The document discusses additive manufacturing (AM) processes and applications in construction. It provides an overview of AM, including common processes like material extrusion and powder bed fusion. Examples of AM construction projects are described, such as a printed office building and hotel. Key challenges in applying AM to large-scale construction include developing suitable feedstock materials that can be extruded while maintaining appropriate properties. Cementitious materials are most commonly used and studies have found optimized mixes include cement, fly ash, silica fume and additives to achieve desired strength and printability.

1. ADDITIVE MANUFACTURING IN CONSTRUCTION
INDUSTRY: A REVIEW ON PROCESSES AND
APPLICATIONS
GUIDE
ABHAY RAJAN
ASSISTANT PROFESSOR
MECHANICAL ENGINEERING DEPARTMENT
PRESENTED BY
RAHUL R
S1 M TECH
ROLL NO: 13

2. ADDITIVE MANUFACTURING
 Additive manufacturing (AM) or additive layer manufacturing (ALM) is the industrial
production name for 3D printing, a computer controlled process that creates three
dimensional objects by depositing materials, usually in layers.
 AM is a rapidly growing field that is having an impact on multiple industries by simplifying
the process to go from a 3D model to a finished product.
 In contrast to conventional manufacturing processes, AM fabricates objects by adding
materials as required which eliminates the necessity of subtracting materials (by means of
machining, milling, carving, etc.) to obtain desired shapes.
 AM can advantageously fabricate complex geometries with no part-specific tooling and much
less waste material.
2

3.  The technology has been adopted in the manufacturing industry for decades.
 Aerospace, automotive, and healthcare industries have explored the benefits of using AM in
their businesses.
 Initial applications focused on rapid prototyping to reduce the time required to produce
prototypes with complex geometries.
 Since then, AM has evolved to include many types of functional end-use parts.
 In the recent COVID-19 situation, additive manufacturing (AM) became a supplementary
manufacturing process to meet the explosive demands for medical equipment such as
ventilators, nasopharyngeal swabs and PPE such as face masks and face shields.
3

4. ADDITIVE MANUFACTURING PROCESSES
 The American Society for Testing and Materials (ASTM) International published a document
in collaboration with the International Organization for Standardization (ISO) to define
standard terminology for AM.
 In that document, ISO/ASTM divided AM into seven different processes
1. Vat Photo polymerization – A process of selectively curing a liquid light-activated polymer
with a laser. An example of this process is stereo lithography apparatus (SLA).
2. Material Jetting – A process of selectively depositing drops of material in a layer wise
fashion. An example of this process is PolyJet technology from Stratasys.
4

5. 3. Binder Jetting – A process of depositing a powdered material layer upon layer and
selectively dropping a liquid binding agent onto each layer to bind the powders together.
4. Material Extrusion – A process of extruding material through a nozzle and depositing it
layer-by-layer onto a substrate.
5. Powder Bed Fusion – A process of selectively fusing a powder bed using thermal energy,
typically in the form of a laser or electron beam.
6. Sheet Lamination – A process of successively shaping and bonding sheets of material to
form an object. An example of sheet lamination process is laminated object manufacturing
(LOM).
7. Direct Energy Deposition – A process of fusing materials with focused thermal energy that
melts the material as it is being deposited. 5

6. 6
Fig.1 : Seven AM Processes according to ASTM

7. ADDITIVE MANUFACTURING & COVID 19 CHALLENGES
 Coronavirus disease 2019 (widely known as the COVID-19), which was first recognized in
December 2019 in the Wuhan city of China, had spread so fast that within a very short time it
was classified as a global pandemic.
 From the very outset of the COVID-19 pandemic, healthcare and personal protective
equipment (PPE) suppliers began to struggle to meet the acute demands of specific items such
as face masks, face shields, test kits, ventilators, etc.
 Global supply chains were disrupted as a result of reduced employees and lockdown in many
areas of the world, making the situation even more critical.
 AM was helpful in the production of items like face mask, face shield, ventilator parts and NP
swabs.
7

8.  Most of the parts manufactured by the 3D printing technology to meet the COVID-19
challenges were made of polymeric materials.
 Biocompatibility, non-toxicity, and disinfection procedures are some important criteria that
are considered during selecting the polymeric materials for producing the medical parts and
PPE applications.
 Major AM techniques used to print polymeric parts are
1. Stereo lithography apparatus (SLA)
2. MultiJet printing
3. Selective laser sintering (SLS)
4. Multi jet fusion (MJF)
5. Fused deposition modeling (FDM)
8

9. 9
Fig.2 : A flowchart showing the interrelations among various materials, AM techniques, and
major 3D printed products to face the COVID-19 pandemic challenges.

