Optimising for SCMs

BRENDAN:

Well, g’day and kia ora everybody. Welcome aboard our latest online event from MARKHAM. And we’re today talking about optimising for SCMs; meeting the needs, the challenges of supplementary cementitious materials. And with me, we've got Hayden and Christine. And just in two moments I'll share the slide deck. I promise you it won’t be death-by-PowerPoint! We've got it fairly short.

Is everybody hearing us OK? Do you want to just drop a note into the chat that we're coming through OK?

So we've got Hayden Prestidge and Christine Melville. Some of you will have met these characters before! They’re in our Napier office in MARKHAM, and they'll introduce themselves in more detail when we get to it. And as mentioned, we do have the chat box down the bottom and a questions box as well. So we'd be very pleased if you'd like to put your questions or comments into the chat.

We want to keep this as interactive as we can. So the agenda today:

[1] Why SCMs, and why now? Carbon, codes and what's changing.

[2] Getting the mix right: practical optimization of high SCM concrete.

[3] Proving it! Performance, compliance, and EPD backing.

Christine, take us away. Why SCMs? All right. What even are SCMs? - if you'd like to give us a bit of explanation - and why now?

CHRISTINE:

Kia ora. Sure. Thanks, Brendo. Hi. As he's introduced already, I'm Christine, based in the Hawke's Bay office at MARKHAM. I've been here for seven years now, and my space is mainly around the designing. So early... Engineers, architects and that sort of early-work space.

So again, in terms of why SCMs, and why now: obviously there's been a huge industry push, and projects crop up more often, where there's a requirement to reduce the carbon. And in terms of fly-ash and slag, there's been a reduction in the availability of that.

That's all a byproduct of the coal fired power industry. And so there's been a move to look for, How else can we do this? How else can we reduce the carbon? And that's something that's needed in the industry. And MARKHAM is just actively trying to get behind that, to assist making low carbon concrete perform just like the concrete that you are familiar with, the concrete that you're used to.

We need to meet these carbon goals. And how can we evolve, and how can we support that industry as it gets through this change? Because it's always whenever something changes, there will be teething issues. But we do think that at the other side, there's going to be some really good things coming out of it.

And so yes, Hayden, do you want to introduce yourself and talk about fixing some of those mix things as we move through?

HAYDEN:

Cheers. Thank you. Yes, Hayden Prestidge; based out of the Napier office. I work across Australia, New Zealand, but largely now with ready-mix companies. Same through to mining; concrete contractors and some of the soil stabilization contractors.

But a lot of people probably on this chat, and across the country, probably know us purely as being on projects business. And we're doing a lot more with admixtures and products for concrete now. So this is where we are more focused. But yes, that's a good topic. A lot of you would have been using SCMs for a long, long time, and doing them well. And then obviously, like Christine was saying, there's a huge voice out there driving us to pull back on our cement, you know, get some lower-carbon mixes going. And it does present its challenges.

You know, people used to of good old ‘GP cement’, general purpose concrete mixes, and how they behave, how they act, how they set, how they bleed, how they finish, you know, when they can finish them, when they can get their trowels on them. All those things; how they pump, when they can strike formwork; all those sort of things.

And this is really presenting challenges with SCMs. And it's probably ... We see a little bit of a disconnect between authority setting goals around carbon reduction, but then the practicality of the concrete mix, and then what happens at site. There's a little bit of disconnect between, you know, how these new modern mixes perform, and their characteristics. And are we still able to get them the best we can?

So that's really MARKHAM's job right now, is to provide, specialized admixtures that help these same mixes perform the best that can be and really perform like the good old GP mixes. So our whole cause is to make concrete better and drive that. So that's really what we're talking about.

I trust that makes sense, Christine. But it's really... We 100% believe that we can make the sustainable mixes perform like good old GP. And, so it's like sustainability without sacrificing any of what we know of concrete.

CHRISTINE:

Yes cool. Do you want to flick through to the next one, Brendo? And so to that end, MARKHAM really is, as Hayden mentioned, that we’re on the journey with the teams. We are seeing what the expectations are, and seeing, how that works out in reality.

And to the end, we've got Douglas Hamlin - that you're probably familiar with, if you've been on any of our webinars; he's been around MARKHAM for a long time. He's now working full time and research and development, and a lot of that focus is specifically into this type of industry in terms of looking after low-carbon concrete and addressing some of the headaches that we have seen.

