39th International Symposium on Automation and Robotics in Construction (ISARC 2022)

Requirements analysis of additive manufacturing for

concrete printing – A systematic review
Patricia Peralta-Abadia and Kay Smarsly

Institute of Digital and Autonomous Construction, Hamburg University of Technology, Germany

Email: patricia.peralta.abadia@tuhh.de, kay.smarsly@tuhh.de

Abstract – concrete components by successfully conducting

The acceptance of concrete printing as a viable manufacturing processes, expertise and a common
construction method is limited because of a lack of understanding of concrete printing are required [3]. The
expertise and due to the heterogeneous and non- acceptance of concrete printing as a viable construction
standardized nature of additive manufacturing (AM) method has been limited due to a lack of expertise and
data modeling, affecting the reliability and the understanding and because of the heterogeneous and
interoperability of the concrete printing process. To non-standardized approaches commonly deployed for
advance standardization of AM data modeling in AM data modeling, for material testing, and for
concrete printing, information exchange manufacturing, each of which affecting the reliability and
requirements must be defined along the digital thread, interoperability of the concrete printing process. New
i.e. the digital workflow that transforms 3D models data modeling approaches proposed for concrete printing,
into printed components. In this paper, a encompassing the digital workflow to transform 3D
requirements analysis of AM for concrete printing is models into printed components (i.e. digital thread), have
conducted through a systematic review. The AM to be developed to improve reliability and
process for concrete printing is defined, identifying interoperability. Synergies between conventional AM
information exchange requirements. Sources relevant methods and concrete printing can be exploited to
to AM and concrete printing are systematically formally describe AM data modeling for concrete
reviewed, collecting and analyzing attributes of the printing.
information exchange requirements for concrete In concrete printing, actors of heterogeneous domains
printing. As a result, the requirement analysis serves (e.g. design, engineering, material sciences, and machine
as basis to standardize the digital thread, in an operation) collaborate along the digital thread to
attempt to advance reliability and interoperability of transform the 3D models into printed components,
the concrete printing process. exchanging information to perform concrete printing
tasks and subprocesses. Information exchange
Keywords – requirements describe information of a task or
Additive manufacturing (AM), concrete printing, subprocess (i.e. a set of tasks) that are exchanged
data modeling, information exchange requirements, between the actors to enable downstream tasks or
requirement analysis subprocesses [4]. However, information exchange
requirements along the digital thread have not been
clearly defined, causing a loss of semantic information
1 Introduction and a lack of interoperability. Concepts of building
In the architecture, engineering, and construction information modeling may advantageously be used to aid
(AEC) industry, research has been conducted to automate the standardization of the information exchange
construction processes that are based on additive requirements, preserving semantic information and
manufacturing (AM). AM allows structures to be built in improving interoperability along the digital thread, while
a layer-by-layer basis, employing computer-controlled further advancing the acceptance of concrete printing as
processes [1]. Using printable concrete, large-scale a viable construction method.
building components have been manufactured by In this paper, a requirements analysis of AM for
deploying concrete-based AM processes, also referred to concrete printing is conducted through a systematic
as concrete printing [2]. In concrete printing, review. Information exchange requirements are defined,
interdependencies of the material and the manufacturing following the methodology developed for information
process affect the quality of manufacturing, thus the delivery manuals known widely used in building
quality of the printed components. To ensure high-quality information modeling, which documents processes and
 39th International Symposium on Automation and Robotics in Construction (ISARC 2022)