10. 10
Fig.3 : (a) An FDM-based printer creates frames of face shields, (b) a face shield with various components, e.g., frame/
headband, bracket, and visor, (c) 3D printed face shield from (b) with other PPE worn by an Intensive Care Consultant
Fig.4 : (a) Various components of the main structure of a 3D printed face mask, (b) AM creates ample opportunities
and customizations in the design of face masks, (c) a perfectly fit 3D printed face mask

11. 11
Fig.5 : (a) An additively manufactured ventilator valve perfectly replicates an original valve made by traditional
manufacturing techniques, (b) 3D printing technology efficiently creates ample options by manufacturing T-connector,
Y-connector, etc. for using a single ventilator for multiple patients
Fig.6 :(a) a close-up of three NP sticks that depict the intricate geometries of the instrument, (b) a batch of the NP swabs
printed by Carbon3D’s DLS technology, (c) Formlab’s manufactured a variety of NP swabs with the SLA technique of vat
polymerization

12. AM IN CONSTRUCTION INDUSTRY
 In the construction sector, architectural models have been created with AM methods for more
than a decade.
 Recent years have seen a vast increase in research on printing methods for building
components.
 AM allows building companies to produce geometrically complex structures, to vary
materials within a component according to its functions, and to automate the construction
process starting from a digital model.
 The technology can bring significant benefits to the construction industry in terms of
increased customization, reduced construction time, reduced manpower, and construction
cost. 12

13. 13
 Challenges to construction include
1. Work in harsh environments
2. Decrease of skilled workforce
3. Safety during construction
4. Production of large amounts of waste material
5. Transportation of materials to the site
 These challenges and limitations to innovation can be seen as opportunities for AM.
 Although all the 7 AM processes have been explored in many different industries, AM
technologies in the construction sector are in the earlier stages of development with initial
applications primarily focused on material extrusion processes for large-scale components.
 Also Binder Jetting, Powder Bed Fusion and Direct Energy Deposition methods are focused
on small scale applications.

14. 14
Table 1 : Example of AM technologies in the construction industry

15. 15
 ISO/ASTM 52900 categorizes materials for AM as metallic, polymer, ceramic, and composite,
where composite materials are defined as any combination of the other material categories.
 From the table we can say that most of the work being done so far has been in cementitious
material extrusion.
 Material extrusion process is the most commonly recognized AM process with many affordable
and often open-source, extrusion based printers accessible in the mainstream.
 Cementitious-based materials are the most studied option for widespread use in additive
construction.
 Vat photo polymerization, material jetting, and sheet lamination has yet to be explored in the
construction industry.
 For large-scale applications, vat photo polymerization would require large quantities of liquid
light-activated polymer and a larger system, making this process complex and expensive to
reproduce at larger scales.
 Small-scale applications using vat photo polymerization and material jetting processes for
construction could be explored, but degradation of the polymer's properties over time often push
this technology towards molding rather than final part production.

16. 16
 Most of the technologies deliver material using a gantry system.
 Gantry systems are based on a Cartesian coordinate system, where the nozzle or building
platform moves in three axes (X, Y, Z).
 Although gantry systems have been most commonly used, they do have limitations such as
transportation, installation, orthogonal deposition, and size of the system.
 When producing a large-scale component, a gantry system must be larger than the component
being built, complicating not only the design of the gantry system, but also the transportation
and labor-intensive installation of such a system.
 Some AM technologies have explored the use of a robotic arm or other systems such as small
robots and delta systems that are similar to gantry systems without a fixed frame.
 Robotic arms increase freedom due to a six-axis motion and flexibility to program multiple
tasks. A robotic arm requires less space than a gantry system and can even be mounted to a
transportable platform to provide on-site mobility.

