Construction Printing Technology

CONSTRUCTION 2.2020 CPT PRINTING worldwide TECHNOLOGY

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MEDIA PARTNER

GREEN WAY TO 3D PRINT

3D PRINTED CUSTOM BLOCK PAVEMENT AND OBJECTS

INDUSTRIAL CONCRETE PRINTING SOFTWARE

3D PRINTED STAIR MOLDS

2002_cpt_c1-4.indd 1 06.05.20 21:05 3D printed homes page for homeless in Austin Bedroom, bath, kitchen, living room and large porch 60

2002_cpt_c1-4.indd 2 06.05.20 21:05 EDITORIAL

GLOBAL TRENDS AND CREATIVE SOLUTIONS

The whole world is holding its breath while the Corona pandemic is a!ecting our private lives and professional work in a completely unprecedented manner. However, we have no choice but to move on and plan for the future. We need to develop creative solutions in order to avoid further standstill as much as possible. During the past weeks and months, countless trade fairs and technical conferences in the construction sector had to be cancelled, and organizers are all facing the same ques- tion: should the events be postponed to a later date, or cancelled altogether?

In some instances, both of these choices may be unsuitable, and a more innovative approach has to be considered. The organizers of Digital Concrete 2020, which under normal circumstances would have taken place at the beginning of July at Eindhoven University of Technology in the Netherlands, are setting a good example in this regard. This unique event is an absolute highlight for the global construction printing industry and a cancellation is certainly not an option. However, postponing the event to a later date is also close to impossible, considering that the participants would have to travel from all over the world, which at the moment is very di!icult to plan and organize. Consequently, an alternative solution will be implemented, which probably is the only sensible response to the situation: Digital Concrete 2020 will take place as a full online conference.

The organizers simply reverted to modern technology to provide maximum value for their clients and partners. This creative approach is fitting for this cutting-edge technical event, as it perfectly well reflects the developments in 3D construction printing technology. Construction printing is at the forefront of technical innovation, attracts an increasing international attention, and paves the path into the future of construction and manufacturing methods. On all continents, experts are dedicating their professional e!orts to this technology and contribute to the translation of an idea into a global trend. In the current edition of CPT Construction Printing Technology, we report on social housing projects in the USA and the construction of medical facilities in China. We hope that you, dear readers, find inspiration in these projects, which were successfully completed with 3D printing technology.

Without doubt, Contour Cra"ing belongs to the pioneers of concrete printing and we are pleased to present you with a comprehensive account of the company. Also discussed in this edition – a Russian company that is investigating the application of geopolymer concrete in 3D printing. With respect to research and development, we have included interesting technical papers by the Technical University of Dresden and the Danish Technological Institute.

Despite the di!icult circumstances faced by us all, we are pleased to have delivered another edition of CPT Construction Printing Technology that is true to its aim of being at the forefront of the industry. Enjoy reading through the journal and stay healthy!

Any further suggestions? Would you possibly like to publish in CPT? Please feel free to contact me anytime at [email protected] Dipl.-Ing. Mark Küppers, editor in chief

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NEWS 6 Contour Cra!ing Corporation will print 10 3D Concrete printing and other digital four low-income housing units in Los Angeles concrete construction technologies Los Angeles County Development Authority (LACDA) Award 2nd German Industry Seminar, October 28th, 2020, Dresden 8 Additive Manufacturing in Construction (AMC) – 11 Acciona launches global 3D printing center in Dubai The challenge of large scale Culmination of an internal development process DFG funds new CRC/Transregio at TU Braunschweig 11 Unlocking new potential in collaboration with Technical University of Munich New partnership 9 Digital Concrete 2020 12 Exclusively designed furniture Full online conference More than just an eye catcher

RESEARCH & DEVELOPMENT 14 CONPrint3D On-site, large-scale, monolithic 3D concrete printing 23 Towards sustainable 3D Concrete Printing Next Generation 3D-printed Concrete Structures (N3XTCON)

MATERIALS 32 Green Way to 3D Print Geopolymer concrete 37 Partnership to develop printable concrete Specially formulated concrete

DIGITAL PLANNING 38 Industrial concrete printing so!ware Specifically designed to assist research and industry

PRODUCTION & APPLICATION PROJECTS 42 3D concrete printing with an industrial robotic arm 60 3D printed homes for homeless in Austin Next step towards digital project implementation Bedroom, bath, kitchen, living room and large porch 44 3D printed stair molds 64 3D printed isolation houses Reach new design heights Case studies 48 Contour Cra!ing: A revolutionary platform technology 66 Live 3D construction printing of a small house Pioneer of construction 3D printing In front of thousands of visitors 54 3D printed custom block pavement and objects New approach 58 Robots bring the idea from birth to realization 3D printing of buildings and production of non-standard concrete moulds

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CONTOUR CRAFTING CORPORATION WILL PRINT FOUR LOW-INCOME HOUSING UNITS IN LOS ANGELES

Los Angeles County Development Authority (LACDA) Award

In an open competition, proposal solicitation (RFP NO. novative project will showcase the potential of the Contour LACDA19-125) and selection process, the Los Angeles Cra! ing technology in addressing the homelessness problem County Development Authority (LACDA) has awarded in Los Angeles and worldwide. The freedom in the architectur- Contour Cra! ing Corporation (CC Corp) a project on using al design and high degree of customization which is possible construction 3D printing for a" ordable housing. using CC Corp technologies will be utilized to create a livable, sustainable and vibrant community. CC Corp, in collaboration with the design firm HDR and the supportive services provider Volunteers of America Los Ange- In this project, CC Corp’s engineered printing mixture will be les (VOALA) is tasked with building four low-income housing used to print safe and durable houses. Various fresh and hard- units at a designated site in the Los Angeles County. This in- ened properties of the CC Corp’s printing mixtures have been

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tested in order to provide conclusive data and assure the sat- content, and the result is a more sustainable and eco-friendly isfactory performance of the material. This mixture includes construction material. CC Corp is currently investigating the gravel, and therefore it is classified as concrete as opposed to use of supplementary cementitious materials to further re- mortar which is commonly used by many other construction duce the Portland cement content in its engineered printing 3D printing systems. mixture in order to further improve the sustainability of future printed buildings. Use of concrete for building these units is advantageous due to numerous technical, economical, and environmental con- Finally, during this project CC Corp and VOALA will organize siderations. From a technical standpoint, using gravel can im- a job training program. Multiple workshops and hands-on prove the dimensional stability of the hardened material, can training sessions will be held to educate local workers and reduce the risk of cracking in the structure, and can improve vulnerable population on practical aspects of the CC tech- the long-term durability of the printed structure. nology and to engage local workers in di# erent stages of this innovative construction project. From an economical viewpoint, inclusion of large aggregate in CC Corp’s printing mixture has made it possible to reduce the Portland cement content, which is the most expensive in- gredient of cementitious mixtures. Consequently, the cost of CC Corp’s printing material is very similar to the cost of traditional concrete which has been used for decades.

The third advantage of inclusion of large aggregates in Contour Cra! ing Corporation CC Corp’s printing mixture is reduction in the carbon footprint 215 South Douglas Street, El Segundo of the printed units. Production of Portland cement produc- Los Angeles, CA 90245, USA es significant amount of CO". Inclusion of gravel in the print- www.contourcra! ing.com ing mixture makes it possible to reduce the Portland cement

CC Corp, in collaboration with the design firm HDR and the supportive services provider Volunteers of America Los Angeles (VOALA) is tasked with building four low-income housing units at a designated site in the Los Angeles County.

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ADDITIVE MANUFACTURING IN CONSTRUCTION (AMC) – THE CHALLENGE OF LARGE SCALE

DFG funds new CRC/Transregio at Technische Universität Braunschweig in collaboration with Technical University of Munich

Additive Manufacturing (3D printing) is a new manufactur- The basic principles of Additive Manufacturing are based on ing technology that is now introduced in many industrial digitally controlled layer-by-layer component design, without sectors. If the potential of this technology is transferred any mould making or forming processes. “This represents a to the large scale of construction, new design possibilities paradigm shi! to the predominantly manual construction and more e"icient, resource-saving construction meth- techniques, which promote simple element forms and ine#i- ods can be created. The aim of the TRR 277, funded by the cient material utilization,” says the designated spokesperson German Research Foundation (DFG), is to fundamentally Professor Harald Klo! of the Institute of Structural Design at investigate Additive Manufacturing in interdisciplinary re- the TU Braunschweig. Against the background of the enor- search for the implementation into construction industry. mous demand for resources in the construction industry with The DFG is establishing a total of ten new Collaborative its significant contribution to global CO" emissions, this novel Research Centres to strengthen cutting-edge research at technology will provide an e#icient use of material. universities. Starting on 1 January 2020, they will initially receive a total of around 101 million euros in funding for “Great news – for a project in which scientifically outstanding four years. colleagues are working in an exciting field for research,” says

Example of Additive Manufacturing in Construction (AMC) at the Institute of Structural Design (ITE), TU Braunschweig.

Credit: ITE

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Professor Anke Kaysser-Pyzalla, President of the TU Braun- schweig. “I am proud of the team e#ort across the borders of TUM and TU Braunschweig and look forward to further coop- eration on an issue that is highly relevant to society and the economy”.

“I am particularly pleased with the positive assessment of the transregional project,” said Professor Peter Hecker, Vice President for Research and Young Scientists at the TU Braun- schweig. “The SFB/TRR is an award for our research focus ‘City of the Future’ and contributes to raising the profile of civil engineering at the TU Braunschweig”.

The two universities, TU Braunschweig and TUM, have been working together for many years in various fields of engineering disciplines and in particular in the field of Additive Man- ufacturing. Due to the excellent equipment with large-scale research facilities at both locations, a wide variety of mate- Visualization rial-process combinations can be investigated right from the Credit: ITE of TRR277. beginning.

The TRR 277 promotes the future strategic orientation of both Transregional projects (TRR) are a variant of the classical Col- universities. Thus, the CRC/Transregio is integrated into the laborative Research Centres. This enables universities in Ger- research focus City of the Future/Future City at TU Braun- many to closely network and apply for and carry out research schweig and strengthens the action agenda TUM.additives of projects on fundamental issues across all locations. the TUM as part of the “Bavarian Additive Manufacturing Clus- ter”. The TRR 277 aims to contribute to the development of Additive Manufacturing as a key technology for the digitalization of the construction industry, with increased productivity and an e#icient use of resources. Technische Universität Braunschweig Collaborative Research Centres and Transregional Projects Institute of Structural Design (ITE) Prof. Dr.-Ing. Harald Klo! Collaborative Research Centres enable innovative, challeng- Pockelsstraße 4, 38106 Braunschweig, Germany ing and long-term research projects to be carried out in a col- T +49 531 391 3571 laborative e#ort and are thus intended to serve as focal points [email protected] and structures for the applicant universities. ite.tu-braunschweig.de

DIGITAL CONCRETE !"!" Full online conference

Due to the Corona virus outbreak, the Digital Concrete multi-day workshop in Eindhoven will be organized 2020 Organizing Committee, in close coordination with in 2021, focusing particularly on interaction within the RILEM, has decided to reshape the conference in a di"er- Digital Concrete-community. This event will include a PhD ent format. course, an excursion and site-visits, too.

Digital Concrete 2020 will take place as a full online conference, in the same week as originally planned, starting on July 6. Over the course of 4 days, there will be online sessions of approximately 4 hours, including keynote lectures, parallel sessions, Q&A options, and meet & greet facilities. In addition to the online conference, a shorter on-location www.digitalconcrete2020.com

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2_cpt_2002_06-13_News.indd 9 07.05.20 14:05 NEWS #D CONCRETE PRINTING AND OTHER DIGITAL CONCRETE CONSTRUCTION TECHNOLOGIES

2!" German Industry Seminar, October 28#$, 2020, Dresden, Germany

3D concrete printing is particularly suitable both for dig- The seminar o#ers an exhibition options for national and ital construction on-site and manufacturing of concrete international companies active in the field of construction elements in prefabrication. In combination with digital printing which should contribute to intensive exchange be- planning, such new technologies can open up the way tween participants. to Construction Industry 4.0. The digitisation and automation of relevant production processes constitute the The event venue is the Alte Mensa Event Hall (“Dülfersaal“, most promising approach to introducing urgently needed 1&' floor) at the Technische Universität Dresden, Mommsen- changes into the practice of construction. strasse 13/15, D-01069 Dresden. The seminar language will be German. A!er the successful start last year, the 2$% German Industry Seminar on 3D Concrete Printing and Other Digital Concrete Further information: http://tu-dresden.de/bau/3ds2020 Construction Technologies aims to present once again a comprehensive overview of the most important developments, which will be scrutinized critically and impartially. The seminar will take place on October 28th, 2020 at the TU Dresden, Germany. The organizers are the Institute of Construction Materials, the Endowed Chair of Construction Machinery, and Technische Universität Dresden the Institute of Construction Management. Institut für Bausto#e Presentations from industry and science will provide an up- Martina Awassi to-date overview of the state of the art, relevant development 01062 Dresden, Germany trends, but also the challenges in dealing with the new pro- T +49 351 46336311 duction processes. i.bausto#[email protected]

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2_cpt_2002_06-13_News.indd 10 07.05.20 14:05 NEWS ACCIONA LAUNCHES GLOBAL #D PRINTING CENTER IN DUBAI

Culmination of an internal development process

Acciona, a leading company in sustainable infrastructure of cultural heritage made on a real scale using 3D printing on solutions, inaugurated in Dubai a new global 3D printing concrete, the Romanesque arch of San Pedro de las Dueñas, center to meet the growing demand for 3D printed infra- in collaboration with the National Archaeological Museum of structure. Spain (MAN). Acciona has chosen Dubai to install its 3D printing center in The new facilities feature one of the world’s largest operation- order to support the emirate’s commitment to deploying this al 3D printers using powder bed technology. This technology technology in all economic fields and, specifically, in the con- is particularly suitable for generating highly resistant struc- struction sector. tural parts. In addition, the technique uses concrete as base The “Dubai 3D Printing Strategy” is integrated into the material, which renders it an ideal solution for architectural, Emirate’s strategic development plan for cost reduction, pro- urban and building applications. ductivity and performance improvement of products and The printer, with 6x3x2 meters in size, allows greater e#icien- environmental impact mitigation. The Strategy aims to make cy and automation of the construction processes. The 3D Dubai a world-class 3D printing hub. technology o#ers a freedom of architectural and urban de- Among the concrete initiatives included in the Strategy is the sign that had previously been unthinkable. It also opens the introduction of a new law under which 25% of new build- way to scientifically documenting heritage items and making ings’ components must be manufactured with 3D technology replicas from their digital copies, which enables the public to by 2025. contemplate identical reproductions. Acciona’s new production facility is the culmination of an internal development process in the Innovation area starting in 2016, which has enabled the technology to be fine-tuned for commercial use. During this process, Acciona achieved milestones such as one of the first walkways in the world made using 3D printing, in Alcobendas (Madrid, Spain), or the architectural piece www.acciona.com

UNLOCKING NEW POTENTIAL New partnership

IRS Robotics and Vertico are partnering to provide world class 3D concrete printing technology solutions to the Vertico g market. XL 3D Printin www.vertico.xyz As an experienced player in the concrete printing market, Ver- tico has the know-how to provide turn-key, full service concrete printing solutions. IRS Robotics installed a refurbished ABB IRB6640 IRC5 for them on a 6 meter ABB track. Unlocking new potential for the 3D concrete printing market. www.irsrobotics.com

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EXCLUSIVELY DESIGNED FURNITURE More than just an eye catcher

3D concrete provides creative opportunities for architects and planning agencies. The Austrian enterprise 3D Betondruck Solutions has been a pioneer in this innovative technology.

