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CPT
worldwide
CONSTRUCTION
PRINTING
TECHNOLOGY
2.2020
www.cpt-worldwide.com
MEDIA PARTNER
GREEN WAY TO 3D PRINT
3D PRINTED CUSTOM BLOCK PAVEMENT AND OBJECTS
INDUSTRIAL CONCRETE PRINTING SOFTWARE
3D PRINTED STAIR MOLDS
3D printed homes
for homeless in Austin
page
Bedroom, bath, kitchen,
living room and large porch 60
© www.iconbuild.com
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 affecting 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 difficult 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 tech-
nical innovation, attracts an increasing international attention, and paves the path into the future of con-
struction and manufacturing methods. On all continents, experts are dedicating their professional efforts
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 construc-
tion 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 Crafting belongs to the pioneers of concrete printing and we are pleased to pres-
ent 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 difficult 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 editor@cpt-worldwide.com
Dipl.-Ing. Mark Küppers, editor in chief
2.20 | 3
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CONTENT
6
66
32
44
54
2.20
1_cpt_2002_03-05_Edi.indd 4 08.05.20 11:58
CONTENT
NEWS
6 Contour Crafting 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 software
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 Crafting: 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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1_cpt_2002_03-05_Edi.indd 5 08.05.20 11:58
NEWS
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 Crafting technology in addressing the homelessness problem
County Development Authority (LACDA) has awarded in Los Angeles and worldwide. The freedom in the architectur-
Contour Crafting Corporation (CC Corp) a project on using al design and high degree of customization which is possible
construction 3D printing for affordable 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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2_cpt_2002_06-13_News.indd 6 07.05.20 14:05
NEWS
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 different 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 tradi-
tional concrete which has been used for decades.
The third advantage of inclusion of large aggregates in Contour Crafting 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 CO2. Inclusion of gravel in the print- www.contourcrafting.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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NEWS
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 shift to the predominantly manual construction
and more efficient, resource-saving construction meth- techniques, which promote simple element forms and ineffi-
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 Kloft 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 CO2 emissions, this novel
Research Centres to strengthen cutting-edge research at technology will provide an efficient 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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NEWS
Professor Anke Kaysser-Pyzalla, President of the TU Braun-
schweig. “I am proud of the team effort 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 engineer-
ing 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 of TRR277.
Credit: ITE
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 digitaliza-
tion of the construction industry, with increased productivity
and an efficient use of resources.
Technische Universität Braunschweig
Collaborative Research Centres and Transregional Projects Institute of Structural Design (ITE)
Prof. Dr.-Ing. Harald Kloft
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 effort and are thus intended to serve as focal points h.kloft@tu-braunschweig.de
and structures for the applicant universities. ite.tu-braunschweig.de
DIGITAL CONCRETE 2020
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 differ- 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 confer-
ence, in the same week as originally planned, starting on
July 6. Over the course of 4 days, there will be online ses-
sions 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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NEWS
3D CONCRETE PRINTING
AND OTHER DIGITAL CONCRETE
CONSTRUCTION TECHNOLOGIES
2nd German Industry Seminar, October 28th, 2020, Dresden, Germany
3D concrete printing is particularly suitable both for dig- The seminar offers 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 auto-
mation of relevant production processes constitute the The event venue is the Alte Mensa Event Hall (“Dülfersaal“,
most promising approach to introducing urgently needed 1st 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.
After the successful start last year, the 2nd 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 com-
prehensive overview of the most important developments,
which will be scrutinized critically and impartially. The sem-
inar 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 Baustoffe
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.baustoffe@tu-dresden.de
10 | 2.20
2_cpt_2002_06-13_News.indd 10 07.05.20 14:05NEWS
ACCIONA LAUNCHES GLOBAL
3D 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 efficien- 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 offers 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 in-
ternal 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 print-
ing, 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 XL 3D Printing
market.
www.vertico.xyz
As an experienced player in the concrete printing market, Ver-
tico has the know-how to provide turn-key, full service con-
crete 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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2_cpt_2002_06-13_News.indd 11 07.05.20 14:05NEWS
EXCLUSIVELY
DESIGNED
FURNITURE
More than just an eye catcher
3D concrete provides creative oppor-
tunities for architects and planning
agencies. The Austrian enterprise 3D
Betondruck Solutions has been a pio-
neer in this innovative technology.
