WEBVTT 00:00.000 --> 00:03.520 The universal construction concrete has been criticized. 00:03.920 --> 00:08.100 It consumes scarce resources such as sand and gravel and thus becomes 00:08.100 --> 00:09.280 increasingly expensive. 00:09.820 --> 00:12.580 Concrete is also climate-damaging, because it releases large amounts 00:12.580 --> 00:14.840 of greenhouse gases not only during production but also during 00:14.840 --> 00:15.940 hardening. 00:19.240 --> 00:23.100 On the other hand, concrete has properties that make it almost 00:23.100 --> 00:24.440 indispensable. 00:25.130 --> 00:27.460 It is difficult to replace concrete in both high- and low-rise 00:27.460 --> 00:27.840 buildings. 00:30.400 --> 00:34.460 Especially the infrastructure, roads, bridges and tunnels, for 00:34.460 --> 00:37.060 example, can only be built with concrete. 00:38.180 --> 00:42.340 Dr. Rebecca Volk is the head of the youth group at the Institute for 00:42.340 --> 00:45.840 Industrial Operations Teaching and Industrial Production of the 00:45.840 --> 00:48.000 Karlsruhe Institute of Technology. 00:48.740 --> 00:54.060 Her and her research team also want to transfer concrete to a closed 00:54.060 --> 00:55.860 cycle of reuse. 00:57.240 --> 01:01.380 The question is how we can manage the value chain of concrete and the 01:01.380 --> 01:04.500 cycle of concrete so well that we can design the whole thing as 01:04.500 --> 01:06.040 environmentally friendly as possible. 01:07.080 --> 01:11.340 It is always the case that you have unplanned input into such material 01:11.340 --> 01:14.480 flows and then have to see how you can extract these unplanned inputs 01:14.480 --> 01:15.120 again. 01:15.660 --> 01:20.200 For example, salt, which is used on the streets and which then simply 01:20.200 --> 01:22.400 causes technical difficulties in the material. 01:23.160 --> 01:25.420 And then you have to think about how to deal with it. 01:25.640 --> 01:28.500 And if you can't deal with it in the recycling process, you have to 01:28.500 --> 01:31.840 drain it and then it's not a completely closed cycle. 01:32.920 --> 01:37.120 But the goal is to get as much of the material in the cycle as 01:37.120 --> 01:37.120 possible. 01:37.120 --> 01:42.340 Dr. Rebecca Volk works as part of the Zero Emission Circular Concrete 01:42.340 --> 01:45.520 project together with colleagues at the Institute for Technical 01:45.520 --> 01:50.380 Chemistry of the KIT and key partners in the construction industry. 01:50.940 --> 01:53.820 There, too, people are increasingly interested in the transfer of 01:53.820 --> 01:59.200 universal construction concrete to a possible closed and emission-free 01:59.200 --> 02:00.800 recycling cycle. 02:00.800 --> 02:06.740 The social pressure continues to rise and the costs for CO2 02:06.740 --> 02:08.000 certificates continue to rise. 02:08.800 --> 02:13.720 The cement plants are also affected by this and then have to think 02:13.720 --> 02:14.660 about how to deal with it. 02:15.080 --> 02:16.920 How can you reduce your CO2 emissions? 02:17.740 --> 02:21.700 And the companies in the industry are very much under pressure and are 02:21.700 --> 02:23.140 working very hard on it. 02:23.140 --> 02:28.020 With the work on the renewal of motorway sections, it is now a 02:28.020 --> 02:29.080 familiar picture. 02:29.660 --> 02:33.800 The concrete is crushed directly on site and then reused in the 02:33.800 --> 02:34.420 substructure. 02:35.940 --> 02:39.820 In the area of high-rise construction, however, the challenges are 02:39.820 --> 02:40.660 much greater. 02:40.920 --> 02:44.940 High-rise construction is much more diverse than a layer of a 02:44.940 --> 02:49.520 motorway, where I have used the same material for kilometers in large 02:49.520 --> 02:51.760 quantities and in an industrial style that can do well. 02:51.760 --> 02:55.360 If you look at the buildings, none of them look like the other. 02:55.620 --> 02:58.300 Both from the outside and from the inside, from the support structure. 