Based on intense development e# orts unique solutions for indoor and outdoor use, such as exclusively designed furniture can be realized. Possible re-use as recycled granulate guarantees sustainability. Di# erent surfaces and colouring of the concrete set individual accents.

www.3dbetondrucksolutions.at

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2_cpt_2002_06-13_News.indd 13 07.05.20 14:05 RESEARCH & DEVELOPMENT

CONPRINT!D On-site, large-scale, monolithic 3D concrete printing

The construction industry faces severe problems resulting from low productivity and increasing shortages of skilled labor. The purposeful digitalization and automation of all relevant stages, from design and planning to the actual construction process appears to be the only feasible solution to master these urgent challenges. Additive concrete construction has a high potential to be a key part of the solution. In the first place, technologies are of interest which would enable large-scale, on-site manufacturing of concrete structures in accordance with the demands of contemporary architectural and structural design. The article at hand presents the CONPrint3D concept for on- site, large-scale, monolithic 3D printing as developed at the TU Dresden. This concept is driven by the demands and boundary conditions of construction practice. It com- plies with common architectural standards, valid design codes, existing concrete classes and typical economic constraints. Furthermore, it targets the use of existing construction machinery to the highest possible extent.

Viktor Mechtcherine, Venkatesh Naidu Nerella, however, making compromises in the geometrical precision Frank Will, Mathias Näther, Jens Otto, Martin Krause, of structural elements to be built. A comprehensive state of TU Dresden, Germany the art can be found in [1], which also provide more details on the technology presented in this article.

The authors started work on the concept of a formwork-free, CONPrint3D concept monolithic construction process using 3D-printing in the Most of the known 3D concrete printing approaches are based framework of the research initiative Zukun"Bau of the on layered extrusion and most of them do not comply with German Federal Institute for Research on Building, Urban the requirement of large-scale, on-site mass construction. A!airs and Spatial Development (BBSR). They named it The main reason is their focus on high spatial resolution, the CONPrint3D®, which stands for large-scale, on-site 3D-print- use of fine filaments, and the concentration on in-plant- rath- ing. The concept was first presented at bauma 2016 (Munich), er than on on-site-fabrication. Apart from high resolution, which is the world’s leading trade fair for construction ma- the use of fine filaments o!ers additional advantages such chinery, and it was granted the ‘Innovation Award’ in the cat- as lightweight printheads, which can be of very simple de- egory ‘research’. The corresponding video and description to sign as well; o"en a circular, vertically oriented nozzle is suf- the concept were published in [2-4], respectively. Since then ficient to provide the necessary control of material flow and the researchers continued to develop this approach further the precision of material placement. However, fine filaments toward its deployment in the practice of construction by also mean both low production rates and the need for very working closely with various industrial stakeholders. fine-grained mortars, which do not comply with existing concrete codes. In contrast, the use of large-size filaments would The CONPrint3D concept should make a time-, labor-, and re- enable high productivity and use of concrete with coarse ag- source-e!icient, advanced construction process possible, but gregates in accordance with valid national and international make the new process economically viable while achieving norms. Since large-scale, on-site mass construction requires broader acceptance from industry practitioners as well. The rather massive cross-sections of simple geometrical shape, main features of the new concept which distinguish it from high spatial resolution is not needed. This does not mean, other approaches are:

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3_cpt_2002_14-31_Research_Development.indd 14 07.05.20 14:48 Figure 1: Fragment of a wall structure 3D-printed using CONPrint3D RESEARCH & DEVELOPMENT technology; two options for application of reinforcement are indicated as well.

Viktor Mechtcherine is Director of Adaptation of concrete-3D-printing to today’s architecture and structural design the Institute for Construction Mate- Other extrusion-based methods are more suitable for producing filigreed elements rials and Professor at the Technis- with more complex geometries, which currently, however, are used relatively rarely. che Universität Dresden, Germany. CONPrint3D is developed for monolithic construction with sharp corners and pre- He is Coordinator of the German Research Foundation (DFG) Priority dominantly straight walls (see Figure 1). Program SPP 2005 „Opus Fluidum Futurum – Rheology of reactive, Maximum use of common construction machinery multiscale, multi-phase construc- At present, concrete printers are expensive special machines. For reasons of econ- tion materials“ and Speaker of the DFG Research Training Group GRK omy and early deployment into the practice of construction, the maximum use of 2250 „Mineral-bonded composites existing construction machinery, with some necessary upgrading, would be of great for enhanced structural impact advantage. CONPrint3D implies upgrading such machines as a mobile concrete safety“. Prof. Mechtcherine is Editor pump for use as a 3D printer, see Figure 2. of the Journals “Cement and Con- crete Composites” and “Materials and Structures”, Member of the Concrete composition and properties of hardened concrete Science Academy of Saxony and within existing concrete standards the Russian Engineering Academy, The development of new standards and their eventual implementation are tedious Chair of RILEM TC RSC-260 „Rec- ommendations for Application of and expensive. Therefore, in the near and medium terms, one should work as far as Super Absorbent Polymers in Con- possible with printable concrete within the existing concrete standards. For CON- crete Construction“ and Member of Print3D, concrete compositions with maximum aggregate size of 8 mm have been the Research Advisory Board of the developed. In addition to ordinary and high-performance concrete, foam concrete German Committee for Reinforced Concrete (DAfStb). He is RILEM [13] and fiber reinforced concrete [8] can be printed. Fellow and awardee of Wason Medal for Materials Research Printheads which enables surface quality and precision / by American Concrete Institute tolerances according to existing standards (ACI) and Innovation Award of the bauma 2016 Munich. At present, printheads are in the main merely simple nozzles. Due to the lack of [email protected] smoothing post-processing, on the one hand a “sausage look” is created which is

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Venkatesh Naidu Nerella is a postdoctoral fellow at Institute of Figure 2: Illustration of CONPrint3D approach depicting a truck-mounted concrete pump as Construction Materials, TU Dres- manipulator for on-site concrete printing. den, where he has been working as research assistant since 2012. He has completed his PhD titled “Development and characterisa- not always acceptable. On the other hand, total control of the material flow as well tion of cement-based materials for extrusion-based 3D-printing” in as the precision of the material placement and its final shape are o"en insu!icient 2019. His main research interests if simple printheads are utilized. Furthermore, the forming of sharp corners and pre- include digital construction, cise openings is problematic. CONPrint3D printheads are designed to deposit large- rheology and numerical modeling. scale filaments of defined geometrical shape and surface quality, while enabling He is a member of RILEM technical committee on “Digital fabrication manufacturing sharp corners as well as accurate endings and openings. with cement-based materials”. [email protected] At the present stage the CONPrint3D concept focuses on replacing masonry walls as a first step. For such applications steel reinforcement is not needed. While the authors have been working on various approaches of introducing reinforcement into the concept (see, e. g., [19-21] and Figure 1), comprehensively presenting this work here would overload this article. Thus, the following deliberations are limited to non-reinforced concrete.

Printer – Manipulator system Most of the known concrete printing projects rely on the use of proven robotics concepts from other industrial applications for moving the printhead. These concepts seem less suitable if they are to be used for large-scale printing of buildings directly on the construction site because there are, in part, completely di!erent conditions:

• rough environment, dirt, weather; Frank Will is holder of the Endowed • frequent assembly and disassembly; Chair of Construction Machinery at • necessity of easy handling for cleaning and maintenance; Dresden Technical University since • required machine mobility for quick changeover between construction sites; 2017. The three major focal topics of the chair are machine automa- • frequently untrained personnel and resulting lack of care in the handling of tion, construction techniques and sensitive technology; drive systems & components. His • conservative attitude of the construction industry to modern technology. professional background is based on a PhD in Mechanical Engineer- ing and 20 years of industrial expe- From the authors’ point of view, it is advisable therefore to search for the concrete rience from di!erent management printing manipulator in the field of existing construction machinery, which have positions in machine and plant been specially developed for this harsh working environment and have proven engineering companies. themselves over many years. The truck-mounted concrete pump is particularly in- [email protected] teresting for concrete printing. On the one hand, it has the needed concrete convey- or technique on board and, on the other hand, it has a long, foldable boom whose range (total lengths of up to 70 m) is large enough to print multi-story buildings. The CONPrint3D process therefore aims to use a truck-mounted concrete pump as a large-scale manipulator for the printhead; see Figure 2.

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Mathias Näther has been working Figure 3: Precision measurements on truck-mounted concrete pump M38-5: as a research assistant at the 1 – target reflector, 2 – printhead dummy, 3 – target-tracking tachymeter. endowed chair of construction machinery at Dresden University of Technology since 2012, where he works on the simulation of com- Several years of research work at the TU Dresden have been concerned with the in- plex technical systems in the field vestigation and modification of the boom drive in order to optimize the positioning of construction machinery and the development of concrete-3D-print- accuracy of these machines. For example, measurements were carried out to deter- ing technology. His work focuses mine the position deviations and mast oscillations of conventional truck-mounted mainly on the development of the concrete pumps; see Figure 4. With the help of this data, optimized drive compo- printhead and handling systems nents, control algorithms, and control systems can now be developed to reduce suitable for construction sites. [email protected] the oscillation amplitudes by up to 95 % and positioning accuracy can be increased [4,5,6].

Printhead for concrete printing Contrary to the described concrete printing approaches that mostly print thin layers of fine-grained concrete, the goal of the CONPrint3D technology from TU Dres- den is to print massive, monolithic wall structures with concrete containing coarse aggregates. This results in more ambitious requirements for the concrete conveyor and the shaping tools of the printhead with regard to delivery rates, robustness and wear resistance. In addition to the requirement of processing concrete with coarse aggregates, the printhead was designed with respect to the following specifica- tions:

• high output of concrete for economical print speeds; • high level of automation; • high level of modularity; Jens Otto is professor of construc- • variable wall cross-sections and smooth wall surfaces; tion management at Dresden • minimal weight; Technical University and heads the institute of construction • easy cleaning and handling. management since 2017. Before returning to the university he was The CONPrint3D method includes the conveying and dosing technology directly working in leading positions in at the printhead; see Figure 4a. This allows better control of the concrete flow. In large construction companies. Due to his experience in construction addition, the fresh concrete properties can be determined and adjusted according process management, Prof. Otto to the requirements directly before printing. A"er further development steps, the has an extensive expertise in the forming system at the concrete outlet will be able to automatically adapt the noz- fields of project management and zle cross-section to the desired layer geometry. Several automatically controlled digital processes for planning and execution. He works in various shaping elements ensure precise shaping of the building-specific wall geometry; committees and is author of see Figure 5. several books and publications. [email protected]

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a) b)

Figure 4: Current printhead for CONPrint3D: a) general view including printhead and laboratory manipulator, and b) detailed view of the base nozzle with a nozzle closure.

The currently most frequently used CONPrint3D printhead is designed to print monolithic wall profiles using concrete with an aggregate size of up to 10 mm. It is capable of printing concrete layers with a cross-section of (width x height =) 150 mm x 50 mm at speeds of up to 10 m/min. During the development of the printhead, special attention was given to a modular design. This allows, for example, the use of di!erent conveying mechanisms or the exchange and optimization of particular components. As indicated above, the printhead can also be equipped with di!erent forming systems adjusted to the respective printing principle:

• Simple outlet nozzles with a fixed cross-section for production of test specimens and wall with unvaried thickness; see Figure 4b; • Complex forming systems with several actuators for printing complex filament shapes and various filament cross-section / wall thicknesses; see e. g. Figure 5; • Alternative forming systems for printing finer, curved structures. Martin Krause has been working as a research assistant at the Institute Through various measurement points, the printhead provides important data for Construction Management since 2014. His research focuses on for understanding and controlling the printing process, especially during the test the economical and managerial phase in the laboratory. aspects of 3D concrete printing. This includes both the analysis of Properties of printable concrete in fresh and hardened states economy and the process-specific boundary conditions as well as Extrudability, buildability, workability and open-time are the key requirements for the optimization of the 3D printing 3D-printable concretes. Printability can be defined as the property of a material strategy. His doctoral thesis on to satisfy these requirements without formation of weak layer-to-layer interface the topic of „Construction process bonds [7]. There are no established process-specific material design approaches optimization of massive concrete wall production by 3D printing“ is and test methods for 3D-printable concrete. Thus, various test methods have been due to be completed this year. developed as part of CONPrint3D research framework, see e. g. [8,9,10] and used for [email protected] designing 3D-printable concretes in a performance-based approach. A comprehensive overview of these methods is provided in [11]. Note that due to the presence of coarse aggregates in concrete, testing of its rheological properties relevant for

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RESEARCH & DEVELOPMENT

www.tu-dresden.de 28th October 2020

1 Dresden, Germany

2 4 3

German Figure 5: Printhead under development: (1) extruder and the complex Industry forming system with (2) nozzle, (3) shaping plates, (4) shutter and several nd actuators for printing filaments with varied cross-section / walls with Seminar varied thickness. 2

3D Concrete Printing 3D-printing becomes even more challenging when compared and other Digital to mortar. Concrete Construction Within the scope and length of the paper at hand, it is not possible to present results for all process-relevant properties for Technologies the newly developed 3D-printable concretes containing coarse aggregates. Thus, only some material parameters will be pre- - STATE OF THE ART sented, and this exemplarily for one printable concrete with maximum aggregate size of 8 mm; see Table 1. - CHALLENGES

Table 1. Composition of printable concrete with maximum aggregate size of 8 mm. - PERSPECTIVES

Con- CEM FA MSS Aggregates [mm] Water SP stituent 0.06- 0-1 0-2 2-8 0.2

Dosage 350 140 105 427 427 325 310 179 5 [kg/m3]

Further information A combination of CEM I 52.5 R Portland cement, micro- can be obtained under silica (MSS) and fly ash (FA) was used as binder. The 3PC had 43.4 % binder paste by volume. The equivalent water-to-cement http://tu-dresden.de/bau/3ds2020 ratio (w/c) was 0.51, calculated in accordance with EN 206-1. eq Very fine quartz sand (0.06-0.2 mm), two natural river sands Technische Universität Dresden (0-1 mm and 0-2 mm) and gravel (2-8 mm), all complying with Institut für Baustoe EN 12620/13139, were used as aggregates. The polycarbox- Martina Awassi ylate-based, high-range water reducing agent was added as 01062 Dresden, Germany superplasticizer (SP). T +49 351 46336311 i.bausto[email protected] 2.20 | 19 The seminar language will be German.

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a) b)

Figure 6: Specimens’ extraction and test setup: a) compression tests and b) bending tests.