describes the corresponding information to be exchanged interoperability along the digital thread as well as data
between the actors [4]. The paper is organized as follows. collection and storage. For the sake of brevity, only the
First, the AM process for concrete printing is defined and consideration of the material interdependencies in the
the information exchange requirements are identified. semantics of AM design and optimization and of AM
Second, sources relevant to AM and concrete printing are process planning are reviewed in this paper. In the
systematically reviewed to collect attributes of the following section, the requirements of AM for concrete
information exchange requirements along the digital printing are reviewed and analyzed, focusing on AM
thread in concrete printing. The information exchange design and optimization as well as on AM process
requirements are analyzed, using AM design and planning as illustrative examples.
optimization as well as AM process planning as
illustrative examples. The paper concludes with a
summary and an outlook on potential future research. 3 Review and analysis of requirements of
additive manufacturing for concrete
printing
2 Additive manufacturing process for
concrete printing In this section, the systematic review and the analysis
of the requirements of AM for concrete printing are
An extract of the digital workflow for concrete presented. Due to the synergies between AM and
printing, from design to print, is represented as a process concrete printing, sources relevant to both areas are
map shown in Figure 1. A process can be nested, and it systematically reviewed. First, the systematic review of
may contain subprocesses. A process (as well as a the sources is provided. Then, the requirements analysis
subprocess) is a set of tasks that are interrelated or that according to completeness and interoperability is
interact with one another, transforming inputs into presented.
outputs. The process map shown in Figure 1 is based on
[5] and follows the business process modeling notation. 3.1 Systematic review
Four main actors participating in the workflow are
identified: designer, engineer, material scientist, and The review methodology comprises three steps, (i)
machine operator. The actors develop specific tasks source selection, (ii) data collection, and (iii) data
(differentiated by colors) or subprocesses, where the data organization. Sources, precisely standards, current
generated in the tasks or in the subprocesses is exchanged research (i.e. journal papers and conference papers) and
among the actors, following a sequence that translates 3D software applications, are selected for the review (Figure
models into printed objects. 2). The papers are indexed in the Web of Science Core
As can be seen from Figure 1, the AM process starts Collection, in the Scopus database, or in the American
with design concepts, from which design specifications Society of Mechanical Engineers digital collection. A
are defined. With the design specifications, geometric total of 30 sources relevant to AM and concrete printing
models are generated considering manufacturability, and have been selected. From the sources, attributes of the
manufacturing hardware is selected. Settings for the information exchange are collected and organized in
manufacturing hardware are defined to design the information units. In the following paragraphs, an
material (concrete) in an iterative process, until satisfying overview of the systematic review is presented.
the design specifications. Once the material is designed, Existing standards for AM define terminology, data
material specifications are generated. Then, the formats, and data models used to exchange information
geometric models are sliced and toolpaths are planned for geometric representation and for hardware control.
according to the process data and the material The standard terminology for AM technologies is defined
specifications. Within the subprocess of toolpath in the ASTM F2792 standard [1], categorizing AM
planning, simulations of the manufacturing process and technologies. There are three main data format standards
of the material are carried out. The subprocess of toolpath for geometry representation: standard tessellation
planning has AM models as outputs. Then, the AM language (STL), additive manufacturing format (AMF),
models are evaluated and, if accepted, the AM models are and 3D manufacturing format (3MF). The STL format is
used as basis to generate machine-readable code (CNC the de-facto standard in AM. An STL file is an unordered
code) that provides the instructions for manufacturing. collection of triangles, vertices, and unitary surface
Data modeling in concrete printing has synergies with normal vectors in binary or ASCII format [6]. AMF is an
the data modeling approaches used for conventional AM ASTM/ISO standard (ISO/ASTM 52915), which extends
methods. However, considerations regarding the STL to include dimensions, curved facets, recursive
interdependencies of the concrete and the manufacturing subdivision, color, material, constellation descriptions,
process are to be included in the information exchange and metadata.
requirements. A common data model will support
 39th International Symposium on Automation and Robotics in Construction (ISARC 2022)

Designer Engineer Material scientist Machine operator

Define
specifications
New Design Design
concrete concept specifi-
printing cations
project
X
Geometric Hardware
model specifications
Design Slice Specify
geometry geometry hardware
Process
data
Sliced Design Define
model material settings

Plan toolpath Material

specifications

AM
model
Approved?
No: No:
Change geometry Change process settings
\

Yes
Generate
CNC code

CNC
code

Printing information
model

Figure 1. Extract of the process map describing the AM process for concrete printing

