DFI48 MSSP Expo: BAUER Spezialtiefbau GmbH – Geothermal Activation of Elements Using Bauer's...

Yeah, thank you John for the introduction. Thank you for the opportunity to talk about mixed in place, a totally different product from what we have seen before. It's about the mixed in place technology, which is a soil mixing technology—not a product by itself, but a geotechnical works. But I want to present you how we turn this geotechnical work into a sustainable product, even into a green product, by delivering energy to the building and then it becomes a permanent member.

So here you see just as an introduction about the mixed in place technology, which is a very special type of soil mixing by three continuous flight augers with different flight auger orientations, so that you can make a mixer in the soil, mix in situ the soil with a cement slurry and make it a kind of concrete. This is just an example from a gravel pit, which is a typical application for mixed in place technology—to do the retaining walls, have a base slab, and then you have the temporary works to allow the construction of a building.

In the right you see how we do these continuous walls with the system, just by primary trenches or primary panels, secondary panels, and even additional panels across the joints to make sure that there's a continuous wall without any issues. And by installation of vertical beams you make this wall a structural wall. In the next slide you see on the right a very simple structural system.

So the mixed in place material itself is just the arching material to get the loads from earth and water pressure into the beams, and then the beams are tied back. The beams play a very important role when it comes to making this product a sustainable, permanent product, because we need something to connect the geothermal tubes to. So this is one basic point: we do not change the system, we do not change the retaining wall system. We just use what is necessary for structural use and then we apply a different system.

I think mixing in place or soil mixing is easy to explain. You have the soil already there—in the best case it's kind of a granular material similar to what you use for concrete. Then you have your cement bentonite silos. You need a mixer, of course, to do this cement slurry, and then you pump this cement slurry through the hollow stem of the center or down to the tip, and then you mix in place your material. The result is kind of a concrete—low strength concrete, 8 megapascal, 15 megapascal in that order, whatever you need. You can use less cement and have less strength of course, but this is classical mix design. You just have to accept that you use the soil in place and nothing else.

Visually, you can't really distinguish this soil grout from concrete, just depending on the aggregate you have in there. There's a very short animation where you can see that due to this continuous flight auger, you have a mixing effect over the whole length. So even if you have layers of different soil, you will find each type of soil everywhere—it's a kind of homogenizing process due to the effect of this continuous flight auger. We have a vertical soil transport, but also because it's three augers, you have horizontal mixing, and that's like within the concrete mixing system—you have a very good homogenization of the soil with cement slurry.

The low carbon footprint comes in the next couple of slides. The product mixed in place, or soil mixing, if you have a good soil there, is already a sustainable solution because you do not have many products to get to the site—no transportation. You just have the aggregate already in place, you just add a little bit and disaggregate the soil and restabilize it. It tackles a few of these sustainability topics from the UN agenda—you know these 17 sustainability development goals, where we think at least a few of these you can easily cover with the geotechnical works.

There is a good reason to use mixed in place when you have the right soil, just to avoid additional transports for disposal and transport for concrete. Here you have an in situ mixing method which can be shown in calculations. We have the EFFC carbon calculator—I'm not sure who was in the sustainability group of G12 big. So here you can do these calculations with all the information you need: transports, materials. In typical with these replacement or displacement methods or soil mixing methods, the material part in the CO2 carbon footprint is always a majority. So whenever you can save materials, you will save CO2 emissions with your methodology.

This is an example from a job site in Berlin—Thomas should know this job site from his time in Germany. We have shown with the calculations that you can easily save 55% by replacing methodologies from lots of cement by in situ mixing, and there's also a silicate gel grout slab. So it's two methodologies changed here from the original conventional method. But if you just would only see the wall, which was originally a secant pile wall, then replaced by a soil mixing wall, you can easily show that you can save already 30% of CO2 emissions just by using this mixed in place or soil mixing method, which alone makes it a sustainable product. The EFFC and DFI carbon calculator can be used for these things—it's widely spread already and I think in the future it will be used even more.