02:58.920 --> 03:03.920 There are buildings that are made of brick or limestone walls, 03:04.500 --> 03:08.200 porcelain concrete, and there are steel-concrete construction methods. 03:09.020 --> 03:12.900 And depending on what kind of use was in the building, what kind of 03:12.900 --> 03:18.240 layers came on it, on color, on cleaning, the material is not 03:18.240 --> 03:21.640 available in large quantities in the same material quality when I 03:21.640 --> 03:22.120 demolish the building. 03:23.060 --> 03:26.800 And then I have a mix that I have to deal with first. 03:27.320 --> 03:30.920 Say a steel-concrete building, now let's take an office building, 03:31.140 --> 03:35.640 maybe it had polished walls or painted walls, and this cleaning and 03:35.640 --> 03:39.960 colors, of course, stick to the concrete and pollute the pure 03:39.960 --> 03:40.460 concrete. 03:40.460 --> 03:43.040 In the case of cleaning, for example, it is so that the concrete is 03:43.040 --> 03:46.200 sulfate -soluble and then a recycling is very difficult. 03:46.620 --> 03:52.220 In particular, a reactivation of the cement content in the different 03:52.220 --> 03:56.580 types of steel-concrete is the way to go for the reduction of 03:56.580 --> 03:59.160 greenhouse gases in the use of concrete. 03:59.660 --> 04:03.220 In concrete recycling, there are mainly two different types. 04:03.220 --> 04:07.600 One is that the granule in a concrete is recycled, i.e. 04:07.620 --> 04:08.380 the gravel component. 04:08.380 --> 04:11.820 And the other is that the cement component is recycled. 04:12.220 --> 04:14.160 And that is actually the essential difference. 04:15.040 --> 04:19.600 What is often done now is to recycle this granule, i.e. 04:19.660 --> 04:23.380 simply breaking an old concrete component and using these pieces of 04:23.380 --> 04:25.580 granule again as granule. 04:26.200 --> 04:29.060 What is new is the recycling of the cement component. 04:29.320 --> 04:33.560 And this cement component is then often in this sandy concrete sand, 04:33.840 --> 04:36.840 and that is what is being intensively researched. 04:36.840 --> 04:42.640 A dusty, so-called concrete sand is always created when buildings are 04:42.640 --> 04:43.320 demolished. 04:44.220 --> 04:49.700 Until now, it could not be recycled, but usually ended up in a 04:49.700 --> 04:49.980 landfill. 04:50.480 --> 04:53.040 And here there are different approaches, above all to reactivate this 04:53.040 --> 04:58.520 material via thermal reactivation to a cement. 04:59.160 --> 05:01.680 There are various research projects that are currently running, first 05:01.680 --> 05:06.740 through pure heating, and then a second possibility via a burning 05:06.740 --> 05:08.520 process to produce a belay cement. 05:09.340 --> 05:13.440 Six years ago, the collaboration with the Institute for Technical 05:13.440 --> 05:14.000 Chemistry began. 05:14.440 --> 05:17.380 At that time it was about a concrete component as popular as heavy 05:17.380 --> 05:22.560 recyclable concrete, the so-called pore concrete, also known under the 05:22.560 --> 05:23.920 brand name e-tong. 05:24.760 --> 05:28.900 The pore concrete is an inflated light concrete, I would say, which 05:28.900 --> 05:30.360 has a higher sulfate content. 05:30.360 --> 05:33.340 This is technically a problem, that the concrete does not become so 05:33.340 --> 05:37.540 durable and solid, which is why research and development was 05:37.540 --> 05:37.640 necessary. 05:38.220 --> 05:40.200 And we did that in this project. 05:40.640 --> 05:43.720 And now there is also a follow-up project, where we deal with 05:43.720 --> 05:46.860 concrete, also with various industry partners. 05:47.200 --> 05:50.840 Because KIT researchers have now succeeded in reactivating the cement 05:50.840 --> 05:53.280 component on a laboratory scale. 