There's been targeted solutions to help with early strength gains on low-carbon mixes. Some sites we’re seeing a ‘double bleed’, like a secondary bleed, which was creating delamination issues with some low-carbon slabs. So we're working on admixtures for that. And also, some low-carbon admixtures themselves for workability. But with that workability, not having it run off site, having it workable, but still retaining the slump required to hold that concrete in place; and that early strength gains; helping to hold everything there even though it flows well.

Early set times; durability - so long-term durability as well. So not just here for the next 15, but here for the life of what it's designed for. And the finish and pumpability as well. So creating those admixtures that help that concrete flow and hold in place well. And if you want to take the next one, Haydo? I think we're jumping into real life projects.

HAYDEN:

Yes, I'd be interested if there's any other... these are some of the things we're seeing reasonably consistent across New Zealand, Australia and UK. Obviously we do a little bit of work through there as well; and through Asia. And it's quite a global topic obviously this and I'll just be... Pop it in the chat, if there are other things you’re seeing with the use and increase of cement replacements that's affecting your mix or your projects. We’d be really interested.

But yes, there's some of the things we see. And taking this through to projects now. So obviously there's a lot going on with logistics, warehousing, you know, these ultra-flat floors that we're looking at here on this picture, are becoming more and more common; distribution centres. But even through a lot of data centres or bulk retail. Take the likes of IKEA, you know, those sort of projects.

And this probably goes back to my point where we set goals around reduction of carbon. So, you know, reduce cement in the mix by ‘X’. But then sometimes the placers that are just accepting the concrete out of the truck at the pump, don't know exactly how it's going to behave. And they treat it like they’re used to, and often get a different result. So some of the things we’re seeing - just purely pumping, some of the cement replacements, GGBS or the likes, can provide a stickier mix. We’re talking some trial blends of fly-ash, slag, cement mixes, a little bit different how they behave, how they set up on early strengths. Exactly what Christine was saying, the secondary bleed, how they react; and the pozzalans, and how they let the moisture go, etc.

So finishing can become an issue. And, you know, if that bleed’s still happening underneath, once you form that crust over the top, you know, that can lead to de-lam[ination] things. So really trying to drive that consistency within the mix, make it perform well, hold that moisture, hold that cohesion, rheology together, and being able to do that with some of the admixtures is really helping in that space.

So hopefully that resonates on that one. Do you want to jump into the next one, Christine?

CHRISTINE:

Yes. So let me jump into the precast side of things. So obviously for precast you need that good workability in order to get it to flow well into complex forms. But if it's taking a long time to get up to strength, due to the specific mix, then obviously productivity is dramatically impacted by that.

So, being able to get that formwork off and utilize it again, increases the productivity for the precast yard. And so working towards that. Also in terms of being able to create those complex forms, yes, getting that workability, getting it right to all of the edges; getting that good quality, making sure that it's got that early strength.

HAYDEN:

Yes. That early strength is - and I'll be interested in what others have to say, on this call - the world over, it is the problem with using cement replacements. Obviously it hasn’t quite got the initial kick of cement; and that does behave obviously differently. And precast is a big one for this. Same with formwork contractors on large scale production sites, construction sites.

So same difference. And especially in cold weather. We also know that that is a real challenge, slows it down again. So that's something we've been working on really, really well, I think, and seeing some very good gains. So that one day, 1-3 day strengths, up around sort of 50% gains versus control, and just really kicking in that reaction early. So that makes quite a difference.

And then the next one we probably wanted to talk about was pumping, I'd be interested in any commentary around here as well. But there's obviously pretty much all sites now are pumping, you know, whether it's vertical, up storeys or line pumping or through tunnels, underground, etc. Some of this drive to use... move away from using cement is causing a lot stickier mixes and just not flowing so well, not holding together so well.

And obviously causing some headaches through that process. So being able to introduce some admixtures in there; and these ones are largely hydrogel, colloidal silica based. And helping that flow, because we want it to move... Everyone's probably familiar with the word ‘thixotropic’; so you want it to move under energy well, so that it flows, but as it hits and sets up where you want it to land, you want it to hold and start building up as quick as it can.

So the hydrogel is really good for that. When it's applied under energy, it flows really, really well. Holds it all altogether. The rheology is good. And then starts to work its magic with the hydration of the cement. And getting those strengths going. It's proven well there, through some very good mixes, even some pretty heavy duty like Transport NSW mixes, including fibres, those sorts of things.

And then yes, a lot up into the mining scene with this as well. And it probably ties into shotcrete as well, which Christine, you can have a chat on.