The workability of fresh PC was estimated by means of flow Table 2 shows the results of mechanical tests performed on table tests according to EN 12350-5. In view of a spread value the hardened concrete. The compressive strengths of the cast of 36 cm at an age of 20 min, the 3PC at hand can be classified and printed specimens (both for cubes and prisms’ halves) into consistency class F3 (plastic) according to the EN 206-1. are nearly the same, when printed specimens are tested in The extrudability of the composition was proven by printing the parallel case. In contrast, the printed specimens exhibit concrete at various concrete ages up to 90 minutes from wa- about 20 % lower strength values than the cast specimens ter addition using equipment as presented in Figure 4. when tested in the perpendicular case; see Table 2. An expla- nation can be found in [12]. The flexural strengths of printed Extruded layers had right-angled edges with high surface specimens in all cases except Par3, are not significantly di!er- quality; see Figure 4b. Specimens for mechanical tests were ent from cast specimens (below 10 %). The critical case Par3, extracted from several printed little walls. The time interval however, showed the least flexural strength: 66 % lower than between depositions of subsequent layers was 3 minutes. that of the cast prisms. The large size of layers, horizontal lay- The compressive and flexural strengths were measured ac- ing (required for such large filaments) instead of vertical pres- cording to EN 1015-11 on cubical specimens (100 mm x 100 sure-deposition, sti! composition, absence of curing meas- mm) and prismatic specimens (160 mm x 40 mm x 40 mm), ures and smooth nozzle inner surfaces are the suggested respectively, cut out of printed wall elements. In addition, causes for such relatively weak bond. The bond could be sig- compressive strength was measured on prism halves a"er nificantly enhanced and the anisotropy reduced by adequate the flexural tests. To assess possible anisotropy, the speci- preventive measures. This is the subject of ongoing research. mens were tested in various directions with respect to the layer-to-layer interface; see Figure 6. In addition, reference For widespread use of the new technology, a range of printa- specimens were cast and tested to assess the influence of the ble compositions is needed which are suitable for various ap- printing process on the hardened-state properties. All speci- plication scenarios and machine setups. To meet particular mens were tested at an age of 10 days, under consideration of requirements with respect to structural design, construction the anticipated high speed of digital construction. physics and durability, compositions and properties of 3PCs

Table 2. Average strength values of the 3D-printable coarse aggregate concrete at an age of 10 days (in MPa; standard deviations are given in parenthesis).

Cast Printed cubes Printed prisms

Test C-Cubes C-Prisms PerpC ParC Perp1 Par1 Perp2 Par2 Par3

57.7 57.3 46.9 58.2 46.8 57.5 48.6 54.7 53.3 Compression (1.2) (2.9) (1.0) (1.8) (3.3) (2.9) (4.4) (2.5) (2.6) 7.41 6.70 6.72 6.75 7.45 2.52 Flexure X X (0.25) (0.29) (0.37) (0.37) (0.45) (0.93)

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should be versatile. Currently this translates into 3PCs with 1,9 m#/h taking into account some delays for wall connec- aggregate sizes ranging from 2 mm to 16 mm and compres- tions [16]. Two workers are scheduled for the printing pro- sive strengths from 1 MPa (foam concrete) to 80 MPa. For ex- cess: A specially trained machine operator and a professional ample, in the project CONPrint3D Ultralight, the authors de- skilled worker. Further information to economic prospects of veloped a series of load-bearing, lightweight printable foam 3D concrete printing can be found in [16]. concrete with densities ranging from 600 kg/m3 to 1500 kg/m3 and compressive strengths from 1 to 10 MPa [13]. Reduction Compared to conventional construction methods, the num- of carbon footprint and sustainable construction are a cru- ber of qualified skilled workers is significantly reduced. On cial requirement for the seminal construction materials and the one hand, this has a positive e!ect on the construction processes. While the concretes developed for CONPrint3D costs. On the other hand, in Central Europe the trend is be- applications have lower cement content in comparison to the ing recognized that fewer and fewer workers are available most known examples of printable concrete, see Table 1, fur- for skilled manual labor. In less developed countries, there ther reduction of clinker content in 3PCs is targeted in ongo- is usually enough a!ordable labor. But o"en the workers are ing research using limestone calcined clay cements and novel not su!iciently qualified to build high-quality concrete struc- binder systems. tures.

Economic feasibility, market potential and data management To be able to produce building structures autonomously with Concrete work is still considered to be labor-intensive and concrete 3D-printing, the demanding boundary conditions time-consuming. In particular, the formwork significant- of the construction processes must be mastered by the ma- ly determines the execution time and take at about 25 % to chine. For this purpose, the construction machine must be 35 % a high proportion of the total cost of the structural work, controlled by means of specially prepared data structures even for relatively simple geometrical configurations. There is and sophisticated data management. The basis is a Build- consensus in science that the introduction of additive manu- ing Information Model (BIM) containing geometric and ma- facturing in construction has significant economic potential terial-specific information. The digital structure required for [3,14,15]. the concrete 3D printing process has to be extracted from the BIM model, then sliced, and a"er that converted into a An essential criterion for a successful market launch of CON- machine-readable G-Code. Therefore, an integrated digital Print3D® is the economic competitiveness with convention- process chain must be developed. This topic is addressed in al construction methods. The aim of the first development detail in [17,18]. step is the automated production of unreinforced concrete walls, continuously and reliably, in order to replace manual Summary and outlook masonry construction. With 75 % of the total construction The article at hand elaborated the necessity of developing volume, traditional masonry construction is still the most digitized, fully automatic technology for large-scale concrete commonly used method in residential constructions in Ger- construction. Against this background the authors presented many. The building materials bricks (about 32 %), sand-lime their concept CONPrint3D for on-site, monolithic 3D-printing. bricks (about 17 %), cellular concrete (22 %) and lightweight The concept is based on layered extrusion as the most exist- concrete (4 %) are used in residential construction [15]. This ent approaches. The main features of the new concept which already illustrates the high market potential in Germany only. distinguish it from other approaches are: In addition, the process can be certified as highly competitive worldwide for buildings up to five stories. In particular, poten- • adaptation of concrete-3D-printing to today’s architecture tials are seen also in the emerging economies, where there and structural design (sharp corners, straight-line geome- is a high demand for simple, solid constructions. In a second tries, wide monolithic cross-sections); development step, reinforced concrete components are to be • maximum use of the common construction machinery, produced in order to expand the application scenarios suc- such as truck-mounted concrete pumps; cessively. In a third development step finally installations of • concrete composition and properties of hardened thermal insulation and technical building equipment, such as concrete within the existing concrete standards; electricity, water and sewage are to be integrated. • printhead which enables surface quality and precision according to existing standards. In economic feasibility studies, the execution time and construction costs of CONPrint3D were investigated. Using the While introducing CONPrint3D, various perspectives were example of one floor of a detached house, a comparison presented, namely those of mechanical engineering, con- was made between CONPrint3D and conventional masonry crete technology, and construction management. At the construction. As a result, cost savings potential of 25 % and present stage the main challenge in applying truck-mounted four to six times shorter execution times were estimated. concrete pumps as on-site 3D-printer is the insu!icient posi- The wall-printing of a floor with a space of approximately tioning accuracy of the printhead. Currently optimized drive 130 m2 can be realized in about one day [15]. The currently components as well as measurement and control systems are conceivable printing speed is 150 mm/s with layer heights of being implemented to considerably improve the movement 50 mm. This enables a printing performance of approximately precision of the pump mast.

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Concrete compositions for large-size filament printing were Acknowledgements developed. While the mechanical performance of the print- Authors express their sincere gratitude to the German Federal ed specimens was nearly identical to that of the cast speci- Ministry for the Environment, Nature Conservation, Building mens made of the same concrete mixture, testing of the print- and Nuclear Safety (BMUB) for funding the preceding re- ed concrete in various directions yielded a certain extent of search projects through the research initiative Zukun" Bau of anisotropy resulting primarily from the quality of the interlay- the Federal Institute for Research on Building, Urban A!airs er bond. Another challenge the authors deal with is enhanc- and Spatial Development (BBSR). Furthermore, the financial ing robustness of the mixtures specifically with respect to support of the German-Czech project digiCON$ - Digital Con- on-site applications. crete Construction by the Federal Ministry of Education and Research (BMBF) is highly acknowledged. We also thank our In its present form, CONPrint3D technology is designed as an industrial partners: OPTERRA Zement GmbH (Werk Karsdorf), alternative to manual erection of masonry walls. The market MC-Bauchemie Müller GmbH & Co. KG, BAM Deutschland AG shares and economic viability of this alternative have been (Dresden branch), KNIELE GmbH, Cervenka Consulting and explained. The use of large-size filaments for printing massive CERION GmbH. walls requires particular printing strategies and purposeful adaptation of the data from digital planning.

References [11] V. Mechtcherine, V. Nerella: Fresh state requirements to 3D-printable [1] V. Mechtcherine, V.N. Nerella, F. Will, M. Näther, J. Otto, M. Krause: cement-based materials. Construction Printing Technology 1 (2020) Large-scale digital concrete construction – CONPrint3D concept for 10–17. on-site, monolithic 3D-printing. Automation in Construction 107 (2019) [12] V.N. Nerella, S. Hempel, V. Mechtcherine: E!ects of layer-interface 102933. properties on mechanical performance of concrete elements produced [2] CONPrint3D: 3D-Druck mit Beton - YouTube, Technische Universität by extrusion-based 3D-printing. Construction and Building Materials Dresden (2016). https://www.youtube.com/watch?v=EhNGgY42e- 205 (2019) 586–601. qY&t=16s (accessed April 26, 2019). [13] V. Mechtcherine, V. Markin, F. Will, M. Näther, J. Otto, M. Krause, V.N. [3] V.N. Nerella, M. Krause, M. Näther, V. Mechtcherine: 3D-Druck-Techno- Nerella, C. Schröfl: CONPrint3D Ultralight - Herstellung monolithischer, logie für die Baustelle - Interdisziplinäres Forschungsprojekt der TU tragender, wärmedämmender Wandkonstruktionen durch additive Dresden. Concrete Plant International / BetonWerk International 4 Fertigung mit Schaumbeton. Bauingenieur 94(11) (2019) 405–415. (2016) 36–41. [14] G. De Schutter, K. Lesage, V. Mechtcherine, V.N. Nerella, G. Habert, [4] M. Näther, V.N. Nerella, M. Krause, G. Kunze, V. Mechtcherine, I. Agusti-Juan, Vision of 3D printing with concrete — Technical, R. Schach: Beton-3D-Druck Machbarkeitsuntersuchungen zu kontinu- economic and environmental potentials. Cement and Concrete ierlichen und schalungsfreien Bauverfahren durch 3D-Formung von Research 112 (2018) 25–36. Frischbeton. Projektbericht (AZ: SWD-10.08.18.7-14.07) Dresden, 2016. [15] R. Schach, M. Krause, M. Näther, V.N. Nerella, CONPrint3D: 3D-Concre- ISBN 978-3-7388-0028-9. te-Printing as an Alternative for Masonry. Bauingenieur 92 (5) (2017) [5] S. Zorn: Regelungstechnische Stabilisierung mehrgliedriger Ausleger 355–363. am Beispiel der Autobetonpumpe. ATZ O!highway 03 (2018) 46–51. [16] J. Otto, J. Kortmann, M. Krause: Wirtscha"liche Perspektiven von Be- [6] S. Zorn, F. Will, P. Mögle: Control stabilization of multilink manipula- ton-3D-Druckverfahren. Beton- und Stahlbetonbau 115 (2020) He" 5. tors in a truck-mounted concrete boom pump. ATZheavy duty world- doi:10.1002/best.201900087. wide 3 (2018) 44–49. [17] M. Krause, J. Otto, 3D-Concrete-Printing: Digital data flow with BIM. [7] V. Mechtcherine, F. P. Bos, A. Perrot, W. R. Leal da Silva, V.N. Nerella, Bauingenieur 94 (5) (2019) 171–178. S. Fataei, R. J. M. Wolfs, M. Sonebi, N. Roussel: Extrusion-based [18] M. Krause, J. Otto, A. Bulgakov, D. Sayfeddine: Strategic optimization additive manufacturing with cement-based materials – of 3D concrete printing using the method of CONPrint3D. Production steps, processes, and their underlying physics: In: Proceedings of the 35th ISARC, IAARC, Berlin, 2018 1-7. A review. Cement and Concrete Research 132 (2020) 106037. DOI: 10.22260/ISARC2018/0002. [8] V.N. Nerella, M. Näther, A. Iqbal, M. Butler, V. Mechtcherine: Inline [19] H. Ogura, V.N. Nerella, V. Mechtcherine: Developing and testing of quantification of extrudability of cementitious materials for digital strain-hardening cement-based composites (SHCC) in the context construction. Cement and Concrete Composites 95 (2019) 260–270. of 3D-printing. Materials 11 (2018) 1375. [9] V. Mechtcherine, V.N. Nerella, K. Kasten: Testing pumpability of concre- [20] V. Mechtcherine, J. Grafe, V.N. Nerella, E. Spaniol, M. Hertel, U. Füssel: te using Sliding Pipe Rheometer. Construction and Building Materials 3D-printed steel reinforcement for digital concrete construction – 53 (2014) 312–323. Manufacture, mechanical properties and bond behavior. [10] V.N. Nerella, M.A.B. Beigh, S. Fataei, V. Mechtcherine: Strain-based Construction and Building Materials 179 (2018) 125–137 approach for measuring structural build-up of cement pastes in the [21] V. Mechtcherine, V.N. Nerella: Integration der Bewehrung beim context of digital construction. Cement and Concrete Research 115 3D-Druck mit Beton. Beton- und Stahlbetonbau 113 (2018) 496–504. (2019) 530–544.

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TOWARDS SUSTAINABLE !D CONCRETE PRINTING

Next Generation 3D-printed Concrete Structures (N3XTCON)

The number of extrusion-based 3D Concrete Printing The N3XTCON project aims at developing technologies that (3DCP) applications has increased rapidly over the past bring 3D Concrete Printing (3DCP) to an industrial scale – with few years. This indicates an industrial strive to explore a clear focus on sustainability and new architectural designs. new construction methods, aiming at boosting productiv- Its scope includes both on-site and prefabrication applica- ity and obtaining new architectural designs; thus, shi!ing tions based on extrusion-based 3DCP, including the produc- building methods into a manufacturing process. To ena- tion of large-scale reinforced concrete structures as well as ble that, it is necessary to create a seamless link between residential buildings. The project is funded by the Innovation design, materials, and processes in construction. This Fund Denmark and runs until 2022. calls for research on material development, process monitoring, and material characterisation methods [1]. To ad- The developments covered in the project range from material dress such need, while generating new knowledge to the characterisation to numerical modelling and process control construction industry, the Danish Technological Institute as illustrated in the diagram shown in Figure 1. Whereas Fig- – in collaboration with key players from the Danish con- ure 2 depicts some of the initial project results; specifically: struction industry – started the project “Next Generation a Finite Element Model describing the failure of printed ele- 3D-printed Concrete Structures” (N3XTCON). ments, a Computational Fluid Dynamics model describing the shape of extruded layers depending on 3DCP process parameters, and a Digital Image Correlation (DIC) characterisation method used to monitor layer deformation on printed Wilson Ricardo Leal da Silva, Danish Technological Institute, Denmark elements. Sergio Ferreiro Garzón, Cementir Holding N.V., Italy Thomas Juul Andersen, Danish Technological Institute, Denmark In this publication, we present the results of a N3XTCON case Ingrid Ahrenkilde, Cementir Holding N.V., Italy study related to the fabrication of a concrete column using a novel cement type developed by Cementir Holding N.V. and

Figure 1: Development steps covered in the N3XTCON project.

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Wilson R. Leal da Silva, PhD is a Product Manager at the Danish Technological Institute. His fields of interests include cement and concrete technology; in particular, mix design and testing of Ready- mix concrete, self-compacting concrete, high-performance concrete, and mass concrete. His experience results from activities developed in Brazil, Czech Re- public, Denmark, Germany, and Switzer- land. At present, he works on R&D project within 3D Concrete Printing and machine learning applied to concrete inspection. In addition, he is heavily engaged on the Figure 2: A snapshot of the initial developments within the N3XTCON project. (Courtesy of the dissemination of knowledge to the N3XTCON project partner Technical University of Denmark; R. Comminal [2] and S. Andersen [3]) 3D Concrete Printing industry. [email protected] an in-line mixing nozzle that is currently under development at the Danish Tech- nological Institute. Through this case study, we cover the key aspects in the design-to-fabrication workflow; namely, architectural design, material development, 3DCP process setup, and fabrication of a concrete element.