17. CONTOUR CRAFTING
 One of the main AM technologies developed for the construction industry is Contour
Crafting, which is a layered fabrication technology that uses robotic arms and extrusion
nozzles.
 This process uses a concrete-like material to form a building's walls via a programmed crane
or scaffold.
 These machines have a XYZ gantry system, a nozzle assembly with three motion control
components (extrusion, rotation and trowel deflection) and a six-axis coordinated motion
control system.
 The key feature of Contour Crafting is the use of two trowels, which basically act as two solid
planar surfaces, to create smooth and accurate surfaces on the object being manufactured.
17

18. 18
Fig.7 : Contour Crafting nozzle head printing cementitious materials
Fig.8 : Contour Crafting of curved wall

19. 19
Fig.9 : Office building in Dubai printed by WinSun
 WinSun is a Chinese company that worked jointly with architectural and structural design
companies such as Gensler, Thornton Tomasetti, and others to build an office building for the Dubai
Future Foundation which was printed in Shanghai, shipped to Dubai, and then assembled on site.
 The office building was printed in segments in 17 days and required only two days to assemble on-
site
 Compared to conventional construction techniques the labor was reduced by 50 to 80% and
construction waste was reduced by 30 to 60%.

20. 20
Fig.10 : The hotel suite interior printed in Philippines
 In September 2015, the interior of a hotel suite in Philippines sizing 12.5×10.5×4 m, was
printed by Andrey Rudenko, becoming the first operational and commercial oriented
structure created using AM.
 The completion of the project took 100 h of print time, although the process was not
continuous.

21.  Construction components of medium to large size are heavy and could weight up to five tonnes.
Lifting and moving these parts is not easy and economical.
 Knowing this, Apis Cor company printed a house in Russia using mobile 3D printing technology.
 The automated printing of self-bearing walls, partitions and building envelope was done in 24 h,
totalling a 38𝑚2
printed building area.
 Apis Cor claims that this printer is easy to transport to any site and does not need long preparation
before the start of construction work, taking advantage of its built-in automatic horizon alignment
and stabilisation system.
21

22. 22
Fig.11 : (a) Apis Cor™ mobile 3D printer and its specification and (b) the robotic 3D printer in action

23. 23

24. 24

25. 25
Fig.12 : The relationship of systematic parameters for large-scale AM implementation in construction

26. 26
 For a successful implementation of AM in large scale construction, three main parameters which
are interrelated in sequence, need to be carefully addressed:
1. Printable feedstocks: the source and composition, mix design with different additives and
particle size all play an influential role in the core of feedstock developments. With the aim of
optimised blending of feedstocks to have the appropriate open time and setting time to enable
the continuous extrusion and delivery to the nozzle.
2. Printer: printer integrated with a pump is essential for the scale of manufacturing in
construction industry. Therefore the pressure and flow rate have to be investigate in
accordance with different mix designs. The speed and the size of the printer set up is also
dominant in achieving a good print quality, i.e. smooth surface, square edges and dimensional
consistency.
3. Geometry: the tailored design and outcomes of previous two parameters will directly feed
into the realisation of full size building blocks/objects with smart self-reinforced geometry.
The shape stability of deposited filaments and 3D curvatures, truss-like structures could then
provide the strength and stiffness of the printed objects/ building blocks.

27. MATERIALS FEEDSTOCKS FOR AM IN CONSTRUCTION
 Material science inevitably counts as a vital work force that dictates the success of AM
technology in the sector.
 The printable feedstocks formulations are typically a combination of bulk materials (e.g. soil,
sand, crushed stone, clay, recycled aggregates) mixed with a binder (e.g. Portland cement, fly ash,
polymers) and workability additives/ chemical agents.
 Mainly used material are
1. Cementitious materials
2. Polymer materials
3. Metallic materials
27