CHRISTINE:

Yes, absolutely. And so, yes. If you want to move slides, Brendo...

BRENDAN:

Yes. I’d just very briefly interrupt to remind everybody to please drop your questions and comments into the chat boxes. And I have left the poll open, but we'll be coming to questions very shortly.

CHRISTINE:

Cool beans! And so yes, in terms of the shotcrete. A lot of that, that Hayden was talking about in the pumping space also moves over to this space as well. So those same benefits where you're getting it to flow well so it sprays, while these admixtures help it to flow through that easily but not be a liquid mess on the other side. So once it hits the wall, it's reducing the bounce-back and sticking in place due to that thixotropic nature. So under energy, flowing. But as soon as it's in place, it holds really well. And then is ready to set up, forming those bonds and getting those early strength gains.

HAYDEN:

Yes, this is a big one. And we do have the mining scene and underground obviously, the tunnels, and shotcreting for protection of earth etc. But they're really interested… Obviously there's a lot of pressure on the industry to drive lower carbon, but can we get this same, you know, 1-3 hour strength set up, so you can layer shotcrete as needed, by using cement replacements. And this is some of the work we're involved with and constantly working on. So it's a really good topic. But also waterproofing, durability into these, you know, bring them back, making sure we're hitting the target of their design life; these sort of things. Protection against... I don’t know, chlorides, acids, whatever we're doing on these sort of structures. And obviously a lot of times shotcrete is used for those sort of projects.

But yes. Keen on questions, answers. When we have the best part of these sessions happen, versus us just talking.

CHRISTINE:

So, yes, I mean, we're speaking from what we've seen and what we've been approached with, but obviously everyone's in different spaces; and so we’re keen to hear something that we haven't covered, something that you've seen, or something that you think there is a gap for.

BRENDAN:

Very good. We had a question coming in the pre-session questions: “Can we make low carbon concrete at the same strength and cost as regular concrete?” [- Daniel]

HAYDEN:

That’s a great...

CHRISTINE:

Or are we making it more costly?

HAYDEN:

Yes it's a really good question. And it's a question on heaps of people's minds to be honest. Short answer is yes, 100%. Whether... The SCMs are probably on par, really, with cement costs at the moment. So there's not too much difference there. And then if you know how to use them, you know what chemicals to put in with them… What sort of admixtures to give them the kick, or getting the workability or durability that they need - it's not a high cost, to be honest. And so you can achieve that quite well.

There's also different admixtures - talking against, cement suppliers here, if you're on the call, sorry. There's also admixtures that will help boost strength, you know, so you potentially could look at different ways of cement reduction, depending on what you're trying to do. I'm not saying for every instance; but you’ve got to hit your strengths.

So it doesn't need to be a higher price, that’s the long and short of it. But there's probably still learning in the industry to do. I think that's the drive that we’re all getting towards, to make them cost-neutral and get it rolling. So yes. Anything I've missed there, Christine? Or any thoughts?

CHRISTINE:

No I think that covered it. Yes. Covered it pretty well. Have we got any more questions yet?

BRENDAN:

Sorry. I just... We covered one that came in from Daniel. Thank you, Daniel. [“So are you able to achieve a mix that is low carbon, with a similar strength and for a similar cost? Or will these low carbon mixes typically be more costly?” – Daniel] I think it's a mirror of the one that came in before the session. So at this stage, no.

HAYDEN:

No, that's good. Yes it's a good drive, because a lot of companies want to jump to this, but that is a big factor. Like, what's it going to do to my cost? What concrete's worth roughly. And can we do it the same? That is another big challenge of moving to SCMs.

BRENDAN:

We’ve got here ... so, “How does MARKHAM provide support in this space?” [- Daniel]

HAYDEN:

Yes, that's good. We're a company that works very closely with specifics of what's trying to be achieved. Say if it's like a shotcreting mix... We are always trying to learn and develop as much as anyone else. So often we'll get involved with trial mix and things. We've got a wealth of technical knowledge we can lean on and share, including data and everything to back claims, that go through if you need to get things past the engineer.

But initially we always like to say, What are you using now? What what are you trying to get to? And then we'll normally run a trial phase. We've got a laboratory here in Napier; and do a lot of trial mixes every day on different things. So either we can incorporate things like that. Otherwise on specific sites, if we're trying to achieve something, see what can be done; whether it's just purely workability or getting into shotcrete or whatever it is and trialling a mix. Providing you some product and playing with it, doing it, working from there.

