend the use of hydrogels. They do a very good job of durability, but then they also fit in to the construction programme or the construction methodologies very well too. So what they do is, it’s a colloidal silica that reacts with the calcium hydroxides in the concrete, or the alkalis that are always a byproduct of the cement reaction. And they form a hydrogel within the porosity and it stops the moisture moving through the concrete.

Now as soon as you stop moisture, you stop that, or block that contamination from being able to move through the concrete. So if that was from day one, you’re stopping it. If you do have a structure that’s down the track, there are options to spray apply, and halt or arrest that deterioration at that point. But the key is that it’s stopping that moisture and reducing that permeability of the concrete, which in turn results in long-term durability. Next one there, Brendan.

So on constructability. I touched on it before, but with anything you’re doing with concrete construction, the key really the constructability, or how easy it is to place the concrete. How easy it is to achieve the structure needs, that type of thing. So we believe that quality starts there. So it starts with being able to place the concrete easily; to be able to dose an admixture into the concrete. And to be able to pump it, whether you’re doing shotcrete or anything like that. It needs to be able to fit into all those methodologies and not have any detrimental impacts or interrupt that process too much.

So with hydrogels, because they are a liquid admixture, they go into the mix water, and they don’t impact your strength, don’t impact your pumping ability or the workability of the concrete. In fact, they actually make it better, because you are essentially lubricating the mix and you’re using up more of the cement in the hydration process so you get a more workable mix. They are compliant to the 1478 type SN standards. So that that looks at all your critical things like strength, slump, shrinkage, bleed, all those things; and we comply there. So basically, if you take your standard concrete mix and you’re wanting to make it more durable, you just take that mix, add the hydrogel to it, and then carry on. There’s no need to revisit all the mix designs and everything there. Next slide, Brendan.

Sustainability and safety. This is a strong commitment here at MARKHAM. In terms of the hydrogels themselves, they are a very low carbon emitting product as far as the manufacture and freight, everything that’s associated there. And the CONQOR range that we deal with actually comes from a byproduct of geothermal power stations in New Zealand. So yes, contributes very positively there. The product itself is water-based. It’s non-crystalline so it doesn’t have any silica sands in it – sorry, crystalline silica in it. So it’s not posing a silicosis risk. They don’t smell, so they don’t give off any solvent-y or ammonia odours there. And they have a nil VOC content. So no solvents, no volatile organic compounds. So as far as being safe, it’s excellent there in terms of handling, transport and dosing, placing; everything that you need to do with the product, or with the concrete essentially, on site.

We do have the EPD declarations available there and yes, they can be put into your project numbers if you’re going for a green star type build, and yes they are published and available on the EPD website there. Just move on please.

Back to the topic of being easy to use. So I mentioned earlier, they are liquid, so water-based, liquid. They have a smaller… reasonably small amount of active ingredient with the colloidal silica. But because the colloidal silica is a nano-style product or nano-scale product, the size particles we’re dealing with are very small; compared to say something like a microsilica or fly-ash or something like that where you’ve got bigger particles. And what that means is that you get more reaction with the with less amount of product. So with … typically into concrete mixes, we’re putting between 2 and 3 litres of product per cubic metre. Now this is a lot lower than some of the powdered admixtures you’re putting in; and then also a lot lower than some of the other traditional admixtures which are upwards of 20 litres per cubic metre. So it’s very easy to put on and it doesn’t affect your water demand or anything like that. As far as transporting them to site, logistics, that sort of thing, it’s a very low cost there. But what’s more important though, is that once you put that admixture into the water, into the mix water and it goes into the concrete mixes, it is very easy to pump and place, so we’re getting regular feedback of pump pressures, being able to be lower. So at least wear and tear on the machines, that type of thing. And then that translates into being easier to rake and screed for the granos on site as well. So yes, if we could go to the next one there.

I just want to have a look at a couple of projects here. So first up, the Mount Ida project. It’s lithium and gold, and lithium is a very abrasive material. So moving around onto the slabs, that type of thing, you get that wear, it’s harsh on the concrete. Also on this site, being remote, had the hypersaline waters as well. So in the process plants, that type of thing, wash-down was all extremely high salt content. And so they used the hydrogel admixtures to protect against that. As another… or a side benefit, as you might say, it was poured in some very hot conditions, between 35-40°. Because the hydrogel is essentially hydrating the concrete and it’s holding that moisture in the hydrogel, it stops it escaping out of the concrete; and reduces that cracking, reduces the shrinkage of the concrete. So we’re not saying we don’t get any cracking, we’d be would be stupid to say that, but we get a lot less than you would with a standard concrete there. And that translates into longer service life, because you’re not having those cracks transport contaminants into the concrete and start that corrosion process. Next one there please.