28. CEMENTITIOUS MATERIALS
 Cementitious-based materials are the most studied option for widespread use in additive
construction.
 This is because of their unique fresh and hardened characteristics and the extensive variety of
possible feedstocks to be generated (including rheology modifying agents) and admixtures
available to tailor their performance.
 There are no relevant guidelines or set of procedures for assessing mixtures suitable for printing
with cementitious-based materials. This make it harder for non-experts to optimise mix designs.
 Extruded cementitious-based materials require fast-setting and low slump as the material is
unsupported after leaving the extrusion nozzle.
28

29. 29
 The controlling parameters are highly dependent on parameters such as the density, particle size
and especially viscosity, which is a function of the mix composition and water to cement ratio.
 Admixtures are applied to achieve specific properties such as self-compaction (i.e. super
plasticizers), high cohesion/strength (i.e. silica fume), low CO2– foot print and increased
workability (i.e. fly ash), ductility (i.e. micro-fibres), viscosity modifying agents and so on.
 Even a slight variation in the mix design has a definite impact on the fresh state material
behaviour, which is crucial for the extrusion procedure and for the subsequent hardening and
curing stages.
 The rheological properties of cementitious based materials are crucial to its flow characteristics,
i.e. pumping pressure required.

30. PROPERTIES OF PRINTABLE CEMENTITIOUS MATERIALS
 A comparative analysis of materials feedstocks used by researchers and companies is commonly
difficult due to trade secret that prevent crucial technical details from being publicly shared.
 Concrete Printing research group of Loughborough University ,that provided some information on
the material mix used, which mainly consisted of 54% sand, 36% reactive cementitious
compounds, and 10% water by mass.
 The binder material used was a mix of CEM I cement, fly-ash, and un-densified silica fume. A
retarder, superplasticizer and an accelerator were also used. Their mix contained polypropylene
micro fibres to reduce shrinkage and deformation.
 The resulted cementitious-based print had a density of 2350 kg/𝑚3
, a compressive strength of 75–
102 MPa, a flexural strength of 6–17 MPa and a tensile bond strength between layers of 0.7–2
Mpa. 30

31. 31
 In another study from the same group, a mix of 70% cement, 20% fly ash and 10% silica fume,
together with 1.2 kg/𝑚3
micro-polypropylene fibres resulted in a maximum compressive strength
of 110 MPa after 28 days, and an optimum open time of up to 100 min.
 Hambach and Volkmer used 61.5% by weight of type I 52.5 R Portland cement with 21% by
weight of silica fume, 15% by weight of water and 2.5% by weight of a water reducing agent,
they also added 1 vol% of short (3-6 mm) carbon fibres, this yielded a flexural strength of 30
MPa, and compressive strength of 83 MPa, with an overall mix design density of around 2000
kg/𝑚3
.
 Khalil ,reported an optimised mix ratio of 93% Ordinary Portland Cement (OPC) and 7% Calcium
Sulfo-aluminate cement with water to cement ratio of 0.35, sand to cement ratio of 2, and 0.26%
of superplasticizer of the total weight of the binder which was suitable for 3D printing.
 The compressive strength of the aforementioned mix ratio was 79 MPa for printed specimen
compared to 88 MPa for casted specimen.

32. POLYMER MATERIALS
 AM of polymers has been widely explored for many possible and diverse applications such as in
aerospace industries for creating complex lightweight structures, in architectural industries for
structural models, in art fields for artefact replication or in education, and medical fields for
printing tissues and organs.
 Most of these products are still used as conceptual prototypes instead of functional mechanisms,
since pure polymer products built by AM lack strength as fully functional and load-bearing
components.
 Polymer materials such as photosensitive resin, nylon, elastomer, acrylonitrile- butadiene-styrene
(ABS) and wax can be used to produce parts with the Stereo lithography (SLA), Selective Laser
Sintering (SLS), Fused Deposition Modelling (FDM) and Three Dimensional Printing (3DP)
processes.
32

33. PROPERTIES OF PRINTABLE POLYMER MATERIALS
 Most of the printed composites still have low mechanical performance and are not able to meet
the functional requirements and standards of construction.
 The main reason for their lower mechanical strength is the presence of voids in the printed parts.
 The addition of reinforcement may further increase the porosity due to the poor interfacial
bonding with matrix.
 To homogeneously disperse reinforcements and remove the voids formed, suitable compatibilizers
should be used to enhance the compatibility i.e. interfacial bonding between the polymer matrix
and fibres/fillers.
33