Design to fabrication – case study

Architectural design Extrusion-based 3DCP has revealed new architectural design opportunities that di!er significantly from what is possible with the use of formworks. Some of these opportunities have been explored in the design and fabrication of a column. Specif- ically, one characteristic enabled by 3DCP is the possibility to make freeform cavities that normally would encapsulate or lock the formwork inside the concrete, i.e. It is not likely possible to remove the formwork in one piece a"er casting.

Sergio Ferreiro Garzón, PhD is a Research Designing with freeform cavities gives new expressions to concrete structures and Specialist working at the department of R&D, Quality and Technical Sales Support – together with the characteristic layered surface resulting from extrusion-based of Cementir Holding N.V. His fields of 3DCP – adds a design language that refers to the digital fabrication method. In other interests include cement chemistry, words, the surface and geometrical features of the concrete element become the concrete technology and durability; in “fingerprint” of the digital fabrication method used to produce such element. In ad- particular, development of new technologies for cement and concrete production dition, this fabrication approach enables an optimized and reduced material con- with low embodied CO2 emissions by the sumption and, thereby, a more sustainable approach avoiding unnecessary bulk use of optimum combinations of highly volumes. reactive supplementary cementitious materials. His experience results from activities developed in Spain and Denmark. The so-called “twisted column” in the case study featured in this article results At present, he works on R&D projects from a parametrically designed geometry using a combination of the 3D-modelling within Green transformation of the typi- so"ware Rhinoceros and the visual programming plugin Grasshopper. The design cal construction materials industries and, originates from a baseline curve that gives the base cross-section of the column more recently, 3D Concrete Printing. Also, he is heavily engaged on the – including free-form cavities. The baseline curve was then rotated 2 degrees per dissemination of knowledge to the each printed layer, ending up in a 360 degrees twist at 180 layers. The combination cement and concrete industries as of the gradual rotation and shape of the baseline curve results in a design where well as academia. the geometry varies the expression of the elevation from top to bottom. In addition, [email protected] the rotation pushes the limits of the material properties by introducing a twisted

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Thomas Juul Andersen is educated archi- tect with focus on sustainability, energy and the architectural opportunities of concrete – both in terms of concrete structures, geometries, and surface textures. He is one of the developers behind The High-Tech Concrete Laboratory at the Danish Technological Institute, and has over 10 years experience in the development of digital fabrication processes for the production of formwork for non-standard concrete structures and 4 years of experience in development Figure 3: Twisted column geometry and printed section (in red). of 3D concrete printing technology. He has been among the lead developers in several research and development projects in this working field. cantilever towards the inner hollow of the column. The final geometry of the “twist- [email protected] ed column” as well as the section that has been printed are shown in Figure 3.

Material development From a material outlook, extrusion-based 3DCP requires fine control of the concrete structural build up – ranging from a material that is initially fluid to a sti! material as the printing process evolves. At first, the material needs to maintain its workability to enable pumping. Next, it must sustain its shape a"er extrusion and then exhibit enough structural build-up to prevent collapse. The latter relates to a characteristic referred to as buildability.

The so-called material buildability is strongly related to its early-age structural build- up. Figure 4 depicts the required structural build-up a"er extrusion and the failure mechanism of printed elements suggested in [4]. A thorough review of the mechanisms responsible for structural build-up can be found in [5]; while [6] o!ers a comprehensive overview of the underlying physics relevant to extrusion-based 3DCP. Ingrid Ahrenkilde is working as Manager of Research & Quality Centre, Aalborg at Cementir N.V., where her main function is within cement, raw-materials, SCM and concrete technology / applications, including R&D projects and consulting activities. In addition, she provides expert knowledged to Cementir N.V.‘s cement and concrete activities in Denmark and globally, while assisting Cementir N.V in market introduction of new products. Her experience results from more than 25 years in the construction industry covering Precast, Ready-Mix and Admixture production. [email protected]

Figure 4: Required yield stress (τd) / elastic modulus (Ed) and di!erent 3DCP failure mechanisms.

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Concrete’s structural build-up can be tuned in many ways, In addition to enabling a proper structural build up using e.g. with viscosity modifying agents and shotcrete accelera- CAC, there exists costs and sustainability aspects to be con- tors. The former fails to provide enough strength at very-early sidered in the development of 3DCP mix when compared to age, so printed elements cannot be moved shortly a"er print- conventional concrete compositions. A"er all, in most cases, ing; whereas the latter has a rather fast e!ect, thus hindering custom-designed 3DCP mixes comprise high cement content. operation. Conversely, blended binder systems, e.g. a blend To overcome that, the first alternative is to replace the most of Ordinary Portland Cement (OPC), Calcium Aluminate Ce- used white or grey CEM I (that comprise clinker content from

ment (CAC), and Calcium Sulphate (C$), o!er a more promis- 95% up to 100% and with overall CO2 emissions ranging from

ing and robust alternative, since CAC combined with C$ can 860 to 1235 kg CO2/t cement, respectively [7]) with blended modulate the system’s structuration and reactivity; in other binder systems comprised of CEM I and supplementary ce- words, it can control both sti!ening during the printing phase mentitious materials, e.g. fly ash and limestone filler. and hardening post printing. The structural build-up scenarios provided by using blended binder systems in combination Another most recent alternative is the FutureCEM, i.e. a CEM with hydration retarding admixtures are shown in Figure 5. II/B-M(Q-LL) 52,5 N cement with a low clinker content, where clinker is replaced with a blend of calcined clay and limestone The activation strategy Type C (Figure 5) is the one adopted filler. This Portland-composite cement has been gaining in the study presented in this article. Specifically, a CAC slur- momentum in the cement industry due to a combination of ry is used as the triggering agent in retarded mortars (OPC- factors such as fly ash shortage in some markets, e.g. in Den- based) via a delayed slurry addition in a custom-designed in- mark, as well as raised concerns on the sustainability aspects line mixing nozzle. Details on the nozzle as well as dosing and of cement and concrete production. mixing systems are described along with the 3DCP setup in the following section. FutureCEM was under development at Cementir Holding N.V as a result of the SCM and Green Concrete II projects [8,9]. The composition figures related to one of the FutureCEM batches produced at industrial scale trials is summarized in Table 1. These values are presented along with the equivalent values for a White CEM I – also used for 3DCP in previous experiments at the Danish Technological Institute.

Note that the Environmental Product Declaration (EPD) of FutureCEM is currently under development, but an approxi-

mate estimation is that the CO2 emission of this cement will

be around 600 kg CO2/t cement. Thus, a change in the main

binder constituent alone features ca. 30% reduction in CO2

emission in contrast to CEM I 52.5N (LA) (ca. 860kg CO2/t cement [10]) and ca. 45% as compared to White CEM I 52,5 R SR5

(ca. 1100kg CO2/t cement [11]).

To access the feasibility of using FutureCEM for 3DCP, while keeping the same structural build-up activation strategy, i.e. CAC slurries injected and mixed in the nozzle, we utilized nee- dle penetration tests. Such test allows for accessing the evolu- Figure 5: Control of structural build-up with blended-binder systems. tion of yield stress – computed based on the penetration load

Table 1: Main cement performance parameters and composition requirements.

White EN 197-1 FutureCEM EN 197-1 Parameter CEM I 52,5 R SR5 requirements CEM II/B-M(Q-LL) 52,5 N requirements Clinker content (%) 100 95-100 69 65 -79 Calcined clay & limestone – – 31 21 - 35 contents (%)

fc, 2d (MPa) 44 ≥ 30 28 ≥ 20

fc, 28d (MPa) 72 ≥ 52.5 61 ≥ 52.5 Initial setting time (min) 145 ≥ 45 155 ≥ 45 Density (kg/m3) 3130 – 3000 –

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Figure 6: 3DCP element printed with White CEM I-based mortar and Figure 7: Evolution of yield stress since activation using CAC slurry 10% CAC bwoc at a vertical build-up rate set at 1.67m/h. (White CEM I vs FutureCEM).

over time as suggested in [12]. Note that, in order to capture at a vertical build up rate of 1.67 m/h – one example is depict- the evolution of yield stress from the first minutes of activa- ed in Figure 6. This mix comprises White CEM I (CEM I 52,5 R tion up until one hour, we utilized an adapted penetration tip; SR5), limestone filler, fine sand (> 0.5mm), water, and a hydra- specifically, a hemispherical tip with radius equal to 10mm. tion retarder dosage of 0.50% bwoc to maintain a long open time during printing. At this stage, the analysis of results was rather straightforward, i.e. we carried out penetration tests to access whether a Moreover, the mix has a water-to-binder ratio of 0.39, 0.10% of mix comprising FutureCEM activated with 10% CAC by weight PCE-based plasticizer, and 0.10% of viscosity modifying agent of cement (bwoc) would exhibit the same structural build up bwoc. In the tested mix, we replaced the equivalent volume behavior as the one comprising White CEM I and activated of White CEM I with FutureCEM. The obtained evolution of with the same CAC dosage. The latter corresponds to a mix yield stress for White CEM I and FutureCEM mixes, including a design that has been successfully used in our 3DCP setup [13] FutureCEM-based mix without CAC, is shown in Figure 7.

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Dosing pump In-line mixing nozzle (prototype 1.0)

Figure 8: 3DCP setup at the Danish Technological Institute.

Mortar pump

The results in Figure 7 show that the FutureCEM base mix clinker content in CEM I and FutureCEM di! ers. In particular, (without CAC) exhibited a steady yield stress value during FutureCEM has a greater CAC dosage by weight of clinker the monitoring period, i.e. the retarded base mix will remain (bwok) when compared to White CEM I. The actual dosages workable during the printing time. Next, when comparing are 10% CAC bwoc and 10.5% CAC bwok for the White CEM I the results of the CAC-activated systems, we observed a good mix, and 10% bwoc and 13.1% bwok for the FutureCEM mix. match in the yield stress evolution. In order words, the Future- CEM-based mix is expected to be buildable (without collapse) 3D Concrete printing setup at the same vertical build-up rate tested in previous studies The 3DCP installations from the High-Tech Concrete Lab at with the CEM I-based mix, e.g. in [13]. Note that the equiva- The Danish Technological Institute served as basis for the lent dosage of CAC in both systems is not the same, since the printing experiments. An overview of the 3DCP setup is shown in Figure 8. Basically, the setup comprises a 6-axis industrial robot (Fanuc R-2000iC/165F), two progressive cavity pumps (NETZSCH) equipped with a frequency inverter. The first pump, namely “mortar pump”, is used to pump the mortar at flow rate up to 100 dm3/h; whereas the second, namely “dos- Watch video about printing test under the ing pump”, pumps the activating slurry at a flow rate up to 3.6 3 N3XTCON project. dm /h. The flow ratio between these pumps depends on the slurry dosage and solid-content set in the mix design as well as printing process parameters.

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Figure 9: Initial results on the homogenization between 3DCP mortar and CAC slurry a"er extrusion using the in-line mixing nozzle.

In addition, the setup includes a 3.0m long steel-wire rubber mixing nozzle, without necessarily leading to conclusions hose (Ø32mm), and a custom-designed round nozzle with on whether the current configuration is optimal. To evaluate Ø20mm equipped with a mixing sha" developed at the Dan- that, complementary studies on mixing quality, residence ish Technological Institute. The latter is Ø32mm and 200mm time, and washout function of the in-line mixing nozzle are to long sha" that is equipped with mixing blades controlled by be performed in the N3XTCON project. a motor. In this sha", the base mortar is continuously mixed with the CAC slurry at a given volumetric ratio and mixing Prior to any printing task, the pump hopper, hose, and ex- speed. trusion nozzle were primed with a thin limestone filler paste. Also, a pneumatic vibrator was attached to the hopper of the For the printing process parameters used in our case study, “mortar pump” to ease concrete pumping, since agitation re- the residence time of the material in the mixing sha" is 10.2s duces the internal particle friction and, thus, lowers the e!ec- (i.e. mixing sha" volume / mortar flow rate). Such short resi- tive viscosity of the material. Also, an impeller was added to dence time proved enough to activate the White OPC-based the hopper of the “dosing pump” to prevent any slurry segre- mortar using a CAC slurry and black pigment. The scenario, gation during the process. resulting from an empirical study in our 3DCP setup, is shown in Figure 9. This figure depicts the result obtained from var- Finally, the design-to-production framework is based on ying several parameters, e.g. mixing energy as well as flow a custom algorithm developed in Rhino and Grasshopper. rates of the mortar and dosing pumps. As such, Figure 9 is This algorithm translates toolpath designs in to GCode files, merely presented to illustrate the outcome of the in-line i.e. point coordinates and associated orientation vectors

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Figure 10: The “Twisted Column”.

required for the robot end-e!ector to follow a spec- Table 2: 3DCP process parameters for the “twisted column” fabrication. ified path. The generated files are then sent to the robot via RoboDK®, which computes the toolpath Print speed [mm/s] 50.0 through inverse-kinematics. Layer height [mm] 10.0 Fabrication of the “twisted column” Contour length [m/layer] 1.29 For the “twisted column” fabrication, we prepared Vertical build rate [m/h] 1.39 45 dm3 of the base mortar and 2.5 dm3 of the CAC Time per layer [s] 25.8 slurry. These two components were processed in 3 our 3DCP setup based on the process parameters Mortar pump flow rate [dm /min] 0.95 listed in Table 2. Dosing pump flow rate [ml/min] 56.2

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In total, 72 layers were printed – the printed element is de- Acknowledgements picted in Figure 10 at di!erent time steps. While this repre- The authors would like to acknowledge the support of the In- sents about half of the height the original geometry (Figure novation Fund Denmark (Grant no. 8055-00030B: Next Gener- 3), the obtained results prove the main aspects considered in ation of 3D-printed Concrete Structures). The N3XTCON pro- this case study. Specifically, our focus was on validating the ject consortium includes: Aalborg Portland A/S; Bjarke Ingels feasibility of using FutureCEM for 3DCP applications while Group A/S; COBOD International A/S; CRH Concrete A/S; Dan- highlighting the key aspects related to architectural design, ish Technological Institute (Project Coordinator); FB Gruppen material development, 3DCP process setup, and fabrication A/S; Henning Larsen Architects A/S; NCC Danmark A/S; Pen- of a concrete element. These aspects were briefly presented sionDanmark Ejendomme Holding K/S; Technical University in this publication and the readers are welcome to contact the of Denmark; and University of Southern Denmark. N3XTCON project to discuss any further details that were not covered in this article.

