Chapter Title: Industrialising Concrete 3D Printing: Three Case Studies

Chapter Author(s): Nadja Gaudillière, Justin Dirrenberger, Romain Duballet, Charles

Bouyssou, Alban Mallet, Philippe Roux and Mahriz Zakeri

Book Title: Design Transactions

Book Subtitle: Rethinking Information Modelling for a New Material Age

Book Editor(s): Bob Sheil, Mette Ramsgaard Thomsen, Martin Tamke, Sean Hanna

Published by: UCL Press. (2020)

Stable URL: https://www.jstor.org/stable/j.ctv13xprf6.31

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# Industrialising Concrete
3D Printing: Three Case Studies

**Nadja Gaudillière**

XtreeE, Rungis and Laboratoire GSA, École Nationale Supérieure d'Architecture Paris

**Justin Dirrenberger**

XtreeE, Rungis and Laboratoire PIMM, Arts et Métiers-ParisTech

**Romain Duballet**

XtreeE, Rungis and Laboratoire Navier, Champs-sur-Marne

**Charles Bouyssou, Alban Mallet, Philippe Roux and Mahriz Zakeri**

XtreeE, Rungis

## Introduction

Experimentation with 3D-printed concrete in architecture has flourished over the past decade and, consequently, so too has the development of industrial-grade manufacturing processes. 3D printing is part of a wave of robotic construction technologies developed with the 'digital turn' in architecture (Carpo, 2012) and, with it, the exploration of the possibilities offered by digital fabrication tools (Gramazio et al., 2015). Robotic technologies for construction sites have been designed since since the mid-20th century, but essentially consisted in the beginning of specialised machines accomplishing a single, repetitive task. Recent research has focused on more versatile machines, such as six-axis robotic arms, to perform a great diversity of tasks. This new approach to robotic construction processes, as well as the 'digital and informational turn' accompanying it, makes way for a potentially drastic renewal of the construction industry and its methods.

The introduction of these new robotic manufacturing technologies into the construction industry is still in the early stages, with numerous challenges needing to be overcome to reach full integration. These challenges must be studied in light of the potentialities of concrete 3D printing and other robotic fabrication processes, to ensure implementation in the construction industry in the most relevant way.

This paper gives a brief analysis of the current advancement of concrete 3D-printing technologies and the challenges facing researchers and companies, alongside three case studies of applications of concrete 3D printing developed by XtreeE. These applications have been developed in partnership with various significant players in the French construction industry,

<footnote n="1">1. 3D printing the artificial reef.</footnote>
<figure><img src="image_3.png" /></figure>

and have led to the manufacturing of several products as part of completed construction projects. Given the practical dimension of these case studies, they provide complementary information to academic research that can be used for further reflection on the industrialisation of such technologies.

## Current Advancements in Concrete 3D-Printing Processes

### Practical Aspects

The first manufacturing systems developed for concrete 3D printing – by precursors such as J. Pegna (Pegna, 1997); Contour Crafting (Khoshnevis, 2004); Loughborough University (Buswell et al., 2007); and D-Shape (Cesaretti et al., 2014) – are based on a variety of manufacturing systems, for both the printing nozzle and the motion system. A review of the various 3D-printing manufacturing systems developed so far can be found in Duballet et al., 2017.

Although the technologies discussed in this paper are often referred to as ‘concrete 3D printing’, a more accurate description is ‘cementitious materials 3D printing’. The development of various cementitious material formulations has accompanied the development of the first 3D-printing manufacturing systems, with each research group developing a specific formulation tailored to its needs and system characteristics. In recent years,

as cement manufacturers have become interested in the topic, several ready-to-use 3D concrete printing (3DCP) mixes have been developed and are now marketed. Various 3DCP mixes are available, but the materials used all have the same general rheological properties. A review of existing mixes and rheological properties can be found in Roussel (2018) and Buswell et al. (2018).

With the development of 3DCP manufacturing systems and adequate mixes, numerous applications have also been studied and developed. 3D printing has been experimented with at the scale of large buildings and architectonic elements, such as columns, stairs and floors (Gaudillière et al., 2018 and Rippmann et al., 2017). Products developed vary in use, including items for public works, indoor and urban furniture, and building components, amongst others. Research has focused both on product design and new structural possibilities. A detailed review of possible building systems and of existing prototypes can be found in Duballet et al., 2017.

### Challenges

Prototypes and projects built over the past few years have demonstrated both the viability and potential of 3DCP technologies. Several of these examples have been built by 3D-printing companies in partnership with both cement manufacturers and construction companies, demonstrating the active interest of the construction industry in these
processes. Nevertheless, both ongoing and published research on 3DCP processes and the conditions of production of projects points to challenges that must be tackled for industrial-grade 3DCP to fully mature and develop.