Based on intense development efforts
unique solutions for indoor and outdoor
use, such as exclusively designed furni-
ture can be realized. Possible re-use as
recycled granulate guarantees sustain-
ability. Different surfaces and colouring
of the concrete set individual accents.
www.3dbetondrucksolutions.at
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2.20 | 13
2_cpt_2002_06-13_News.indd 13 07.05.20 14:05RESEARCH & DEVELOPMENT
CONPRINT3D
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 solu-
tion 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 ZukunftBau 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. Affairs 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 offers 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; often 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 con-
crete 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-efficient, 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:
14 | 2.20
3_cpt_2002_14-31_Research_Development.indd 14 07.05.20 14:48Figure 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.
He is Coordinator of the German
CONPrint3D is developed for monolithic construction with sharp corners and pre-
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-
tion materials“ and Speaker of the
At present, concrete printers are expensive special machines. For reasons of econ-
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
of the Journals “Cement and Con-
pump for use as a 3D printer, see Figure 2.
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,
Chair of RILEM TC RSC-260 „Rec-
The development of new standards and their eventual implementation are tedious
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
German Committee for Reinforced
developed. In addition to ordinary and high-performance concrete, foam concrete
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
(ACI) and Innovation Award of the
tolerances according to existing standards
bauma 2016 Munich.
At present, printheads are in the main merely simple nozzles. Due to the lack of mechtcherine@tu-dresden.de
smoothing post-processing, on the one hand a “sausage look” is created which is
2.20 | 15
3_cpt_2002_14-31_Research_Development.indd 15 07.05.20 14:48RESEARCH & DEVELOPMENT
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-
tion of cement-based materials for
not always acceptable. On the other hand, total control of the material flow as well
extrusion-based 3D-printing” in as the precision of the material placement and its final shape are often insufficient
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.
He is a member of RILEM technical
scale filaments of defined geometrical shape and surface quality, while enabling
committee on “Digital fabrication manufacturing sharp corners as well as accurate endings and openings.
with cement-based materials”.
nerella@msx.tu-dresden.de 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 au-
thors 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 con-
cepts 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 different 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 different 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-
frank.will@tu-dresden.de
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.
16 | 2.20
3_cpt_2002_14-31_Research_Development.indd 16 07.05.20 14:48RESEARCH & DEVELOPMENT
1
2
3
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
of construction machinery and the
vestigation and modification of the boom drive in order to optimize the positioning 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
suitable for construction sites.
nents, control algorithms, and control systems can now be developed to reduce mathias.naether@tu-dresden.de
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 lay-
ers 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. After 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.
jens.otto@tu-dresden.de
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3_cpt_2002_14-31_Research_Development.indd 17 07.05.20 14:48RESEARCH & DEVELOPMENT
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 print-
head, special attention was given to a modular design. This allows, for example,
the use of different conveying mechanisms or the exchange and optimization of
particular components. As indicated above, the printhead can also be equipped
with different forming systems adjusted to the respective printing principle:
• Simple outlet nozzles with a fixed cross-section for production of test speci-
mens 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
martin.krause3@tu-dresden.de designing 3D-printable concretes in a performance-based approach. A comprehen-
sive 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
18 | 2.20
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www.tu-dresden.de
28th October 2020
1 Dresden, Germany
2
4
3
2 nd German
Figure 5: Printhead under development: (1) extruder and the complex
forming system with (2) nozzle, (3) shaping plates, (4) shutter and several
Industry
actuators for printing filaments with varied cross-section / walls with
varied thickness.
Seminar
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 pos-
sible 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)eq was 0.51, calculated in accordance with EN 206-1.
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 Bausto e
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 e@tu-dresden.de
2.20 | 19
The seminar language will be German.
3_cpt_2002_14-31_Research_Development.indd 19 07.05.20 14:48RESEARCH & DEVELOPMENT
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 differ-
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, stiff 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 after 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 m3/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 effect 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 affordable labor. But often the workers are
ing research using limestone calcined clay cements and novel not sufficiently 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 after 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 con-
struction 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 insufficient 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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3_cpt_2002_14-31_Research_Development.indd 21 07.05.20 14:48RESEARCH & DEVELOPMENT
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 Zukunft Bau of
anisotropy resulting primarily from the quality of the interlay- the Federal Institute for Research on Building, Urban Affairs
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 digiCON2 - 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: Effects 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 Offhighway 03 (2018) 46–51. [16] J. Otto, J. Kortmann, M. Krause: Wirtschaftliche Perspektiven von Be-
[6] S. Zorn, F. Will, P. Mögle: Control stabilization of multilink manipula- ton-3D-Druckverfahren. Beton- und Stahlbetonbau 115 (2020) Heft 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
3D 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, shifting 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 mon-
itoring, 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) character-
isation 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.
2.20 | 23
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