05:54.060 --> 05:56.900 So for the Rebhaus project, for the pore concrete, we worked together 05:56.900 --> 05:58.420 with the largest manufacturer in Germany. 05:59.200 --> 06:03.600 They make these e-tong stones and at the end of the project they have 06:03.600 --> 06:05.220 fed this old material into their production process. 06:07.740 --> 06:10.800 And there, like with concrete, we only had a kind of granulate and 06:10.800 --> 06:15.300 dust, and we tested various possibilities on how to get the granulate 06:15.300 --> 06:18.800 back into the bricks and the sand. 06:19.600 --> 06:23.280 And we are now doing the same in the urban project for concrete, and 06:23.280 --> 06:24.340 the partner is Holzsim. 06:24.340 --> 06:30.460 We get the demolition material from an industry partner and then it is 06:30.460 --> 06:31.720 prepared, i.e. 06:32.140 --> 06:37.140 ground into different fractions, so that the sieve lines are held in 06:37.140 --> 06:39.060 place by the grating of the material. 06:39.740 --> 06:44.500 And then it is burned in the kiln oven, Belit kiln oven, which was 06:44.500 --> 06:45.420 just opened on Campus Nord. 06:46.440 --> 06:50.180 The reactivation of the cement component in the old concrete also 06:50.180 --> 06:52.380 requires a burning process. 06:52.380 --> 06:56.680 Finding a solution that is as energy-efficient as possible is one of 06:56.680 --> 07:01.100 the big challenges if you want to close the recycling cycle for 07:01.100 --> 07:02.500 concrete to a large extent. 07:03.420 --> 07:07.320 For the first project on pore concrete, we have now examined various 07:07.320 --> 07:10.220 heating possibilities, i.e. 07:10.640 --> 07:13.280 heating with gas and electricity. 07:14.760 --> 07:18.900 If you look at the CO2 balance now, it is better than with 07:18.900 --> 07:20.720 conventional electricity. 07:20.720 --> 07:25.200 We have calculated scenarios with 100% renewable electricity, which 07:25.200 --> 07:25.760 can then be used. 07:26.860 --> 07:29.400 The plants have to allow this, of course, and also the process 07:29.400 --> 07:30.120 temperatures. 07:30.980 --> 07:34.780 So far we are still at about 1000°C process temperature, which has to 07:34.780 --> 07:35.180 be reached. 07:36.980 --> 07:41.800 But that's less than in the primary cement, we're at about 1400°C. 07:42.120 --> 07:45.580 So that's an improvement, and we're still working on lowering this 07:45.580 --> 07:49.760 process temperature in order to have less energy use. 07:49.760 --> 07:53.040 How much CO2 could be saved in this way? 07:54.600 --> 07:55.980 We are also investigating this. 07:56.600 --> 07:59.840 But I can only say this from the pore concrete project at the moment. 08:00.480 --> 08:06.660 You can save up to 0.7 kg of CO2 equivalent per kilogram of old 08:06.660 --> 08:07.620 material. 08:08.660 --> 08:13.620 If you compare it with the current recycling route, and in the case of 08:13.620 --> 08:15.560 pore concrete, this is the deposition. 08:15.560 --> 08:19.880 So there we compared what recycling brings compared to deposition. 08:20.500 --> 08:21.720 And there is a considerable savings. 08:22.380 --> 08:26.800 So the pore concrete is a brick that is very often used in apartment 08:26.800 --> 08:31.180 buildings, one and more family houses, which has wonderful thermal 08:31.180 --> 08:31.840 properties. 08:32.240 --> 08:34.640 So the building loses a lot less energy. 08:35.200 --> 08:40.300 But I can't recycle the material at the moment, but I have to store 08:40.300 --> 08:40.460 it. 08:40.580 --> 08:43.000 This is also due to this sulfate content. 08:43.000 --> 08:49.580 In the new product, we replaced 15% of the input material with old 08:49.580 --> 08:52.980 material and were able to save 13% CO2. 08:54.180 --> 08:56.440 So we were able to save CO2 almost as much as we used old material. 08:58.720 --> 09:01.400 If you want to comply with the consistent quality criteria for 09:01.400 --> 09:05.700 concrete, you can only replace a part of the material with old 09:05.700 --> 09:06.180 concrete. 