AMF is based on extensible markup language (XML), associated machine hardware functions specified in the
providing an XML-based schema definition (XSD) for EXPRESS language [10].
AM technologies [7]. 3MF is an XML-based data format In the following paragraphs, current research in AM
that provides broad model information, such as mesh and concrete printing, published between 2015 and 2021,
topology, slices, color, material, and texture, allowing is organized according to the research topic. Table 1
multiple objects to be contained within a single archive presents an overview of the research topics and the
[8]. related references. Below, a brief overview per research
For hardware control, there are two main standards: topic is presented.
G-code and the STandard for the Exchange of Product Relevant to process and geometry parameters, the
model data compliant Numerical Control (STEP-NC). implementation of AM in the AEC industry has been
The ISO 6983 standard [9], also known as G-code, is reviewed in [2], while in [3] technical issues in concrete
widely used as a numerical control (NC) programming printing have been described. A framework to classify
language. G-code supports hardware control in AM process used in concrete printing has been defined in [11].
processes, defining motion and action commands in Process parameters and the impact on the manufacturing
sequential lines [6]. The STEP-NC extends the ISO process has been studied in [12]. Strategies to improve
10303 standard in ISO 14649 and defines a data model the control of the manufacturing process have been
for numerical controllers. STEP-NC provides control proposed by using sensing technologies [13] and by
structures for the sequence of working steps and simulating the manufacturing process to optimize process
 39th International Symposium on Automation and Robotics in Construction (ISARC 2022)

parameters [14]. The interactions between geometry BIM for data modeling. Using an open BIM standard,
parameters and process parameters, including the such as the Industry Foundation Classes (IFC), data can
manufacturing process, have been studied for concrete be managed and exchanged between software
printing [3] and for conventional AM methods [15]. applications used for AM and software applications used
in the AEC industry, maintaining semantic and geometric
information. Research has been conducted to couple
concrete printing and BIM, showing the potential of
BIM-based concrete printing, focusing on data retrieval
from BIM models [28] and on IFC-based descriptions of
process and material parameters [29].

Table 1 Overview of research topics related to AM and

concrete printing
Research topic Qty. of References
references
Figure 2. Categorization of sources according to type [2-3, 5-6, 11-
Process and geometry
18 16, 19-20, 23-
Material parameters and the interactions with the parameters
26, 28-29]
manufacturing process have been reviewed in [16]. [3, 12, 14, 16-
However, technical issues regarding material parameters Material parameters 12
22, 26,29]
are still open points, as discussed in [3]. Research Modeling and
regarding material parameters in concrete printing has 5 [18-22]
simulation
been focused mainly on material development [17], on AM-related
material testing for fresh concrete [18], and on the impact 7 [5-6,23-26,29]
ontologies
of the manufacturing process on material parameters [19].
Modeling and simulations in AM are used to simulate BIM-related research 6 [2,15,26-29]
and optimized the manufacturing process [20], analyze
the material [19], and to predict the structural stability of Software applications used to develop concrete
the printed components during manufacturing [14]. printing projects help determine the information
Numerical modeling and simulations have been used to generated in tasks along the digital thread (input and
predict the concrete flow to determine the optimal output parameters). Functionalities in the AM software
rheological requirements of the concrete [21]. Perrot et al. applications support AM design and optimization as well
[22] have discussed the implementation of analytical and as AM process planning. Software applications for AM
numerical tools to assess the concrete printing process as design and optimization are usually based on computer-
a function of the material properties, the geometry of the aided designs and enable geometry optimization.
components, and the process parameters (e.g. Software applications for AM process planning are
manufacturing hardware settings). commonly used for slicing and toolpath planning,
AM-related ontologies are formal descriptions of the creating manufacturing models. Complex AM software
field of AM (or subfields), where concepts and applications for AM process planning also support
relationships are defined. Ontologies contain the current simulations of the manufacturing process where the
knowledge in AM and can be extended to support future effect of toolpaths and hardware settings can be evaluated
knowledge. The semantics of AM technology have been to ensure buildability. The user manuals of common AM
defined based on STEP-NC [6]. Ontologies have been software applications, such as Cura slicer [30] and Slic3r
developed to support manufacturability analysis [23], [31], provide insight into the input and output parameters
interoperability for data management [24], and lifecycle needed for AM design and optimization and AM process
data management [25]. Similarly, ontologies have been planning.
developed specifically for the digital thread of metal- Due to the nature of concrete printing, vendors have
based AM [5] and for developing BIM-based concrete developed proprietary solutions for the manufacturing
printing [26]. hardware used for concrete printing (i) by modifying
BIM-related research in AM has been developed to existing AM software or (ii) by developing software tools.
integrate AM into the AEC industry. BIM concepts, In the first case, open-source and proprietary software
providing semantic and geometric information, have applications for slicing and toolpath planning have been
been used to digitalize life-cycle information of buildings modified to fit specific manufacturing hardware used for
and infrastructure. Paolini et al. [2] as well as Gradeci et concrete printing. In the latter case, computer-aided
al. [27] have discussed the benefits of coupling AM and design software applications have been coupled with
 39th International Symposium on Automation and Robotics in Construction (ISARC 2022)