Final considerations The presented N3XTCON case study showcases that 3DCP calls for a holistic design-to-production strategy, and that it has a great potential to change the way we build. The case study outcome, in the form of a “twisted column”, provides insights on digital fabrication using 3DCP; specifically:

• the mix design and process parameters are discussed and serve as guide for future applications, let alone the further development of numerical models describing 3DCP process, • FutureCEM serves as a sustainable alternative binder to the typical CEM I in 3DCP applications, • inline mixing of CAC slurry proved useful to modulate the materials’ early-age structural build-up, and Danish Technological Institute • penetration tests proved suitable to map the structural Gregersensvej 4, 2630, Taastrup, Denmark build-up in highly reactive binder systems. [email protected]

References 1. R. Buswell, W.R. Leal da Silva, S.Z. Jones, J. Dirrenberger. 8. SCM – Manufacturing of highly reactive Supplementary Cementitious 3D printing using concrete extrusion: A roadmap for research. Materials for low-CO$ cement. Hoejteknologifonden (095-2010-1) Cement and Concrete Research, 112 (S.I.): 37-49, 2018 9. Green Concrete ll - Green transition of cement and concrete production 2. R. Comminal, W.R. Leal da Silva, T.J. Andersen, H. Stang, in Denmark. Available at: http://www.gronbeton.dk/ J. Spangenberg. Modelling of 3D concrete printing based on 10. Aalborg Portland RAPID® cement CEM I 52,5 N (LA) - Environmental computational fluid dynamics. Submitted to Cement and Product Declaration. Available at: https://www.epd-norge.no/sement/ Concrete Research (January 2020). aalborg-portland-rapid-cement-cem-i-52-5-n-la-article1654-324.html 3. S. Andersen, W.R. Leal da Silva, I. Paegle, J. Henrik. Numerical 11. AALBORG WHITE® cement CEM I 52.5 R – SR5 (EA) - Environmental Model Describing the Early Age Behavior of 3D Printed Concrete – Product Declaration . Available at: https://gryphon4.environdec.com/ work in progress. Submitted to the Digital Concrete 2020 (July 2020) system/data/files/6/13913/S-P-01276%20Aalborg%20White%20 4. N. Roussel. Rheological requirements for printable concretes. Cement.pdf Cement and Concrete Research, 112: 76-85, 2018 12. D. Lootens, P. Jousset, L. Martinie, N.Roussel, R.J. Flatt. Yield stress 5. N. Roussel, H. Bessaies-Bey, S. Kawashima, D. Marchon, K. Vasilic, during setting of cement pastes from penetration tests. Cement R. Wolfs. Recent advances on yield stress and elasticity of fresh and Concrete Research 39(5):401-408, 2009. cement-based materials. Cement and Concrete Research, 13. W.R. Leal da Silva, H. Fryda, J-N. Bousseau, P-A. Andreani, T.J. 124: 105798, 2019. Andersen. Evaluation of Early-Age Concrete Structural Build-Up for 6. V. Mechtcherine, F.P. Bos, A.Perrot, W.R. Leal da Silva, V.N. Nerella, 3D Concrete Printing by Oscillatory Rheometry. Advances in Additive S.Fataei, R.J.M. Wolfs, M. Sonebi, N.Roussel. Extrusion-based additive Manufacturing, Modeling Systems and 3D Prototyping. AHFE 2019. manufacturing with cement-based materials – Production steps, Advances in Intelligent Systems and Computing, 975: 35-47, 2019. processes, and their underlying physics: A review. Cement and Concrete Research, 132(-): 106037, 2020. 7. Aalborg Portland (Cementir Holding S.V.). Miljøredegørelse 2018 grønt regnskab og arbejdsmiljø. Availabe at: https://www.aalborgportland. dk/wp-content/uploads/2019/07/ap_miljoredegorelse_2018.pdf

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3_cpt_2002_14-31_Research_Development.indd 31 07.05.20 14:52 GREEN WAY TO !D PRINT Geopolymer concrete

French chemist and professor Joseph Davidovits coined the term “geopolymer” in 1978. Geo- polymers are inorganic materials with a polymeric structure of molecules. They possess high strength and a range of specific properties. They are named geopolymers because the raw materials used for their production are mainly minerals of geological origin. They possess high strength and a range of specific properties. Geopolymer cement and geopolymer concrete represent just one of the many possible applications of geopolymer materials. Companies use geopolymer technology for the production of low-temperature ceramics, fire-proof and heat-resistant composites, and toxic and radioactive waste encapsulation.

Andrey Dudnikov, Renca, Russia

Examples of geopolymer cement used in construction can be found in Australia, Ireland, the United States, and Russia, to name a few. For instance, in 2014, an entire airport in Brisbane, Australia, was built with a geopolymer-based concrete. In the Unit- ed States, special high strength geopolymer concretes have been used for airfield and road repairs. Metropolitan tubings and elements of load-bearing structures are also produced. In 2019, Renca invent- ed a unique geopolymer concrete to build a pedes- trian bridge in Skolkovo, Russia.

In Russia, there is a rich history of the development of alkali-activated materials that started in the 1950s. The research was conducted by the Kyiv Institution of Civil Engineering, guided by Gluk- hovskiy V.D. Various objects were built, including the ones in civil and industrial construction. Exam- ples include a residential house in Lipetsk, part of the railroad concrete ties in Moscow, a motorway in Magnitogorsk, and surfacing of the tank training battlefield near Chelyabinsk.

But one should not mix geopolymers and alkali- activated materials and the terms.

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4_cpt_2002_32-37_Materials.indd 33 07.05.20 14:58 History Advantages Characteristics Sustainability Application 3D printing En Ru

geopolymer cement

géocement — new environment-friendly cement, based on geopolymer technology

They are called "geopolymers" because the raw materials used for their production are mainly minerals of geological origin.

History

French chemist Joseph Davidovits coined the term "geopolymer" in 1978. Russian engineers of Renca company suggested the term géobeton as a particular case for construction materials based on geopolymer binders.

Examples of geopolymer cement used in construction can be found in Australia, Ireland, the United States, and Russia, to name a few. For instance, in 2014, an entire airport in Brisbane, Australia, was constructed with a concrete based on geopolymer binders. In the United States, special high strength geopolymer concretes have been used for MATERIALS bearing structures are also produced.

research was conducted by the Kyiv Institution of Civil Engineering, Geopolymers are not alkali-activated materials guided by Glukhovskiy V.D. Various objects were built, including civil and The similarity of the raw materials applied in both technolo- In 3Dindustrial printing, construction. geopolymer Examples include mortar a residential can be house superior in Lipetsk, in both per- gies has led to significant misconceptions about the term ge- formancepart of the and railroad also concrete cost ties compared in Moscow, a motorwayto Portland in cement-based opolymer. In fact, many scientists and civil engineers, to this products.Chelyabinsk, Geopolymer to name a few. is designed as a final product, for ex- day, use the terms interchangeably, without understanding ample a repair mortar, or a 3D printing mortar. In addition, ge- what they really are. opolymer concrete has particular chemical features that are far more beneficial for 3D printing technology. The adhesion Firstly, alkali-activated materials (AAM) are not polymers, so of geopolymer concrete is so strong because it is a chemical they cannot be called geo-polymers. Geopolymers are not a bond. Its unique properties solve the concerns with interlayer subset to AAM because they are not a calcium hydrate alterna- building in 3D printing. Namely, that Portland cement layers tive, the main component of AAM, and Portland cement pro- can be rife with cold joints if not managed properly. This will duction. In contrast, a geopolymer has a three-dimensional never happen with geopolymer concrete because it chemical- inorganic mineral substances, the production of which does not require polymeric framework of chemically-bonded atoms of silicon ly bonds to itself. You can stop printing today and continue the additional use of natural resources, and does not lead to CO2 and aluminum.emissions into the atmosphere (byproducts of metallurgical, the next day without special treatment of the surface and electrometallurgical industries and power plants). without risking the formation of a cold joint. The second fea- Main benefits of geopolymer concrete ture is its natural, rapid-strength development. This makes it Geopolymer concrete is chemically inert to a range of aggressive Geopolymersubstances and concrete remains sturdy is manufactured in severe climates. In usingcomparison 90% to less CO! perfect for mobile 3D printing. comparedtraditional to concrete traditional production Portland technology cement. based on portland Depending cement, on mix composition,geopolymer concreteit can hasbe been stronger, shown to possesschemically superior resultsinert in to a range About Renca of aggressive substances, and remain sturdy even in severe Marina and Andrey Dudnikov (co-founders of Renca) started insulation, corrosion, and aggressive substance resistance including climates.some types Geopolymer of acids. concrete has in some studies been out working for an innovative department of a construction shown superior results in strength, durability, freeze-thaw company in their home city. They were developing new ma- resistance,Besides, thefire use resistance, of geopolymer heatcement insulation, reduces CO2 emissions corrosion, by up to and ag- terials and alkali-activated concretes, and their application in gressive90% comparedsubstance to portland resistance, cement production. including Geopolymer some cement types can of acids. real construction. Marina’s father had his Ph.D. in alkali-acti- be formulated to re-use and recycle industrial byproducts. vated materials from Kyiv Institute, where the technology was Geopolymer cement can also be formulated to reuse a multi- born more than 30 years ago, so they had a near first-hand tude of industrial by-products, including plastics. source of information.

Main properties of geopolymer Main Properties

Géobèton exceeds the properties of natural stone Chemical Resistance

Geopolymer concrete is high Fire Resistance resistance to various acids and Unlike ordinary portland cement- aggressive substances, as well as based concretes, water in high sulfur resistance due to the geopolymer concretes easily absence of alcium compounds in evaporates (not bound on a its structure. molecular level) and does not explode the concrete from inside. Superior Waterproof Properties Thermal Insulation Excellent waterproof properties Properties are achieved thanks to its Materials and plasters using high- inherent mesoporous structure. quality aggregates and Big molecules like water can't geopolymer cement have superior enter in the geopolymer matrix thermal insulation. even if they are pushed using external forces. Fast Strength Thermal Resistance Development Geopolymer concrete develops Geopolymer concrete is resistant about 50% of its strength in the both to high temperatures over 1000 °C (1832 °F) and to low increases the construction speed. temperatures due to a high level of freeze-thaw resistance.

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Sustainability Utilisation of by- Cost effectiveness products Geopolymer cement Higher-level compressive Speed of the project strength and axial tension production reduces CO2 Utilizes waste and implementation increases strength, freeze-thaw due to fast strength emissions by 90% in byproducts of existing resistance, water comparison to OPC industries. development. No additives production. impermeability and resistance to abrasion in comparison to OPC.

Insulation Resistance to Thermal Shock

High Level of Freeze-thaw resistance Fire Resistance

Thixotropy Flowability

Adjustable Setting Time Constantly High Strength

from 0 to 180 minutes strength over 13 P (1885 psi)

Resistance to Corrosion Resistance to alkalis, salts, and acids

Environmental Impact and Sustainability

With population growth and the corresponding increasing demand in concretes and cements, ecological aspects of building have become a major concern of our generation.

2 globally.

Introduction of the geopolymer technology in the production of concrete with traditional portland cement production:

reducing CO2 emissions up to 90% in the production process; a minimum 60% less impact on the environment by reducing the need to extract raw materials; recycle and reuse of wastes and by-products of the existing industries.

Geocement is a material of the future. It reduces the global warming

impact by reducing CO2 emissions into the atmosphere. It has a far more eco-friendly production process and actually uses various industrial wastes and by-products.

Buildings constructed with geocement earn additional LEED points compared to conventional construction materials.

Green Building

Green building brings together a vast array of practices, techniques, and skills to reduce and ultimately eliminate the impacts of buildings on the environment and human health. It often emphasizes taking advantage of renewable resources, e.g., using sunlight through passive solar, active solar, and using plants and trees through green roofs, rain gardens, and reduction of rainwater run-off. Many other techniques are used, such as using low-impact building materials or packed gravel or permeable concrete instead of conventional concrete or asphalt to enhance the replenishment of groundwater.

A green building is one which uses less water, optimizes energy provides healthier spaces for occupants, as compared to a conventional the world. By adopting Green methodologies, we would be able to reduce the carbon footprint and would be helping the environment.

cost of the usual ingredients of concrete has forced the construction engineers to think of ways and means of reducing the unit cost of its production. At the same time, increased industrial activity in core sectors like energy, steel, and transportation has been responsible for the slag, silica fume, and quarry dust with a consequent disposal problem.

Application

Geocement can be used in a wide range of applications in different industries.

Examples of industries where geopolymer cement-based products can be applied:

General construction Earthquake-proof construction and buildings Concrete blocks Road construction Concrete pavements Eco-friendly green building Containers and tanks for various liquids Pre-cast concrete Bridge constructions Railroad slippers Modular houses 3D-printing Sewer systems Various infrastructural projects Fire-proof systems Radioactive substances containment / encapsulation systems Marine structures Piles, foundations and other subterranean structures Petrochemical constructions Architectural constructions Architectural design and decoration Countertops, panels and other concrete goods

RENCA 3D geopolymer ink

Together with the introduction of 3D-printing technology in construction, geopolymer binders and geobetons on their base make a new step in development. And already widely used in this technology of buildings construction.

Fast Cost Effective Sustainable

About 100 m2 accommodation in 24 hours. No waste, faster construction period. Due to the use of industrial by-products CO2 emissions are reduced by up to 90% in comparison with the traditional technology.

Get the latest news about geopolymer concrete for 3D printing! visit www.renca.org

MAIN SITE NAVIGATION CONTACTS

Visit our main site: History RENCA www.renca.org Properties +7 (495) 649 02 86 Online call Architectural concrete: Advantages www.geobeton.ru RENCA © 2015 2020 Characteristics +1 (702) 605 00 08 Sustainability Application +971 (0) 50136 9586 3D printing [email protected]

registration number 1167456053280 , 7430025313 1167456053280 MATERIALS

Geopolymer concrete has particular chemical features that are beneficial for 3D printing technology.

What bothered them was that a"er more than ten years of of construction with a consistently high mechanical strength experience in alkali-activated concretes, they still found its (compressive strength reached 92 MPa (13300 psi)). In addi- properties to be unstable and, in most cases - unpredicta- tion, the elaborated formula of geopolymer 3D printer ink was ble. Andrey and Marina started to do more research and got highly suitable for the technology of 3D printing due to a high- acquainted with geopolymer technology. In 2015 they went er thixotropy, fluidity, and an ability to adjust the setting time. to Geopolymer Camp in Saint-Quentin, France, where they learned from Professor Davidovits and met their business 2017 partner, geologist-mineralogist Alex Reggiani. In 2016, they Renca was a part of Dubai Future Accelerators in UAE and formed Renca and began extensive research and develop- signed an MOU with Dubai Municipality for developing a ge- ment of various applications of geopolymer technology in the opolymer mortar based exclusively on local raw materials for construction industry. 3D construction printing. The first trials with 3D printed geopolymer concrete were made in severe Siberia, where there, for the first time, suc- 2018 cessfully tested geopolymer concrete for a mobile 3D print- Renca successfully applied geopolymer mortar for 3D con- er was made by the company Apis Cor. The experience was struction printing in the harsh climate of Northern Russia for unique. Both technologies were at the early start of entering a project with Gazprom Ne", an oil and gas company. The mo- the construction market. They were pioneers in construction bile robotic arm 3D printer was used for this project. 3D printing and believed that the future was in eco-friendly construction. Renca awarded the first prize in Katerva Awards, in the Ma- terials, Resources & Water category. RENCA was named one Once an ideal consistency for 3D printing was reached, the of the top 100 innovative, disruptive construction companies tests confirmed the high e#iciency of geopolymer concrete. according to Disruptor Daily, and became one of the Top-50 The natural rapid strength development shortened the time companies, o#ering solutions for smart-buildings.

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2019 Renca, in collaboration with 3D-printing companies and universities, extensively tested geopolymer 3D ink on di#erent 3D construction printers. Based on these tests, the industrial production of geopolymer 3D ink started in 2020.