Whether we need to tweak it or engineer it for something specific. You know, you might say, I need to see a little bit more of this or less of that. And having the ability to play with product and refine it is beneficial. So I suppose that's how we approach that. We do have some of our core products that would slot straight into some of these things. But yea, that would be the guts of how we’d approach that.

CHRISTINE:

Yes. And I think, particularly in this space, all of the mixes are so varied that there isn't a “OK, it fits this. Use this.” It's more of a conversation, specifically. in this SCMs space. So looking at the individual mixes and the individual performance required specific to that mix is really vital. And so, yes, that's one of the main reasons we've got Doug full time looking at all that stuff.

HAYDEN:

Yes. Some of the big projects we've got going on in this space at the moment is benchmarking a lot of early-strength development. We've done a lot in the past with waterproofing and durability. So we’re comfortable what can be achieved there and have a lot of test data on that, it's one thing we might have missed, as well, is that a lot of our approach or all of our approach is liquid admixtures.

So, really easy to integrate into batching plants and standard mixing processes etc, versus powders and labour and those sorts of things as well. So, another question - do you want to take that one, Christine?

CHRISTINE:

I was just going to say one more thing to Daniel, just in case we haven't answered it exactly what you're asking. If I think the best approach to... if you're looking for support in that space is to reach out via email, give us a call.  We'll get the right person onto that. If it's the right space for us, if that's something that we can do. Don't hesitate to reach out; we're happy to walk alongside people as they're exploring in that space for something specific. And then ...

BRENDAN:

“Do MARKHAM admixes help extend service life?” [- Holly]

CHRISTINE:

So, yes, as Hayden mentioned, that’s something that we've been doing for a decent amount of time now. We've got some really good examples in the Aussie mining industry where they've got extremely harsh conditions, both environmentally, temperature-wise, but also the chemicals that they're needing to keep out of the groundwater. And we've got an example there where we’re using the admixture in the concrete. They were previously replacing that concrete pad every 18 months. We're up to six years now without them having to replace that, just due to adding the admixture and the hydrogels in that concrete. So, yes, we've got a reasonable history and a lot of data in terms of extending service life.

HAYDEN:

Yes, probably... Just thinking about that when you were talking of a longstanding one off the track record, that would be into the marine cycle. So we’ve got some very old projects dating back and still holding up very well - literally! - as in, piles in salt water. So that would be a good example of extending that service life, yes.

If you can waterproof concrete, you take away the bulk of corrosion issues, basically. And that's what we’re effectively doing.

CHRISTINE:

Yes.

BRENDAN:

So did you want to put this offer forward, Hayden? I’ll just get this up on the screen. If anybody's faced with a specific project challenge?

HAYDEN:

I’d be really interested in doing that. Everyone’s working through, you know, different things. Some companies are really looking at surface durability of some of their SCM mixes or low-carbon mixes. Some are purely around pumping and placing. Some are purely around bleed. Or there's a lot around early strength, obviously, that we talked about.

But yes, I'd love a discussion of those out there if there's any current challenges you're trying to hit or a process; or if you're thinking, How can I speed up this? Or it might be a methodology on site, you know, we've got to do this. And then the next step is this, if I could save a day here by something, you know, could that help? Obviously we're very much... Our whole message, I suppose, is “making concrete better”. And that's not just the production of concrete, it's everything. It’s the methodology. It's the utilization. So Brendan, you'll send out an email now, right? - that people can respond to?

BRENDAN:

Absolutely. I’ll put both your contact details on that and be glad for anybody's questions and feedback. Very much appreciate it.

Just noticing out of interest in the poll that we put up earlier. Nobody actually put up their hand to say they use SCMs all the time or never. So it's a little bit scattered amongst the industry. But yes.

CHRISTINE:

Let me just see how I can see the results?!

HAYDEN:

I think that's interesting. We were across in UK about 3 or 4 months ago and they've been using slag for a long, long time. So we are probably... I’m not saying New Zealand and Australia haven't been - but not to that level. But we see it coming. We see it coming a lot stronger. And let's get ready for it and let's make it work the best it can.

BRENDAN:

And I think that's it for today. If everybody's said as much as they'd like to! Thank you very much, Hayden and Christine, and thank you very much, everybody for joining us. It's been really good. Appreciate the questions that have come in and hope we can have you on board again next time.

HAYDEN:

Brilliant. Thanks all. Thanks for joining.

BRENDAN:

Thank you.

CHRISTINE:

Thanks everyone. See you!