programming environments to develop specialized component. Interoperability is supported when the

software tools for concrete printing. Moreover, semantics of the information exchange requirements are
simulation software applications commonly used in the preserved when transitioning between actors and tasks.
AEC industry have been used to conduct simulations of Hence, satisfying completeness and interoperability of
the manufacturing process and of the material behavior the information exchange requirements provides a strong
to predict the structural performance of printed basis for a common understanding between actors,
components, as shown in [18]. enhancing the reliability of concrete printing. The
To streamline the digital thread in concrete printing, information exchange requirements are discussed in the
attributes of the information exchange requirements are following paragraphs, focusing on AM design and
collected and organized into information units from optimization as well as on AM process planning for
standards, current research and software applications. In illustration purposes.
the following subsection, the requirement analysis In AM design and optimization, geometric models are
relevant to AM design and optimization as well as AM generated from conceptual designs. The main
process planning is presented. information exchange requirements are design concepts
and design specifications (Table 2). The design concepts
3.2 Requirements analysis include the geometry pre-design and information
regarding material, print location, structural
From the previous review, the attributes of the characteristics, and structural boundary conditions. From
information exchange requirements have been collected the design concepts, design specifications are defined
in the following tables and organized into information regarding AM process, material requirements, geometric
units. The attributes are analyzed according to tolerances and geometric requirements. As output,
completeness (i.e. if an attribute is required or optional) geometrical models (e.g. BIM models) are generated
and interoperability. The attributes have been discussed according to design and hardware specifications and can
with experienced users from the domains of robotics, be further be optimized with respect to manufacturability,
material science, civil engineering, and mechanical topology, structural performance, and geometric
engineering. tolerances. In Table 2, prerequisites of the information
Completeness of the information exchange exchange requirements for design specifications are
requirements avoids redundancies and ensures the highlighted in gray.
inclusion of all attributes necessary to manufacture a

Table 2 Information exchange requirements for design specifications

Type of information Information needed Rqd. Opt.
The design concept will have been carried out prior to define the basic
Design concept
requirements
Requirements for the AM process
 AM process type X
AM process
 Machine type X
 Reinforcement type X
Requirements for the materials according to the AM process
requirements.
 Main material selection (e.g. reinforced high-performance concrete) X
Material requirements
 Support material selection (e.g. plaster) X
 Reinforcement material selection (e.g. carbon fibers) X
 Main material minimum strength (e.g. 30 MPa) X
Allowed tolerances in the geometric precision of the printed
component/structure
Geometric tolerances  Deformation under self-weight X
 Deflection under self-weight X
 Allowed shrinkage X
Requirements for the geometric details according to the AM process
Geometric requirements (e.g. machine type) and materials requirements
 Maximum overhang angle X
 Minimum feature size X
 39th International Symposium on Automation and Robotics in Construction (ISARC 2022)