Renca geopolymer 3D mortar is now a part of the Material Connexion library in New York as one of the most innovative materials not only for 3D printing but for the construction industry in general.

“I believe that in the near future, 3D printers will become another instrument for the construction industry, as common as hammers or concrete mixers - one may even be able to buy it in a local hardware store” —

Marina Dudnikova, Business Development Director, Renca

The plans for the future Renca’s production facilities are located in Russia and Italy, and the products can be shipped worldwide. In 2020 Renca will begin industrial production for the US market.

Renca deliver all-in-one solutions Renca, in collaboration with its partners, including 3D printers and automatic can o#er a complete, all-in-one solution, in- mixing system for concrete cluding 3D printers, mortars, mixing machines. They work together with suppliers of industrial robots for robotic arm solutions, and gantry-type 3D printer. It is estimated that less than $100,000 can get you a working solution for the construction of houses. This provides real a#ordable housing and speeds up the development and spread of 3D construction printing technology.

Since 2016, Renca have tested and adjusted geopolymer mortar for 3D printing on most existing types of 3D construction printers. Renca knows what their clients need and how to adjust the recipe according to their specific requirements.

Renca Inc. T +7 495 6490286 [email protected] www.renca.org

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4_cpt_2002_32-37_Materials.indd 36 07.05.20 14:59 MATERIALS PARTNERSHIP TO DEVELOP PRINTABLE CONCRETE Specially formulated concrete

The Quikrete Companies and the U.S. Department of Ener- advanced and economical “concrete inks” to supply all varie- gy’s (DOE) Oak Ridge National Laboratory (ORNL) recently ties of 3D concrete printers. We are optimistic that this tech- entered a cooperative research and development agree- nology will be a game changer for the concrete industry and ment to design next-generation concrete for use in the revolutionize the construction practice,” said Chuck Corn- production of large-scale structures through a 3D printing man, Chief Technology O#icer at The Quikrete Companies. process. “We look forward to working with Quikrete, developing a nov- Using additive manufacturing system developed by ORNL, el material for large-scale construction, and we anticipate this the collaboration with Quikrete will deliver specially-formu- project will have significant industry impact,” said Brian Post, lated concrete that establishes new construction capabilities. R&D Scientist at ORNL. “As a leader in advanced manufactur- In alignment with the DOE’s Advanced Manufacturing O#ice’s ing, DOE’s Manufacturing Demonstration Facility at ORNL is Multi-Year Program Plan, Quikrete and ORNL are developing uniquely suited to advance this technology.” a concrete mix with the strength, curing time, and durability to construct buildings, energy installations, transportation The partnership will leverage ORNL’s scientific expertise and infrastructures and other large-scale structures faster, more its unique facilities along with Quikrete’s robust experience in a#ordably and with less energy consumption. the plastic and hardened properties of cement-based building materials. The two-phased collaboration, which is the first Designed as a pumpable, low- or zero-slump material that between Quikrete and ORNL, concludes in two years. sets quickly and gains strength rapidly, this new concrete will be ideal for printable construction projects. In addition, the one-of-a-kind concrete will meet tensile strength, compressive strength, ductility and other structural performance characteristics required as a viable building material.

“Oak Ridge National Laboratory is one of the most advanced The QUIKRETE Companies players on the global additive technology stage. Quikrete is 5 Concourse Parkway not only a leader in concrete technology, but also second-to- Suite 1900, Atlanta, GA 30328, USA none in construction materials manufacturing and logistics. T +1 404 6349100 Working together, Quikrete and ORNL can quickly develop www.quikrete.com

Publisher of trade journals for the construction materials industry

www.cpi-worldwide.com

2002_allgemein_174x60mm_CPI_en.indd 1 02.05.20 19:29

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INDUSTRIAL CONCRETE PRINTING SOFTWARE

Specifically designed to assist research and industry

RAPCAM Concrete is an industrial manufacturing so! ware

So! ware support for 3D concrete printing hardware has ware package is an industrial manufacturing so! ware com- been almost unavailable. Where research and develop- pletely dedicated to the high volume production of large scale ment departments rely heavily on the flexibility of skilled concrete printed objects. To deliver on this promise RAPCAM CAD modelers and Grasshopper specialists to quickly test o" ers its users much more than just a slicer. new hardware features, manufacturers that are looking for consistent, reliable and easy to use so! ware have Utilizing cloud-based standards found themselves without any good options. One of the most fundamental architectural features is the cloud-based Project Management Environment. Although From the experience in robotic manufacturing so! ware and common in any cloud storage provider like Google Drive or a three-year development process for a custom printing ap- Dropbox, keeping track of files, versions, machine instruc- plication for Bruil Prefab Printing, Dutch so! ware vendor RAP tions and log files isn’t just a nice-to-have anymore. For relia- Technologies has now consolidated its knowledge in a prod- ble manufacturing it has become essential. uct for a wider audience: RAPCAM Concrete. RAPCAM allows its users to manage tasks and files across pro- For Industrial 3D Concrete Printers jects, and processes them in a standardized, controlled fash- Where many companies are still relying on so! ware that has ion. At any moment in the process users can quit and their been built for DIY plastic printers, the RAPCAM Concrete so! - progress will be stored in the task they were working on.

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Minimizing mistakes with a structured workflow spiral modes, transitions and many more. This module can The RAPCAM concrete workflow consist of three easy steps also show you whether your print contains inclined parts that that shouldn’t take more than a couple of minutes to com- might be challenging to print. You can also get great 3D visual- plete. izations of the printed element to send to your client.

Analysis Simulation As a first step, single or large amounts of 3D models can be The sliced object that was configured in Product Setup can loaded into RAPCAM for analysis. Having users work in their now be assigned to the right machine and production posi- own favorite CAD packages we support the industry-wide tion. As clients can run multiple printers, including both ro- standard STEP file format as well as others. To quickly re- botic arms, gantries and combinations, the printing process spond to either clients or colleagues about the validity of their can be accurately checked in a 3D simulation including colli- 3D model, the geometry is first checked on its format, model sion detection to make sure there are no errors to be expect- type and size. ed. For that purpose, custom hardware including end-e"ec- Results from this analysis can be quickly returned to provide tors, external axes, pumps and mixers can all be integrated designers and engineers with the information they need to into the simulation. improve or change their models. Immediately a!er simulation, an instruction set can be gen- Configuration erated into the machine-specific format, whether it’s a Sinu- As the core of any 3D printing application the object is sliced. merik, ABB or Kuka controller or a generic GCode. Machine The 3D model can be configured with horizontal or dynamic feedback can be logged for quality control purposes and read slicing, o"sets types, layer height and -width, concrete type, back to be included in the task details.

RAPCAM allows its users to manage tasks and files across projects

3D simulation of the printing process

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®Bruil Prefab Printing ©Kokon Architectuur & Stedenbouw

Bruil Prefab Printing in Veenendaal, the Netherlands

Showcase Being in control The power of RAPCAM’s underlying technology can be wit- Concrete printers and mortars are under rapid development nessed at Bruil Prefab Printing in Veenendaal, the Nether- and the quality of a print is extremely dependent on how lands. As our client Bruil started three years ago with a fixed these two are combined. The specific limitations and possi- robotic arm and is now running a highly customized version bilities that arise from this combination has to continuously of RAPCAM to control a built-to-purpose 3D Concrete Printer adapt. based on a Kuka K120 R3900 and a 34m linear track. The ability to assign specific workflows and permissions to The project that is launching Bruil’s e"orts in 3D Concrete users can be used to reflect any companies chain of command Printing into the spotlight is the renovation of two 1970’s and reduce mistakes. To make sure that users can work with- apartment buildings in Den Helder (detailed report in CPT in the continuously changing boundaries, RAP Technologies 1/2020). The project, designed by Kokon Architecten, uses allows administrators to add or change limits on layer height 3DCP for its aesthetically pleasing features on the outside of and -width, overhang, printing speed or output for materials the building. These are non-load bearing elements that ap- and tools. In this way, settings used for testing and accepta- pear Gaudiesque. The project contains 125 custom designed tion can later be released for production. elements for a total of 1200 printed elements; an engineering feat never shown before.

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In Den Helder flats will be upgraded entirely with 3D printed concrete elements.

To get started with your own materials and tools, RAP Tech- nologies provides its setup service free-of-charge for machine-builders, equipment- or concrete manufacturers and end-users that require support for their machinery or material in RAPCAM Concrete, even if they are the only one using it. RAP Technologies B.V. Scheepsbouwweg 8 – K10 3089 JW Rotterdam, The Netherlands Outlook T +31 10 3076365 The incredible progress being made in all aspects of the 3DCP [email protected] ecosystem provides a continuously demand for new features. www.raptech.io For its second release planned for fall 2020, RAPCAM Concrete will include more advanced features aimed at eliminating failed, deformed or collapsed prints and increasing the possibilities of printers including: material open-time analysis, adaptive layer height, dynamic printing speed and, if all goes well, support for FEA analysis based on non-linear material properties.

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!D CONCRETE PRINTING WITH AN INDUSTRIAL ROBOTIC ARM Next step towards digital project implementation

Besix Group, founded in 1909, is a leading Belgian company, mainly active in the construction, real estate develop- With 3D concrete printing, ment and concession sector. Over the years, the group has Besix Group is taking the next step towards digital project experienced enormous growth and has gained a great deal implementation. of know-how and experience. Among other things, this has ensured that the company has evolved from a valued construction partner to a company that can o!er a complete service package.

This allows Besix Group to take on any project, whatever its size, including financing, design, construction and maintenance. The last few years, the company has focused on diver- sifying its activities, both geographically and across sectors. This has been made possible thanks to a strong organizational policy and some acquisitions and participations. Meanwhile, Besix Group is active in 25 countries on 5 continents. It can certainly be stated that Besix Group is a company of which the last has not yet been seen or heard. Their motto is therefore „To excel in creating sustainable solutions for a better world“.

Technological progress in the construction sector thanks to 3D concrete printing The construction sector has always been very close to Besix Group‘s heart, which is why it is the company‘s core business. In recent years, the construction sector has been catching up strongly in terms of digitization and innovative tools. This technological progress is mainly in the design and engineering of buildings and constructions. With 3D concrete printing, Besix Group is taking the next step towards digital project implementation.

Besix Group first models all elements itself via the 3D so!ware Innovation through Partnership Revit and Grashopper. This so!ware will then drive the Kuka Besix Group is therefore more than satisfied with their choice KR120 R3900 robot. This robot is equipped with a nozzle for to use a Kuka KR120 R3900 robot for this application. Be- 3D concrete printing. cause 3D concrete printing with an industrial robot arm was something new for them too, it was important to find a reli- More possibilities thanks to 3D concrete printing able partner who was willing to think along with them. Kuka This Besix Group 3D concrete printing application greatly and Besix Group took a close look at the application and dis- increases the design freedom in the engineering phase, au- cussed the possible steps in this process. tomatically presenting a wider range of possible solutions to customers. As a result, customers are no longer bound to Thanks to this intensive qualitative collaboration, Besix standard designs. Because the model is printed in 3D with a Group succeeded in developing and implementing a success- Kuka robot, it is also possible to always create the same prod- ful, innovative robot application. Due to the great success of uct with less waste and this at a much higher speed. This also 3D concrete printing with a Kuka robot, Besix Group is even increases Besix Group‘s production capacity and all o" this in thinking of expanding their production facility in Dubai or a a much safer, controlled working environment. similar setup in Belgium or the Netherlands.

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More possibilities thanks to 3D concrete printing

www.kuka.com

www.besix.com

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!D PRINTED STAIR MOLDS Reach new design heights

Aectual Stairs converts conventional concrete formwork techniques into works of art. The 3D printed stair molds can take virtually any shape and are 100% sustainable.

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Aectual Stairs converts conventional concrete formwork techniques into works of art.

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6_cpt_2002_42-59_Production_Application.indd 46 07.05.20 15:25 Aectual’s unique 3D printed formwork is made from recyclable bioplastic PRODUCTION & APPLICATION

Aectual Stairs are produced in several types of concrete, with help of the unique 3D printed formwork technology. 3D printing enables unprecedented designs. So! chamfers, patterns, orna- ments, or logos can all be easily integrated into the formwork and thus into the final concrete stairs.

Break free from conventional formwork Aectual’s unique 3D printed formwork is made from recyclable bioplastic. A!er use it can simply be shred and directly re-printed into new formworks. This brings unequaled design possibilities, and faster and cheaper production that’s much less wasteful than conventional production methods. Also, with help of the design & engineering so!- ware Aectual can optimize the shape of the stairs and reduce the amount of concrete needed.

Sustainable materials Aectual stairs are made of conventional concrete with steel reinforcement, and Aectual Stair - made of conventional ranges in colours from white to dark concrete with steel reinforcement grey. Di"erent finishes are possible, as well as Ultra High-Performance Con- crete stairs, which don’t require reinforcement and can be up to 6 cm thin.

From unique design to engineered product in an instance Aectual design so!ware combines para- metric design-, engineering- and digital manufacturing constraints. This enables a fast and smooth design & build process and guarantees safe and certified production.

Aectual Asterweg 149 1031 HM Amsterdam, The Netherlands T+31 (0)20 229 1786 [email protected] www.aectual.com

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CONTOUR CRAFTING: A REVOLUTIONARY PLATFORM TECHNOLOGY Pioneer of construction 3D printing

Contour Cra"ing (CC) is a mega-scale fabrication process that enables additive fabrication of large-scale objects directly from computer models. CC simultaneously uses computer-controlled extrusion and troweling to achieve smooth and accurate free-form surfaces. CC has been enabled by many unique technologies in robotics, material delivery, and control systems that have been created over the course of a few decades. The CC concept was first proposed by Behrokh Khoshnevis at the University of Southern California in 1997, and years later it initiated the field of construction 3D printing. In 2017, Contour Cra"- ing Corporation (CC Corp) was founded to commercialize this technology using the investment from the Umdasch Group Ventures. CC Corp is the first funded start-up in this domain with a mission to commercialize the revolutionary CC technology as well as other innovative technologies. CC Corp technologies use specially designed robotic systems Figure 1: A demonstration project using the CC technology to quickly construct structures using data from CAD models. While there are numerous applications for these technologies, CC Corp is initially focusing on transforming and revolutionizing house construction. Building Construction CC technology uses modern robotics and specially designed concrete mixtures to build custom designed houses in one or Behrokh Khoshnevis and Ali Kazemian, few days. CC has the potential to transform the global con- Contour Cra!ing Corporation, El Segundo, California struction industry. Construction could become a consumer market, wherein a house or other structure could be designed and built by the family that will occupy it. Reduced construction costs and time will make construction accessible to an- In CC, computer control is used to take advantage of extru- yone. Cost analysis results show that the cost of insulated sion and the superior surface forming capability of troweling walls built by the CC technology is about 25% of the cost of to create smooth and accurate, planar and free-form surfaces. insulated conventional concrete masonry units (CMU) walls. It provides architects the flexibility to design organic curved CC process could also reduce the environmental impacts of surfaces as easily as traditional rectangular shapes (Figure 1). construction due to a reduction of both waste and emissions, With the level of automation possible by the CC technology, as well as lower energy use. Another aspect is related to in- orders of magnitude in time savings are anticipated, com- juries and fatalities that frequently happen at construction pared to conventional construction methods. sites. Each year 400,000 workers get seriously injured or killed in construction in the US alone. CC technology eliminates Currently, almost all of the activities in the field of construc- such hazards and fatal accidents during construction, while tion 3D printing is limited to the building shell construction. In reducing a worker’s exposure to hazardous and airborne sub- this article, the CC technology is described as a platform tech- stances such as dust and chemicals. CC technology seems to nology which has shown great potential to be used in various be an ideal solution for massive construction of low-income domains. In the following sections, several important appli- housing around the world, and emergency reconstruction by cations of this technology and the relevant implementation disaster relief agencies working in areas devastated by earth- details are discussed. quakes, floods, wars, and other natural disasters.