Next one is the Murrin Murrin project. So this is a really a flagship project for us in the mining space. To paint a bit of a picture, the previous methodology they were using was lasting around 18 months to two years before you’d have major damage. I mean it needed to be replaced. So there’s a wide range of attacks on this project from sulphuric acid, ammonium sulphate, that type of thing. And essentially what it does is it gets into the concrete and the acid obviously breaks it down. The ammonium sulphate gets in and pulls the calcium or the alkalies out of the concrete. Either way, you get the concrete breaking down and you get like these 40-50mm gouges through the concrete. And then you’ll get say 150mm diameter pits forming in the concrete, and once they start to form, you’re losing your integrity of your slab and you need to repair or rip out and replace the concrete.

So they moved across to using a hydrogel as an admixture into the concrete. So the liquid, and then they also spray-applied to give a decent cure, but then also to provide extra protection to that top surface. They spray-applied a hydrogel as well. And then from there they were able to carry on. They always do an epoxy coating on any of the concrete in the process plants. What was interesting though is that, because with the previous system, as soon as you got a pen hole or a crack in that coating, it would go straight through and start gouging out the concrete below. When the hydrogels were used, you might get a crack or something, but it’s only attacking that very, very top surface. It’s not going down into the matrix of the concrete, and you get that gouging, you don’t get those big pits forming. Now this is for two reasons. One is the moisture can’t… the acid can’t penetrate physically into the concrete, it’s limited to the top surface. But secondly, because the hydrogel is consuming the calcium hydroxide at that first… at that pour stage, it means it’s not available for the acid or for the ammonium sulphate, the chemicals and that to attack and leach out that concrete. So yes, excellent result there.

The Carapateena project is a great example of the hypersaline water. So this concrete here, they’re getting around… not even five years before they’re needing major repairs to the plinths and the bunds and the processing plant. This is a very high concentration of saline in the water here. So yes, this is both underground and above ground. And what they’ve proving is obviously the durability effects of the hydrogel in standing up to the hypersaline water. But they’re also getting a better result off the form. So as I mentioned earlier, they make the concrete more workable, easy to use. So you’re not getting as much honeycombing and that sort of thing in the concrete. You’re getting better compaction, better quality concrete. It’s easier to move around and place so the guys can put a bit more time into the finishing and that type of thing. So essentially, it’s de-risking the concrete pour there. Obviously, again, harsh environment. The middle of nowhere and in very hot temperatures for most of the year. And then they’ll get thunderstorms and the concrete’s absolutely saturated. It gets washed down pretty much every day with the groundwater, so yes, it faces some fairly heavy challenges there. But it is standing up well and we are… it’s something we’re going to keep an eye on into the years to come. And yes, it’s a good, good example there. I’m sorry, Brendan.

BRENDAN:

No, was just going to say, yes we’d be very glad for the audience to contribute. Sorry, please do go on.

DOUG:

No, that was all I was… I was just going to say the same thing.

BRENDAN:

The Chat always asks you to ‘Say something nice’ and somebody has said ‘Something nice’, so appreciate that too, thank you very much! Just while the questions are coming in, there’s a question that always comes up in my mind. Can you say something about the permanence of the treatment, Doug? It doesn’t need to be reapplied frequently a topical coating might be.

DOUG:

Yes, sure thing. So the hydrogels, once they form inside the concrete, so whether this is as an admixture or spray-applied onto the concrete, they react with the alkalis, with the calcium hydroxides, and form a calcium-silicate-hydrate hydrogel, which is essentially the same as the binder, or the cement paste that you get in concrete. So once that reaction is taking place, it’s very hard to reverse that, or impossible to reverse that reaction. So essentially that hydrogel is in there for the life of that structure. So It can’t be removed or, you know, abraded off the surface, so to speak, or doesn’t wear like a coating; because … Essentially they are permanent. What you do need to think about is the wear and tear on the structure, loading, that type of thing and the actual design life of the structure itself is more what comes into play there.

BRENDAN:

Very good. We’ve got a question come in as to, What is the process to get this approved by structural engineers?

DOUG:

Yes, that’s a good question. So typically we go through a process of… they’ll want to see things like the strengths, the set times, all those critical properties, that they’re not going to have any impact on the structural design side of things; which – we can supply that. And secondly, it would be things around the actual durability performance. So looking at what that cover concrete – what improvements we’re getting there. So things like water penetration into the concrete, so under high pressure; chloride diffusion through the concrete matrix. So when they accelerate chloride ingress into a structure and see the resistance there. And then things like carbonation, acid testing, that type of thing, Depending … really depends on what the project is trying to achieve as to what they want to see. But yes, it’s essentially those two things; to make sure it’s not going to impact the structure, and that it is going to improve the durability. Once we show those two things, the approval was, yes, goes from there.

BRENDAN:

That’s fair enough. Thank you. And another one, here in the chat. Hydrogel samples in demo bottles that are over five years old… hydrogels in original condition. Thank you, Loch, appreciate that feedback. The micropores are easier to control, and longevity pretty well unlimited. Did you order comment on the comment, Doug?