09:07.080 --> 09:12.240 The expert is still optimistic that the proportion will continue to 09:12.240 --> 09:12.620 increase. 09:13.320 --> 09:14.560 We hope very much. 09:14.600 --> 09:18.420 But it's not just one technology and one recipe, but different 09:18.420 --> 09:19.080 combinations. 09:19.420 --> 09:21.380 On the one hand, how do I collect the material? 09:21.800 --> 09:22.700 How do I prepare it? 09:23.580 --> 09:25.260 What do I do with the stone grain? 09:25.500 --> 09:26.640 What do I do with the sand? 09:27.100 --> 09:29.840 With what energy do I work the electricity? 09:30.320 --> 09:31.900 Or is it just natural gas? 09:32.800 --> 09:35.720 Do I still consider the carbonization at the end of the process? 09:35.720 --> 09:43.280 That means the CO2 is diffused into the material and chemically binds 09:43.280 --> 09:45.340 and hardens the material. 09:46.100 --> 09:49.740 In the meantime, a pilot facility has been built on the campus north 09:49.740 --> 09:50.560 of the KIT. 09:51.700 --> 09:56.120 It will be about how recycling of old concrete can be economically 09:56.120 --> 09:58.020 sustainable on an industrial scale. 10:00.640 --> 10:04.040 We now have the pilot facility where you can make a few kilograms of 10:04.040 --> 10:05.580 this recycled cement. 10:07.340 --> 10:11.440 Of course, this is still far from an industrial use, where several 10:11.440 --> 10:13.400 thousand tons per day run through. 10:14.340 --> 10:20.180 But we are hopeful, because we work with practice partners in all 10:20.180 --> 10:23.040 projects, who are interested in the industrialization of the process. 10:24.400 --> 10:29.740 In the project with Xsella, a part of the old material was put into a 10:29.740 --> 10:31.260 normal production plant. 10:31.260 --> 10:35.720 It was tested on an industrial scale and it worked. 10:36.220 --> 10:41.080 The production of concrete is one of the major causes for industrial 10:41.080 --> 10:42.900 greenhouse gas emissions. 10:43.600 --> 10:47.420 For Dr. Volk, technological advances alone will not be able to solve 10:47.420 --> 10:50.500 the problem of the climate-damaging effects of the construction 10:50.500 --> 10:51.060 sector. 10:52.680 --> 10:55.080 It must, according to her conviction, also be considered in the 10:55.080 --> 10:56.240 direction of sufficiency. 10:57.200 --> 11:02.500 We should simply think about when we need building material, when we 11:02.500 --> 11:05.260 don't need it and what uses we need it for. 11:05.380 --> 11:09.640 We don't necessarily start with recycling and material science, but 11:09.640 --> 11:12.660 before that with the use and what we really need. 11:13.420 --> 11:17.440 We can have the same leverage as in the pure development of technology 11:17.440 --> 11:19.080 of recycling processes. 11:19.360 --> 11:27.040 To think about the living space or office sizes and to use the space 11:27.040 --> 11:31.400 as efficiently as possible or to build smaller and not always bigger. 11:31.980 --> 11:37.080 If you look at the statistics, we have had a demand for square meters 11:37.080 --> 11:38.240 per head of living space for years. 11:38.240 --> 11:41.020 We are currently at 70 square meters per head. 11:41.180 --> 11:42.380 This is constantly increasing. 11:43.060 --> 11:47.140 We should ask ourselves whether this is so much necessary. 11:47.480 --> 11:51.720 The distribution of the whole thing is a social question, because 11:51.720 --> 11:54.360 sometimes the living space is very unevenly distributed. 11:54.880 --> 11:58.500 But we don't use the one we already have very efficiently. 11:58.840 --> 12:02.320 This is simply a discussion that is currently coming to an end. 12:02.660 --> 12:06.120 A lot of attention is being paid to technology development, capture 12:06.120 --> 12:07.140 and storage. 12:08.720 --> 12:13.900 This is also a possibility, but we have many more options of action 12:13.900 --> 12:15.280 that we could talk about.