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Currently, almost all of the activities in the field of construction 3D printing is limited to single-unit one-story buildings. However, with the advancement of the technology and addressing the regulatory barriers, a wide range of buildings could be 3D printed. Figure 2 presents three variations of the CC technology which are designed to build detached houses, multi-story buildings, and multi-unit large structures.

Another major limitation with the current construction 3D printing systems is related to the fact that only the construction of the building shell (walls) is automated by these systems, while other activities are performed by traditional manual approaches. Considering the fact that building shell construction cost is typically less than half of the total construction cost, this is a major shortcoming which should be addressed in the future generations of the construction 3D printing systems. In the following paragraphs, perspectives and implementation details for automation of other major construction tasks using the CC technology are provided.

Once the CC robotic infrastructure is in place several robotic manipulators may be added to eventually achieve total automation of building construction. Considering major achievements and advances in manufacturing using robotics, the total automation of building construction seems possible. Today many complex products are accurately produced by robotic systems in fully automated manner. Buildings are Behrokh Khoshnevis is the president and CEO of Contour Cra!ing relatively simpler with respect to geometry and required accuracy. The layer-wise Corporation and the Louise L. Dunn fabrication paradigm used by Contour Cra!ing should now allow the realization of Distinguished Professor of Engineer- automation of total building construction. ing at the University of Southern Cali- fornia. He is a member of the National Academy of Engineering and a Fellow of the National Academy of Inventors. A

Detached Houses

Ali Kazemian is a senior R&D engineer at Contour Cra!ing Corporation with six years of experience in construction 3D printing. He received his PhD from the Univer- sity of Southern California, where his research was focused on developing real-time quality monitoring Multi-Story Buildings measures for construction 3D printing using innovative techniques such as computer vision. ali.kazemian@contourcra!ing.com C

Figure 2: Di"erent scenarios for automated Multi-Unit Large Structures building construction using CC technology

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Figure 3: Automated Tiling

Automated tiling of floors and walls solder, and once the alignment is made, bonds the two pipe Tiling of floors and walls may be automated by robotically de- segments. Other universal passive (requiring no active open- livering and spreading grout and other material for adhesion ing or closing) robotic gripper and heater mechanism designs of tiles to floor, as shown in Figure 3. Another robotics arm used for various plumbing components are also shown in the can then pick the tiles from a stack and accurately place them figure. Note that PVC plumbing is also possible in which adhe- over the area treated with the adhesive material. O!en 60% sives may be used for pipe connections. of the time in manual tiling could be spent on alignment. With a robotic infrastructure in place alignment could be done Automated electrical and communication line wiring quickly and accurately. A modular approach similar to industrial bus-bars may be used for automating electrical and communication line wir- Automated plumbing ing in the course of the CC process. The modules, as shown in The Contour Cra!ing process is able to build utility conduits Figure 5, have conductive segments for power and commu- within walls. This makes automated plumbing possible. In nication lines, and inter-connect modularly. All modules may this arrangement, a!er fabrication of a certain number of wall be robotically fed and connected. A simple robotic gripper on layers, a segment of copper (or other material) pipe may be manipulator attached to a CC machine can perform the task attached onto the lower segment already installed inside the of grabbing the component and connecting it to the compo- conduit. The robotics system, shown on the le! side of Figure nent already placed within the conduit. The automated con- 4, delivers the new pipe segment and has a heater element struction system properly positions these modules behind (shown in red) in the form of a ring. The inside (or outside) the corresponding openings on the walls. The only manual rim of each pipe segment may be pretreated with a layer of part of the process is inserting fixtures into the automatically solder. The heater ring heats the connection area, melts the constructed network.

Figure 4: Plumbing modules & grippers

Figure 5: Electrical modules

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Automated imbedding of sensors and computational devices farms is very significant (about $30M for a wind farm having Construction materials such as smart concrete may be used in about 100 installations). the CC process in certain segments of the building. Such materials demonstrate varying resistance under stress conditions. The alternative tower construction method based on the CC Also, discrete sensors may be densely placed by a robotic arm technology is motivated by the aforementioned high costs at pre-specified locations inside any type of construction ma- associated with steel segment fabrication, transportation, terial (e.g., conventional concrete). These sensors can be use- gigantic cranes, labor needed for assembly, and road con- ful for in-process feedback for construction process control, struction. and in completed structure as means for inspection and for creation of smart structures that sense various variables such Contour Cra!ing approach is based on using concrete and as temperature, humidity, stress, vibration, etc. automatically constructing towers by means of: a) robotic system that can climb the tower as it is being constructed by a Automated insulation, finish work and painting novel construction module, b) the construction module based Insulation as well as finish work such as plastering of walls on Contour Cra!ing (a large-scale 3D printing system), and c) may be achieved by using a hybrid CC nozzle that concur- a novel material delivery system. The robotic system keeps rently delivers multiple materials such as concrete, polyure- the construction module that it carries well aligned in such a thane, and plaster. A!er walls are constructed a conventional way that the final tower ends up having near-perfect geome- spray-painting robotic manipulator driven by the same CC try and orientation with respect to the horizon. A small-scale machine may paint each room according to desired specifica- version of the system has been constructed and the feasibil- tions. The painting mechanism may be a simple spray nozzle, ity of the concept has been proven. Future plans of CC Corp or a large inkjet printer head (such as those used for printing include the development of full-scale CC tower builders. large billboards). The major advantages of the new approach are:

Infrastructure • Fully autonomous operation Many types of infrastructure elements may be automatically • Usage of concrete that eliminates factory work on steel built with the CC technology. For example, a variation of CC segments and di"icult transportation technology for autonomous construction of tall concrete tow- • Safe operation due to elimination of human tasks at risky ers has been proposed, which applies to wind turbine towers, elevations and windy condition bridge pylons, water towers, silos, chimneys, etc. The method • Low cost of transportation employs a set of coordinated vertically climbing robots that • Possibility of building much taller towers carry a special Contour Cra!ing nozzle assembly and motion control system and a special method of cementitious material delivery system. Implications for wind turbine towers is further elaborated in the following paragraphs.

Currently wind turbine towers are constructed using hollow steel segments that are produced at factories, transported to the site at great cost, and assembled using special cranes and specialized crew. The task is very hazardous as it is performed at high elevation o!en under strong wind condition and in tight work envelope involving risks of falling, getting cut between heavy steel segments and being hit by the crane or its load or accessories. Given the current method of tower construction, the tower is the most expensive part of the entire wind turbine assembly.

The large steel sections of the tower have to be transported from the factory to the wind farm for installation. They are o!en classified as wide load which require special transportation considerations. Furthermore, there is currently a strong motivation to build taller towers that can reach stronger wind elevations. However, the current method of tower construction is limited because it is expensive to build cranes that can reach higher than the current maximum height (85 to 100 meters). In addition, taller towers require large base segments that will be hard to transport (width limitation of available roads, height limits imposed by overpasses, etc.) Further- more, large cranes will require wider roads at the wind farm. Figure 6: CC technology for automated wind turbine Currently the cost of road construction especially at hilly wind tower construction

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Figure 7: CC technologies for building immediate infrastructure on the Moon and Mars for future colonization

Space Applications A major limitation for lunar and Martian construction is the The ability to fabricate extraterrestrial habitats, laboratories availability of resources, as conventional concrete constitu- or manufacturing facilities is the key element for long-term ents (aggregate, cement and water) are either hard to obtain human survival on the Moon or Mars. Contour Cra!ing tech- or hard to manufacture using in situ resources on these ce- nology has the potential to build safe, reliable, and a"ordable lestial bodies; water is very scarce resource and also cement lunar and Martian structures, habitats, laboratories, and oth- production requires a very significant amount of processing er facilities before the arrival of human beings. and energy consumption. To address this issue, a research Special CC construction systems are being developed that ex- project was carried out in the Contour Cra!ing lab which was ploit in situ resources and can utilize, for example, lunar reg- supported by a Phase II NASA Innovative Advanced Concept olith as construction material. These structures can include (NIAC) program. In this project, sulfur concrete was investigat- integrated radiation shielding, plumbing, electrical, and ed as an alternative for water-based concrete. Sulfur concrete sensor networks. has numerous terrestrial applications and is potentially an

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Figure 8: CC robotic system used for sulfur concrete 3D printing

ideal construction material for planetary construction, espe- Summary cially on Mars which has an abundance of sulfur and a tem- The Contour Cra!ing technology was conceptualized in perature range that sulfur concrete structures can withstand. 1997, and years later it initiated the fast-growing field of con- Its availability, high strength and durability properties make struction 3D printing. CC is a platform technology with great it a very attractive construction material. The developed CC potential to be used in many application areas beyond build- process which includes preheating and mixing the sulfur and ing shell construction. In this article, several major applica- aggregate at 150# C is presented in Figure 8. tion domains for the CC technology, namely, fully automated building construction, infrastructure development, and space It should be mentioned that there are other CC Corp’s tech- applications were discussed. Experimental research studies nologies to be used along with the CC technology, in order to and demonstration projects have already proved the feasibil- realize the automated construction of extraterrestrial habitats ity of some of these novel applications of the CC technology. and infrastructure for future colonization. For instance, Selec- tive Separation Sintering (SSS) is a new 3D printing process which won the first place in the NASA In-Situ Materials Chal- lenge. While CC is an extrusion-based 3D printing process suitable for construction of large-scale monolithic structures, SSS is a powder-based method ideal for building smaller-scale objects such as interlocking tiles and bricks, as well as a large Contour Cra!ing Corporation array of functional objects such as metallic parts. SSS is the 215 South Douglas Street, El Segundo only powder-based process that can e"ectively work in zero Los Angeles, CA 90245, USA gravity condition and as such it is ideal for use in the Interna- www.contourcra!ing.com tional Space Station for fabrication of spare parts and tools.

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!D PRINTED CUSTOM BLOCK PAVEMENT AND OBJECTS New approach

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Concrete 3D printer at work

Suppliers of building materials are working on construc- Stationary 3D-printers (printing cells) based on industrial tion printing technologies to protect and boost their sales robots are o" ered as complete solutions. The reach of such of premixed material. A small startup from Austria is printing systems can be between one and four meters leading taking an opposing way – pushing hard to lower the cost to a maximum building size of around 2 x 5 m depending on of 3D printed items by o! ering an alternative to premixed the shape of the object. Extrusion of the cementitious mate- printing material. rial occurs at around 30 cm per second, whereas the extrusion volume depends on the selected extrusion diameter and Printstones was founded in 2017, and – a! er 3 years of ranges from 0,6 kg to 6 kg per minute. development – is now in the process of entering the market. The startup focuses on the development of fully-automated The application of such a concrete printing system allows the 3D printing processes for concrete and other cementitious customizable, just-in-time production of various concrete ob- materials. jects. “It doesn’t make sense for mass-production - but it does

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3D printed paving stones

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Automated construction of a pavement area – 3D-model by award-winning industrial designer Markus Tanzer-Kargl.

for mass-customization and smaller quantity product lines”, The compact design of their first mobile version is a key fea- says Dr. Hengl, one of the founders of Printstones. “We o"er ture, allowing the vehicle to fit into elevators and through complete solutions including hardware, so!ware and print- door frames. Furthermore, the use of tracks was chosen over ing material.” The systems also include fully automated ma- a wheeled platform due to the higher stability and its ability terial mixing and dosing units, which allow easy adjustment to simply move up and down stairs. of recipes towards local materials. This is a new approach, opposing the more common ready-mix material solutions. The current printable product range is still under exploration and includes paving blocks, border stones, concrete plates, molds, facade panels, counters, free-form objects, stairs and furniture for public spaces. New product ideas keep coming in from existing customers and new partners every day.

The young company is also pushing into mobile on-site solu- PrintStones GmbH tions. “Basically, it is an o"-site printing cell mounted onto Gutheil-Schodergasse 8-12 a tracked vehicle and enhanced with an autonomous navi- 1100 Wien, Austria gation technology”, says Dr. Hengl. “In a first on-site test, we o"[email protected] were able to print a paving area - by feeding the system with a www.printstones.at 3D-model and corresponding environmental data”.

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ROBOTS BRING THE IDEA FROM BIRTH TO REALIZATION 3D printing of buildings and production of non-standard concrete moulds

Robots are increasingly used in the construction process, ABB robots were used to ensure that the architects’ work was from sketching an idea to moulding it. ABB robots have accurately reproduced in concrete. The flexibility of the so! - been instrumental in the completion of many projects. ware of robots allowed architects, engineers and other pro- Let’s take a closer look at the contribution of ABB tech- fessionals to collaborate and solve problems in real-time. nology to 3D printing of buildings and the production of The big challenge was developing a concrete mix that could non-standard concrete moulds. keep up with the superhuman speed of the 3D printer and dry in record time. The project’s material experts were able Bringing 3D printing to construction to handle this. Although concrete is a naturally sustainable Digital design tools have been at the centre of building design building material, the real advantage was how little waste for decades, but construction itself has stubbornly remained was generated during 3D construction. The accuracy of the a manual process. In 2018, Arup and CLS Architetti proved printing process ensured that every centimetre of material that a combination of 3D printing robotics could change all was used. Given that 32% of today’s waste is generated in con- that. struction, this alone is a major improvement.

ABB robots were used to ensure that the architects’ work was accurately reproduced in concrete.

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6_cpt_2002_42-59_Production_Application.indd 58 07.05.20 15:31 This project showed how new technologies and creative thinking can solve long- term challenges.

Rethinking the construction industry CPT Bladerunner is a multi-stakeholder collaboration project in Denmark that wants worldwide to revolutionize the construction industry by facilitating the production of organic CONSTRUCTION PRINTING TECHNOLOGY moulds at comparable price levels to those of standard moulds. The new technology o" ers a serious alternative to the existing ones as it allows to create something di" erent from monotonous concrete structures. The trade magazine for 3D printing in concrete Bladerunner uses expanded polystyrene (EPS) for rapid production of non-standard concrete moulds. In Denmark and elsewhere, the number of architectural de- Completed projects signs with advanced geometry is growing rapidly in the construction industry, so Experiences of the pioneers there is a demand for technologies that can improve the design of architects with- Technological developments out increasing the construction budget. Scientific results Application areas Bladerunner also aims to promote the flexibility of concrete production, as each Visions of the future element can be easily adapted to di" erent shapes, sizes and materials with the help of a modular so! ware system and robots. Flexibility also facilitates on-site and much more production, including cutting jigs directly on site.

www.abb.com

With Bladerunner, each element can be easily adapted to di" erent shapes and sizes. To the newsletter:

www.cpt-worldwide.com

On registering for the newsletter, you will receive the first available issue without obligation and free of charge

6_cpt_2002_42-59_Production_Application.indd 59 07.05.20 15:31 The 400 square foot homes, 3D printedPROJECTS with Icon’s Vulcan II printer.