Beyond existing technical challenges, a review of which can be found in Buswell et al., 2018, the issues still to be confronted are, in the main, linked to long-established habits in the construction industry and the inertia that can be encountered in large industries. Despite the pervasion of new technologies, most of these digital tools have been adopted for the design stage and management of building sites. The ‘digital turn’ is based on the notion of ‘non-standard production’ (Cache, 1998), whereas the construction industry relies on ‘standard production’. A major paradigmatic shift must, therefore, happen for robotic construction processes to be fully adopted. While this change is under way – as the construction industry is, in part, divided up into many small business structures – it has not yet been fully assimilated. Furthermore, this evolution must be accompanied by the creation of new (currently non-existent) regulations, particularly for 3DCP. Such regulations will facilitate the adoption of digital technologies by all stakeholders in the industry, including insurance providers.

Where existing research has demonstrated the usefulness of 3DCP in areas such as material savings (Rippmann et al., 2017 and Duballet et al., 2018) and its potential to reduce the environmental cost of building methods, the assessment of the impact of robotic technologies remains a major challenge. Confronting these challenges will enable 3DCP potentials to blossom. Industrial developments by prominent companies hint at the potential for greater productivity in the construction

industry, which has been a notoriously problematic issue in recent decades. Finally, beyond the possibility of dealing with current construction and environmental challenges, experimenting with the use of 3D printing in architectural design could lead to the development of new formal and structural languages in the discipline.

## XtreeE Case Studies

### The XtreeE Printing System

The printing system developed by XtreeE, with which the case studies presented in this chapter were produced, is composed of four distinct parts: a computer supervising the 3D model and toolpath; a mixing unit for the 3DCP mix; a monitoring system for the dosage of the mix and additives; and the printing head developed by XtreeE, mounted on a six-axis robotic arm. Further details on the process and system can be found in Gosselin et al., 2016.

### Maritime Engineering: Artificial Reef

The first case study focuses on design and fabrication methods employed by a multidisciplinary team, involving architects, additive manufacturing specialists, generative designers and marine engineers to produce a 1m³ artificial reef, shown in fig.2. In February 2018, the reef was immersed in the Calanques National Park in France, as part of the REXCOR research project. The aim of REXCOR is the restoration of the rocky shoals of the Cortiou cove, into which Marseille city sewage has been discharged since 1896, impacting on the marine environment.

With the aim of restoring a lost ecological habitat, this biomimetic, porous reef mimics one of the richest environments in the Mediterranean Sea,

<figure><img src="image_4.png" /><figcaption>2. The artificial reef just after immersion.</figcaption></figure>

<caption>3. Stormwater collector installation.</caption>
<figure><img src="image_5.png" /></figure>

the Corallogenous habitat. This marine habitat – made of a structurally complex and dense biogenic substrate – took hundreds of years to form and is known to be a shelter for thousands of species, including fish, crustacea, coral, algae, molluscs, etc. Artificial concrete reefs are traditionally produced by assembling concrete slabs, drastically reducing the complexity of the available shapes and, with it, marine life development. 3D printing allows for greater possibilities, enabling marine engineers to design complex, tailor-made reefs. It also allows for multiple-scale cavities, unachievable through other processes but critical to the redevelopment of marine life in the targeted area.

A specific design method for the reef was developed, with the printing system's constraints – including a maximal slope angle and the continuous flow of concrete – and the biomimetic constraints – originating from the targeted ecological habitat – in mind. The prototype was printed sideways and consisted of a continuous, intersecting sheet of concrete, which considered the constraints while maximising the diversity of sizes and shapes for the cavities. On this occasion, an innovative workflow had been implemented between the members of the team,

with their differing areas of expertise needing to be put together to create the final geometry of the reef.

Although the immersion of the artificial reef presented here is recent, with regard to marine colonisation, traces of adoption by several species from the area can already be observed, confirming the potential of 3DCP technologies for future ecological engineering and restoration projects.

## Public Works: Stormwater Collectors

The second case study is a series of 3D-printed stormwater collectors for the cities of Lille and Roubaix in France in 2017 and 2018 (fig.3). These collectors are part of a larger series of prototypes produced by XtreeE and installed onsite, addressing specific public works' needs. The idea for the collectors originated in a workshop that brought together public-works company Point.P TP and XtreeE to study the potentials of 3DCP. This series of prototypes and their use in real-life situations has underlined the potential of 3DCP in public works.