34. 34
Table 2 : The techniques and materials used for AM of polymer composites
 While an increasingly higher fibre content results in composites with better mechanical
properties, typically the maximum adding content of fibres is restricted to around 40 wt%, as
the composites with more fibres are difficult to print due to nozzle clogging issues.
 Also, making them into continuous filaments for FDM is hindered by their loss of toughness

35. METALLIC MATERIALS
 In order to print metal parts, powder bed fusion and directed energy deposition processes can be
applied.
 Commonly used metals for AM are steels, titanium and its alloys, as well as aluminum alloys.
 AM has been used to construct small-scale metallic parts in many industries, including antenna
brackets for the aerospace industry, complex sand molds to cast a turbine wheel in a single piece
for the energy industry.
 when moving to larger scales, factors such as printing time and cost may limit the advantages of
large-scale AM applications of metals.
 Table 1 shows that metallic material is the group that is least explored, with two of the examples
(those using Powder Bed Fusion) being small-scale applications.
35

36. OPPORTUNITIES AND CHALLENGES
 Conventional construction processes such as bricklaying, installation of reinforcement, and
concrete casting involve heavy manual labor and are often dangerous.
 AM could also be used for construction projects in harsh environments, for example in places
affected by natural disasters, war zones, or extraterrestrial locations.
 Apart from the aspect of automation, AM offers great freedom of design. By combining and
varying the raw materials during the AM process, it is possible to produce objects consisting of
functionally graded materials.
 Complex external and internal geometries can be obtained to improve the functionality or
appearance of a building part.
 Another geometry-related constraint resulting from the layer wise approach is the surface
roughness. A smaller layer thickness or finishing operations can lead to a higher surface accuracy
and smoothness, but also to a longer production time.
36

37. CONCLUSIONS
 AM is having an impact on many industries and growing as an alternative or complimentary
approach relative to other manufacturing methods such as formative and subtractive processes.
 Aerospace, automotive, and other industries have explored the benefits of using AM in their day-
to-day activities, finding new applications for different AM processes.
 The construction industry has become interested and has started exploring AM applications
looking to mitigate current challenges such as worker safety in harsh environments, decreases in
skilled workforce availability, and waste of materials.
 While there are a range of AM technologies, most work in the construction industry has been
focused on material extrusion process using cementitious materials for large-scale applications.
 Work with cementitious material extrusion is perhaps due to the experience of the sector with the
material and the availability of material extrusion systems to experiment with.
37

38. 38
 AM applications of metallic materials for large-scale components are the least explored area due
to high costs.
 Interdisciplinary research is still needed to make AM a reliable and economically viable option in
construction.
 This field is still in its infancy, without standardized testing and quality control to compare or
benchmark these recent advancements.
 Many of these early projects and AM technologies are proprietary, lacking publically available,
detailed information on the methodology and final part quality, making comparison or evaluation
of new AM technologies more challenging.

39. REFERENCES
1. A. Paolinia, S. Kollmannsbergera, E. Rank, Additive manufacturing in construction: A review on
processes, applications, and digital planning methods, Addit. Manuf. 30 (2019) 100894,
https://doi.org/10.1016/j.addma.2019.100894
2. D. Delgado Camacho, P. Clayton, W.J. O’Brien, C. Seepersad, M. Juenger, R. Ferron, S.
Salamone, Applications of additive manufacturing in the construction industry – a forward-
looking review, Autom. Constr. 89 (2018) 110–119, https://doi.org/10.1016/j.autcon.2017.12.031
3. S.H. Ghaffar, J. Corker, M. Fan, Additive manufacturing technology and its implementation in
construction as an eco-innovative solution, Autom. Constr. 93 (2018) 1–11,
https://doi.org/10.1016/j.autcon.2018.05.005
4. P. Wu, J. Wang, X. Wang, A critical review of the use of 3-D printing in the construction
industry, Autom. Constr. 68 (2016) 21–31, https://doi.org/10.1016/j.autcon.2016.04.005
39