!D PRINTED HOMES FOR HOMELESS IN AUSTIN

Bedroom, bath, kitchen, living room and large porch

Icon, the construction technologies company, announced some risks if we want a better world for ourselves, and the team it has completed a series of 3D printed homes as part of its at Mobile Loaves & Fishes shares a similar vision in their e! orts continued partnership with Mobile Loaves & Fishes (MLF), to empower the community around them into a lifestyle of ser- the Austin non-profit widely known for its compassionate vice with the homeless. We need a radical rethinking in the way service to the area’s homeless community. that we approach solving vexing issues in our society like homelessness. At the end of the day, this is all about people and the The 400 square foot homes, 3D printed with Icon’s Vulcan II dignity of human beings.” printer, feature one bedroom, one bath, a full kitchen, living room and a large porch with sweeping sunset views. The series “The promise of Icon’s 3D printing technology is really exciting, of 3D printed homes will soon be a place for the formerly home- and what better place to start putting it to use than in one of less to call home at Community First! Village, one of the most the country’s most innovative neighborhoods designed to serve innovative communities in the world. men and women who have experienced the trauma of homelessness,” said Alan Graham, founder and CEO of Mobile Loaves “Icon at its heart is innovation for a better future,” said Jason & Fishes. “Vulnerable populations like the homeless are never Ballard, co-founder and CEO of Icon. We’re going to have to take among the first to access leading-edge anything, but now here

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The homes feature one bedroom, one bath, a full kitchen, living room and large porch and are located at Community First! Village in Austin, TX.

in Austin, Texas they’re among the first in line who will be liv- With architecture designs created by Logan Architecture and ing in some of the most unique homes ever built—and we think finishings by Franklin Alan, the series of 3D printed homes fea- that’s a beautiful thing.” ture multiple home designs that were printed simultaneously, three at a time, to further increase speed and reduce cost. The series of 3D printed homes by Icon are located in Phase II of The first set of homes are now complete, with the first individu- the northeast Austin development, bringing the entire property als to ever live in 3D printed homes in the U.S.. to 51 total acres. When Phase II is completed and at full capacity, Community First! will have an estimated 480 formerly home- DEN Property Group sponsored the interior design completion less individuals living in the Village — which represents about of the homes allowing Icon and MLF to provide furnishings, de- 40 percent of Austin’s chronically homeless population. cor and artwork to create a wonderful place for these individuals to call home. Designer, Claire Zinnecker, continued to work The 3D printed homes for the homeless were funded by MLF alongside Icon to create beautiful interiors for this series of and its supporters, in particular Cielo Property Group, who 3D printed homes receiving input from the future residents. commissioned one of Icon’s printers to be dedicated to the city of Austin to address a!ordable housing issues.

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The 3D printer, called the Vulcan II, is designed to work under the constraints that are common in rural locations.

See the Vulcano II in action!

Icon’s 3D printing construction process, which makes use of robotics, automated material handling, advanced so!ware, and a proprietary concrete, Lavacrete, o"ers a new way to quickly build homes.

Icon’s 3D printing construction process, which makes use of robotics, automated material handling, advanced so"ware, and Vulcano II a proprietary concrete, Lavacrete, o!ers a new way to quickly The Vulcan II is ICON‘s first commercially available construction build homes that are both resilient and beautiful in a price range printer. Designed specifically to produce resilient single-story significantly below comparable conventional approaches. buildings faster, more a"ordably, and with more design freedom. It has expanded the footprint of Icon’s printing capability to 3D-printed homes for families in Mexico approximately 2,000 square feet. It has an adjustable width (to accommodate di"erent slab sizes) and is transported in Icon’s Icon is currently underway delivering resilient, dignified 3D custom trailer with no assembly required. The Vulcan II features printed homes in Mexico alongside nonprofit partner, New intuitive tablet-based controls, remote monitoring and support, Story. The resilient, 500 sq " homes were each 3D printed in onboard LED lighting for printing at night or during low-light con- around 24 hours of print time across several days, and feature ditions, and a custom so#ware suite ensuring set-up, operations, final construction build out by Échale, New Story’s nonprofit and maintenance are as simple and straightforward as possible. partner in Mexico.

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Located in Tabasco, Mexico, the homes will be granted to local families currently living in extreme poverty and makeshi!, unsafe shelter.

The resilient, 500 sq ! homes for families in Mexico were each 3D printed using Icon’s robotics, so!ware and advanced material. © JoshuaPerez

The built-to-last homes located in Tabasco, Mexico will be Through partnership with the local government, the 3D print- granted to local families currently living in extreme poverty and ed community is to be part of a larger community plan for the makeshi", unsafe shelter. The community of 3D-printed homes overall municipal area. The families will have access to green will contain 50 homes in total. spaces, parks, community amenities, and basic utilities through this master plan provided by the local government. The 3D printed homes feature two bedrooms, a living room, kitchen and bath. Co-designed with feedback from the families who will live in them, the homes have been created to meet the specific needs of the community. Resting within a seismic zone, the community and its homes were engineered above the standard safety requirements including robust foundations to www.iconbuild.com ensure the homes will last for generations.

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7_cpt_2002_60-69_Projects.indd 63 07.05.20 15:58 PROJECTS Concrete Pen Utility model registered by worldwide !D PRINTED ISOLATION HOUSES Case studies

In the face of the Corona epidemic, Yingchuang Build- 3D printed intelligent temperature ing Technique (Shanghai) CO., LTD. (Winsun) donated 3D measuring disinfection bus stop printed, smart isolation houses to designated hospitals The 3D printed intelligent temperature measuring disinfection to relieve the medical pressure and assist with e!ective bus stop, derived from the Winsun 3D printed smart bus stop, crisis management. has a zero-discharge public toilet and epidemic prevention products selling area, and it is also equipped with face recogni- To fight against the current epidemic, following a month of tion, temperature measurement, spray disinfection, ultravio- innovation, research and development, Winsun launched let sterilization, and alarm activation. If the temperature meas- [ personalization] 3D printed anti-epidemic prefabricated buildings, including ured is abnormal, the alarm will be activated, thus reducing smart temperature measuring disinfection checkpoints, in- the risk of infection. With application of big data technology, telligent temperature measuring disinfection bus stops, and health records of citizens can be established and monitored. negative pressure isolation houses. Each of the prefabricated buildings is integrated into one single unit and can be put into 3D printed isolation house operation a"er hoisting. The Winsun 3D printed isolation house is designed and manufactured in accordance with novel Corona virus isolation 3D printed smart temperature measuring disinfection check requirements. It is equipped with a negative pressure device, The 3D printed smart temperature measuring disinfection monitoring facilities, temperature measurement, ultraviolet check is applicable to densely populated areas, such as hos- sterilization, air purification, and other AI (artificial intelli- pitals, communities, o!ice buildings, supermarkets, schools, gence) devices. Therefore, the situation of isolated patients and heavy-tra!ic areas. It is equipped with several features, can be monitored in real time, and the information can be including face recognition, attendance management, tem- fed back to the attending physician. This saves time in the perature measurement, spray disinfection, ultraviolet sterili- medical treatment of patients. The individual isolation house zation, and alarm activation, all of which work in a safe, e!ec- is suitable for home isolation and medical sta! resting facili- » tive and intelligent way. Therefore, the unit can significantly ties. Multiple isolation houses can be connected to form larg- New design reduce the risk of infection of sta! who work on the frontline er units, which for example may be required in hospitals and » of the fight against the Corona virus. other medical facilities. Enhanced surface quality » Personalization now possible in precise color printing Discover the new Discover Pen! Concrete

[design]

3D printed disinfection check units 3D printed isolation house

[surface]

www.winsun3d.com

3D printed bus stop

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7_cpt_2002_60-69_Projects.indd 64 07.05.20 15:58 ConcretePROJECTS Pen Utility model registered by worldwide Discover the new Concrete Pen! » New design » Enhanced surface quality » Personalization now possible in precise color printing

www.concretepenfactory.com

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7_cpt_2002_60-69_Projects.indd 65 08.05.20 11:49 PROJECTS

LIVE !D CONSTRUCTION PRINTING OF A SMALL HOUSE In front of thousands of visitors

During the international Bautec construction exhibition in Berlin with over 30.000 visitors from more than 40 countries Cobod and Peri demonstrated the productivity of the Bod2 3D construction printer from Cobod by live 3D printing 64 m" of walls of a small house every day of the show. Each day visitors could live witness the Bod2 3D construction printer create the walls of a small house. The demonstration showed the way towards printing the walls of a normal size house in less than 24 hours.

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Peri and Cobod documented the live demonstration at Bautec. Watch video here:

3D rendering of the small house Cobod was printing every day at the Bautec.

Henrik Lund-Nielsen, CEO of Cobod explained: “With this showcase of live 3D construction printing we wanted to demonstrate, that our Bod2 printer technology is ready for the market, as it has the quality, speed, robustness and stability to perform hour a"er hour, day a"er day and with incredible productivity beating the conventional construction methods. We set out to print 4 small houses in 4 days and we achieved almost that. Each of the first 3 days we printed a small house, but the last day on request of the exhibition we chose to print a couple of their logos in large scale and consequently could only print half a house”.

Cobod and Peri, Cobod’s German shareholder and distributor, brought a Bod2 3D construction printer to the stand and performed live 3D construction printing of a small house.

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7_cpt_2002_60-69_Projects.indd 67 07.05.20 16:02 PROJECTS

Huge interest for taking videos and photos of the live 3D construction printing at Bautec.

The Bod2 printer from Cobod has a modular build and can Tilmann Auch, Cobod product development engineer, com- be extended in any direction with modules of 2,5 m, to a mented: “We would of course have liked to bring an even big- maximum of 15 m in the width and 10 m in the height. In the ger 3D construction printer, but printing live during the exhi- length the printer can be as long as desired. For Bautec Cobod bition meant some limitations. Consequently, we could only brought a relatively small Bod2 printer measuring 5 x 5 x 5m, print a very small one-bedroom house of approx. 4 x 4 m. Also, smaller than any of the seven Bod2 printers, that Cobod has as for speed, we have had to restrict ourselves. During Bautec sold since the Bod2 began shipping in January last year. The we only printed with 25 cm/s. This is due to the EU machine Bod2 could print with a speed of 100 cm/s, but materials and and robotics directive, which requires a safety fence around pumping equipment limitations have meant that the maxi- the printer, if we were to print faster. We surely did not want to mum speed so far has been 40 cm/s. put a fence up at the exhibition, as it would block the visitors’ possibility to see the printer in action too much. “

Even with the relatively limited speed of 25 cm/s, Cobod and Peri managed daily to 3D print a house with approx. 64 m# of walls in total, during the 8 hours opening time of the exhibition. Dr. Fabian Meyer-Brötz, head of 3D printing at Peri Group commented: “During Bautec we proved in front of all visitors, that we with a minimal crew could 3D print an average of 8 m# of walls per hour, and the walls were not even straight, as a good deal of them were curvy. It is important to note that these freeform capabilities are not only relevant for architectural purposes but allow for the integration of functionality in the walls and hence enable smarter building designs. We are not aware of any other technology, which can produce Product development such results. This is why we from Peri believe this technolo- engineer Tilmann Auch, gy is ready for the market, and we are pleased to bring it to Cobod, supervising the live the German speaking countries of Europe and continue the 3D printing at Bautec. development in partnership with Cobod.”

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7_cpt_2002_60-69_Projects.indd 68 07.05.20 16:03 New extrusion system in the printhead leading to much smoother printing.

Cobod and Peri are very keen on not just em- phasizing the freeform possibilities of 3D construction printing, but always also focus on the competitiveness of the technology in terms of productivity and labor cost. Henrik Lund-Niels- en explained: “Overall we managed what we set out to do and the results speak for themselves: With our technology our customers will be significantly more productive than users with conventional construction equipment and methods. Although we had to lower the speed in the exhibition area, we still managed to print 8 m# per hour. Going forward we aim to reach 20 m# of walls per hour by printing with 40 cm/s and use more powerful pumps. With such productivity the walls of a building with a floor plan of 150 m# could be printed in less than 24 hours. Fabian Meyer-Brötz, head of 3D printing at Peri, and his team showcasing No other technology can produce such results”. the end result for the printing on February 19, 2020.

COBOD International A/S PERI GmbH Dr. Tvaergade 26 Rudolf-Diesel-Strasse 19 1302 Copenhagen K, Denmark 89264 Weissenhorn, Germany T +45 70 605533 T +49 7309 9500 [email protected] [email protected] www.cobod.com www.peri.com

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7_cpt_2002_60-69_Projects.indd 69 07.05.20 16:05 INPRINT

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ICCX SPECIAL NEWS CONCRETE PRODUCTSCONCRETE PIPES AND MANHOLES PRECAST CONCRETE ELEMENTSREADYMIX Publishing Company: CONCRETE CPI worldwide is the only trade jour- ad-media GmbH nal for the concrete industry that is Industriestr. 180 · 50999 Cologne · Germany published worldwide in more than 10 T +49 2236 962390 · F +49 2236 962396 language and regional editions. CPI [email protected] · www.ad-media.de worldwide is addressing the decision www.cpt-worldwide.com makers in this industry. Every issue of CPI worldwide refers to concrete ORIGINALS ARE IDEAS THAT SET technology, concrete products, con- INDUSTRY STANDARDS. 3D molds by RATEC – Custom-Made Precision crete pipes and precast concrete. Printed in Germany www.ratec.org www.cpi-worldwide.com 2nd year of publication ©2019 by ad-media GmbH AZ_BWI_2020_3D-Schalung_Titel_181x218_EN_DE_01.indd 1 30.04.20 11:14 A CPI WORLDWIDE publication

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Autoclaved Aerated Concrete AAC worldwide is the only international trade WORLDWIDE All Rights reserved. No part of this publication may be reproduced, stored in a re trieval system, or transmitted www.aac-worldwide.com News & Markets EAACA launched new website Science & Innovation Wettability, dispersion and demand for surfactants journal for the autoclaved aerated concrete and their in! uence on the preparation of aluminium powder suspension in water Production Technology Complex upgrades made easy: A holistic approach for enhanced capacity Application & Construction “Renovation wave” – a chance in any form or by any means, electronic, mechanical, photo copying, recording or otherwise, without the prior for autoclaved aerated concrete Projects Strategies for more living space industry (AAC-industry). Each issue covers the permission of the copyright owner. Authors who submit texts and/or pictorial material („material“) for publi- For more reasons to choose for the Aircrete ﬂat-cake cutting technology, please visit: www. WHY TILT? entire spectrum of the industry – from trends cation grant ad-media the non-exclusive right, unlimited in time and territory, to publish the material. This JUST KEEP IT FLAT! applies to the media published by ad-media as well as to international trade publications in which employees and news from the world´s individual mar- AIRCRETE FLAT-CAKE SYSTEM FOR: • LESS HANDLING = LESS WASTE • NO STICKING AND NO SEPARATION kets to the latest developments in research of ad-media collaborate, and includes both the printed and online sector, including mobile applications for • SUPER SMOOTH SURFACES

aircrete • THIN PANEL PRODUCTION

smartphones, etc. The authors guarantee that they possess all rights to the material submitted that are nec- .com and science, state-of-the-art in the production essary for the aforementioned granting of rights to ad-media. The authors indemnify ad-media against all of AAC, building material applications and claims asserted by third parties on account of usage of the material in accordance with these general terms construction solutions and last but not least, and conditions. ad-media accepts no liability for the correctness of the contents of the material submitted by interesting buildings from all over the world. the authors. All views expressed in this journal are those of the respective contributors and are not neccesarily the opinions of the publisher, neither do the publishers endorse any of the claims made in the advertisements. www.aac-worldwide.com 2002_aac_c1-4_en.indd 1 26.03.20 11:08

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