The first collector prototype was 3D printed and installed in partnership with Point.P TP, followed by three more, built according to the same manufacturing method. The first collector was designated to a part of
the subterranean water network, situated under a busy
road. The recourse to 3D printing enabled a drastic
reduction in onsite intervention – two days, instead of
the usual two weeks – thus reducing inconvenience and
traffic disruption. The initial design was improved upon
the following three collectors, with the development of a
lifting system that consumed less material. The device
developed for this was also used to protect the existing
subterranean grid made of ancient brick vaults. As these
were susceptible to damage by a standard intervention,
the use of 3D printing enabled a connection detail to be
manufactured that preserved the vaults, despite their
structural weakness.

These prototypes provided an opportunity to develop
a workflow integrating several design teams and building
sites. The collectors themselves represent an interesting
experiment that integrates 3D concrete printing into
standard industrial workflows and methods; for the
fabrication of the collectors, the team applied a mixed
manufacturing technique based on a cast and printed
reinforced concrete slab. Further description of the
project and the mixed manufacturing technique can
be found in Gaudillière et al., 2019a.

Architectonic Elements: Freeform Truss Pillar

The production of architectonic elements raises many
issues regarding 3DCP processes. Several research
teams and companies are developing technologies
with the goal of increasing the scale of the printing area,
in order to produce increasingly larger buildings in a
single print. Others favour prefabrication, often onsite,
as is the case in the pillar presented here. Although
advocates of the use of 3D printing in construction often
highlight the idea that it could lead to the disappearance
of connections for building parts, this may be a
questionable outlook. The development of combinations
of 3DCP and other manufacturing methods appears
to be essential for assimilation into the construction
industry, whereas advocating for continuous, very
large-scale 3D printing might prevent this. Developing
smaller-scale architectonic elements, therefore, is
perhaps the optimal way to mix methods, both for the
fabrication of the elements and buildings themselves.

The pillar (fig.4) is a 4m-high column, made
of an integrated 3D-printed formwork filled with cast
concrete. The decision to cast concrete was made
following the absence of regulations for 3DCP in
construction at the time. This resulted, as shown
in Table 1, in an augmentation of the amount of
matter used in the pillar. A detailed description of
the manufacturing method is available in Gaudillière
et al., 2018, and in Buswell et al., 2018. The workflow
was similar to those in building projects and was,
therefore, much more linear. The decision to resort
to 3D printing was made much later than in the two
other case studies presented here.

<figure><img src="image_6.png" /><figcaption>4, Krypton Pillar, Aix-en-Provence.
Photo © Lisa Ricciotti.</figcaption></figure>
<table><caption>Table 1. Production time and matter consumption for projects in comparison to traditional production methods.</caption><thead><tr><td>Project</td><td>Production Time (%)</td><td>Material Consumption (%)</td></tr></thead><tbody><tr><td>Artificial Reef</td><td>33</td><td>33</td></tr><tr><td>Collectors</td><td>66</td><td>33</td></tr><tr><td>Pillar</td><td>21.6</td><td>-29</td></tr><tr><td>Urban Furniture</td><td>62.5</td><td>59.2</td></tr><tr><td>Average</td><td>45.8</td><td>24.05</td></tr></tbody></table>

## Production Times and Material Consumption

A study has been conducted to compare production time and material consumption for 3D-printed objects and for traditionally-built equivalents. Objects compared include the three case studies presented in this chapter, as well as prototypes for urban furniture. Details can be found in Gaudillière et al., 2019b, while results are given in Table 1.

## Conclusion

This paper presents three projects developed by the company XtreeE, in different contexts, as well as information on the different participants involved, manufacturing techniques employed, production time and material consumption. Through the description of these three case studies, this paper attempts to relate the experience in the field to existing research and

challenges identified in the development of 3DCP, for a better understanding of possible industrialisation routes.

Case studies, such as the ones presented in this paper, highlight several important factors for the development of environmental design guidelines. Case studies stress the need for regulation and for a fine-tuned control of optimisation processes, accompanied by said design guidelines. The workflows presented here advocate for the combination of 3DCP to already pre-existing techniques and for close collaboration between traditional stakeholders and new players, prompted by the development of 3D printing.

By combining the expertise of stakeholders in the industry and the mastery of robotic technologies developed by researchers, such as 3DCP, design guidelines could be established that minimise the negative impact of construction activities. New levels of productivity and efficiency could be reached, alongside significant improvements in the quality of the built environment.
## Acknowledgements

The XtreeE team would like to thank the partners that have helped make the projects presented in this paper possible and that have contributed to them, including: Stormwater collectors: Point.P TP, La Sade. Artificial reef: Seaboost. Krypton pillar: EZCT Architecture & Design Research, Marc Dalibard Architecte, LafargeHolcim, Fehr Architectural, Artelia, AD Concept.

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