DOUG:

Yes, that’s good. And 1 100% agree. The hydrogel demo that we do is fairly accelerated and it makes a lot of gel in a sample bottle. But when you’re talking about concrete microstructure, you’re talking in microns, and nanometres size, and that gel is, you know, is formed in those in those pores and porosities. And yes, agree it’s even… It’s a lot harder to remove from those micropores. And yes, pretty much impossible, or unlimited, as you say, agree.

BRENDAN:

I’m just wondering perhaps if you’d like to say something, Doug, about, If somebody’s involved with marine structures or perhaps a local council, what sort of situations and what are the extreme environments needing special protection, such as similar to what you’ve been talking about in the mining space?

DOUG:

Yes, sure thing. So firstly, in the council space, it’s around water retaining structures. So the hydrogels, the way they work is they waterproof the concrete. So in water retaining you, by waterproofing the concrete, you’re stopping that moisture getting to the reinforcing steel. A lot of the times you’ve got chlorine used in the potable water. It might be, if it’s in a waste-water environment, you’ve got hydrogen sulphide attack. That type of thing. But if you can stop that moisture from penetrating into the concrete, again, you’d limit the attack to that very top surface and essentially slow it down.

In the marine space we do a lot of projects on the coastal side of things. So in wharves and pontoons jetties, that type of thing. Where it’s about protecting against that wet-and-dry, or tidal zone, where you get the corrosion happening; because it’s essentially every time tide comes up, it loads the concrete up with salty water or with chloride and that generally increases over time and you get that corrosion process, the spalling and the breakout of the concrete. So that can be used to prevent that from happening, prevent that ingress from happening. But also if you are repairing a structure – to protect those repairs and stop that cycling effect happening. So if you think about, when you do a repair, the concrete around the repair is still coming up as worse condition the repaired area. And if you’re not doing anything to stop that carrying on that process, it’s going to keep cycling. So being able to stop that moisture moving and those… in that area between that repair and the parent concrete, stops that corrosion process from progressing.

So yes, that’s a couple. There’s obviously many, many project scenarios; and that’s what we encourage as a company, to talk to us about your particular project. There’s some cases we will want to be a part of an overall solution with other products and other repair methodologies, that sort of thing. And then there’s sometimes where if it’s more as a prevention, we can just use a hydrogel and you know you’re protecting the structure from that sort of thing. Obviously from day one, using the admixture in the concrete is all you’re. needing to do there. So yes, hope that’s helpful.

BRENDAN:

Yes, that’s good. Just a further comment from Loch on the chat in regard of corrosion, mentioning that the hydrogen doesn’t actually remove the moisture for the concrete, but does stop the wet-dry cycle …

DOUG:

Correct, yes.

BRENDAN:

No oxygen is getting in, particularly below sea water. Stopping the oxygen, which is a key to what hydrogel does.

DOUG:

Correct. Yes. Yes, that’s an important point. So we’re not removing the moisture from the concrete. So  we’re holding it in there in the form of a hydrogel. What we’re doing is creating a state where that moisture is not harmful to the structure, so it can’t move around and it can’t contribute to that corrosion process. Another way to look at it is, if you think about the corrosion of reinforcing steel like an equation. So you need moisture, oxygen and some form of aggressor. So chloride or an acid or something like that. If you’re taking away that moisture out of the equation and reducing the oxygen to the corrosion process, you’re taking away the two factors or the two necessary factors for that corrosion to happen.

BRENDAN:

Yes, that’s good. Well, if everybody’s OK with that we might just walk to the summary; and do you want just touch on the points again, Doug, so they’re fresh in everybody’s mind?

DOUG:

Yes, sure thing. So in summary here, the hydrogel admixtures are a great use in the mining environment to extend the service life of structures. So the safety side of things, they are safe for both storing and dosing and then also on site when you’re placing and pumping that type of thing. In terms of sustainability, they extend the service life of concrete structures, and getting the most out of your structure from day one, you’re doing the best you can by stopping that moisture getting into the concrete, stopping those contaminants getting in from the vary start. Then the maintenance side of things. So there’s repair cycles we talked about. You push them out, so they you’re not having that happen as regularly as they were happening. So you’re reducing that downtime, reducing the costs associated, and interruptions to the structure or to the operation that the structure’s in.

So yes, thank you very much for attending today’s webinar, I appreciated the questions and your attendance. And if you do have any further questions or projects you’d like to discuss, you can reach out to us on the website or there’ll be a follow up email to this event Yes. Reach out and we’re happy to discuss.

BRENDAN:

Thank you very much, everybody. Appreciated the inputs that came in, that was good. And yes, as Doug says, we’ll share the contact details in a follow up email and be glad if your feedback. Thanks everybody. Have a great day.