The second thing is rather not the global emissions but also the local emissions on a job site. The traffic is very decisive. If you don't have to get away with the disposal of all what you have excavated and transport the concrete into the secant pile wall, you can reduce all these transports to a minimum just by getting the cement to the site, mixing it on site, and then mixing it with the aggregate which is 70% of the volume already. So that means you can save a lot of transports by using applicable methods here.

The geothermal activation itself is quite a short story, but the clue is that you have to prepare yourself and you have to start very early with the process. You have to have the client on board because he needs to decide at a very early stage that he wants to use geothermal energy for his building as an integrated energy system. The story itself is clear: you have the rectangular retaining wall where the geothermal tubes are applied to, and these deliver you the heat from the soil. You can heat your building with this in the winter time, and of course the soil then is cooled down to a certain degree. But in the summertime—and that's kind of a battery reloading effect—you do the opposite. You cool your building in summertime and then you reload the soil or the ground with temperature again.

This is also a design issue—how much you have to manage your building's heat and cooling system so that it's in balance over years. You have to show for authorities, for example, and that's what we do with the numerical modeling usually. There's one extra topic: of course, if you use solar energy, you can even feed more energy into the ground and make even more use of this battery. But what I wanted to show is that we have to show that over many periods you have to make sure that the soil or ground temperature is not changed in a wider perspective. This is a simple graph, but this is the result of a numerical analysis. What you feed in is all the characteristics of your ground and of the use of your building, and then you have to prove once it's installed, and then you can still calibrate your system.

Just a few pictures from the job site. On the left you see just the layout plan, because you have to plan how to get the tubes into the geotechnical works, the H-beams, but also from the connection into the building itself. Here you see just the preparation of these H-beams, these structural beams I showed you earlier. You have to connect these geothermal tubes in the right order according to plan. Then you have your geotechnical works on site, produce your continuous mixed in place retaining wall, and then you install these H-beams which are already applied with these geothermal tubes and with an outlet at a predefined level.

What we have done lately is that we did not only use the retaining wall but also used a base slab of a building, and then it becomes—like it says here, 'Side View Innois concept, time for a new concept.' So even in Germany it's not standard, not regular that we use it. We have a few examples, but it's coming more and more to make use of your ground temperature for geothermal activation. It's actually very simple—you just have to be very early in your planning phase. In this example we have also activated the base slab. Under the concrete slab you install tubes over the whole area, and of course you have to have a layout for that and you may have to interrupt works for 3 days or something like this just to lay out all these tubes. But in the end you save a lot of money for energy supply.

So this is what the layout plan would look like. It's manual work in the end—you really place all these tubes according to this plan. Connect these into the building. There is a watertight system—we call it a tight system—where you connect these tubes through the building, through the base slab, into the base floor, into the cellar of the building.

Not sure if I'm too late already, but that's already my conclusions and the outlook. Mixed in place is already a sustainable solution because you save a lot of CO2—what we call the CO2 footprint is reduced. But then we can add something what we call a handprint, so that it's a sustainable solution we can offer to the client, because it has nothing to do with the geotechnical works. It's just an add-on for the client to make use of this temporary works for a permanent use, for the lifecycle of the building. And that makes—in my eyes, even if I'm very careful with the green thing—this makes it a green product just by activating it geothermally. That's it. If you have more questions, I will be around for a couple of minutes at least before I leave. And we have a booth over there, 411 I think it is. So if you want to know more about the mixed in place technology or other soil mixing technologies, we are happy to help. That's it from my side so far. Thank you.

Actually, we give it over to the client, of course. We do this pressure test and all these things, so until the system is running, then we give it to the house technology guys. But it's the same as if you use geothermal probes—these standard tubes, it's a standard system. You have an enclosed system usually, and the maintenance should be the same as you would have with a classical geothermal probe system. Thank you.