Table 3 Information exchange requirements for process data

Information unit Attributes Rqd. Opt.
The basic requirements will have been carried out prior to defining the
Basic requirements
process data
The hardware specifications will have been carried out prior to
Hardware specifications
defining the process data
Feedback data Feedback from previous manufacturing processes
Printing strategy for the AM process
 Layer-by-layer strategy X
 Layer transition type X
 Infill pattern X
Strategy
 Infill density X
 Boundary thickness (i.e. number of adjacent filaments) X
 Layer interval time X
 Nozzle height above previous layer X
Boundary conditions of the AM process
 Environment temperature X
Boundary conditions
 Environment humidity X
 Machine boundary conditions (e.g. printing area and flow rate) X
Machine parameters for the AM process
 Printing speed X
Machine parameters  Traveling speed (i.e. speed when not extruding) X
 Acceleration X
 Pump pressure X

In AM process planning, the geometrical models are systematic review and discussion with experienced users.
sliced and the toolpaths are planned. The geometrical In conclusion, the information exchange requirements for
models and design specifications, together with hardware concrete printing show synergies with the information
specifications, process data and material specifications, exchange requirements of conventional AM methods. In
provide the basic information necessary for process particular for concrete printing, the hardening process of
planning. The effect of the manufacturing process on the concrete has a non-negligible effect on the process
material properties and on the behavior of concrete must parameters (e.g. manufacturing hardware settings, print
be considered when defining the material specifications, strategy) and on planning and control of the
hence the process data and the material design are manufacturing process. Therefore, the interdependencies
adjusted in an iterative process to satisfy the design of the concrete and the manufacturing process have to be
specifications. As an output, AM models are created considered along the digital thread when advancing
containing all the information necessary to generate reliability and interoperability of the concrete printing
machine-readable code (CNC code). process. For illustration purposes, AM design and
Table 3 and Table 4 present the information exchange optimization and AM process planning have been
requirements for process data and material specifications, analyzed in detail, identifying the material-related
where prerequisites are highlighted in gray. information exchange requirements necessary for
concrete printing.
With the information exchange requirements clearly
4 Summary and conclusions defined, the digital thread can be described as a formal
In this study, efforts towards standardizing AM data data model. With the data model, collaboration between
modeling have been presented, and information actors will be enhanced resulting in a smooth workflow
exchange requirements in AM have been analyzed in the to improve the quality of the manufacturing process and
context of concrete printing. The AM process for the printed components. There is still a need to develop
concrete printing has been defined, and information data models that support the digital thread in concrete
exchange requirements have been identified. Attributes printing in compliance with current standards used to
within information exchange requirements for concrete digitalize the AEC industry, such as open BIM standards.
printing have been collected and analyzed through a
 39th International Symposium on Automation and Robotics in Construction (ISARC 2022)

Table 4 Information exchange requirements for material specifications

Information unit Attributes Rqd. Opt.
The hardware specifications will have been carried out prior to
Hardware specifications
defining the material specifications
The process data will have been carried out prior to defining the
Process data
material specifications
Material specifications for the main material to be employed in the
AM process. Parameters may vary depending on the material
 Concrete type (e.g. C35/45) X
 Design strength X
Main material design  Maximum aggregate size requirement X
specifications (e.g.  Slump requirement X
Concrete)  Design open time X
 Estimated volume X
 Batching type X
 Pre-process treatment (e.g. contact surface preparation) X
 Post-process treatment (e.g. surface cover and surface uncovered) X
Support material design Material specifications for the support material to be employed in the X
specifications AM process. Parameters may vary depending on the material
Reinforcement material Material specifications for the reinforcement material to be employed X
design specifications in the AM process. Parameters may vary depending on the material

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