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Abstract

Recent years have seen a rapid growth of additive manufacturing methods for concrete construction. A recurring issue associated with these methods, however, is the lack of ductility in the resulting product. In cases this is solved by combining printing with conventional casting and reinforcing techniques. Alternatively, this paper presents first findings on the development of a system to directly entrain a suitable form of reinforcement during printing. A device is introduced to apply the reinforcement. Several options for online reinforcement medium are compared for printability and structural performance, based printing test runs and 4-point bending tests respectively. It is shown that high-performance steel cables can provide suitable reinforcement characteristics, although improved bond would allow better use of the cable capabilities. Significant post-cracking deformations and post-cracking strength can be achieved. Further research into optimal reinforcement placement and configuration is recommended.

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... Executive accessories can enhance the printing quality by embedding reinforcements, as shown in Figure 10b, such as fish lines [99] and steel wires [99], smoothing the outer surface by a controllable side trowel [100,101], accelerating the hydration by microwave [102], or brushing cement paste as glue [94] between filaments/layers. Meanwhile, from traditional cement extruding studies, the cement paste extruding operation can be enhanced by vibration operations [103] and electrode lubricating [104]. ...
... Executive accessories can enhance the printing quality by embedding reinforcements, as shown in Figure 10b, such as fish lines [99] and steel wires [99], smoothing the outer surface by a controllable side trowel [100,101], accelerating the hydration by microwave [102], or brushing cement paste as glue [94] between filaments/layers. Meanwhile, from traditional cement extruding studies, the cement paste extruding operation can be enhanced by vibration operations [103] and electrode lubricating [104]. ...
... Long reinforcements, such as wires, cables, or chains, can be embedded in the strip when the cement is extruded. Steel chain [122], steel cable [16], fish lines [99], and wires [99] can be embedded into the extruded filaments along with the printing process. Tensile strength was significantly improved by 82.5% with embedding steel cables [16]. ...
Article
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The three-dimensional (3D) printing technique for cement-based materials has been actively investigated and utilized in civil engineering. However, there is no systematic review of the fabricating devices. This paper reviews the software and hardware for extrusion-based 3D concrete printing. Firstly, a dedicated tool path generating software is urgently needed to meet the cementitious printing applications and to improve printing quality with toolpath optimizations. Secondly, the existing printing equipment was summarized and discussed, concluding the pros and cons of various 3D motion systems, material systems, and nozzle units. Suitable choices for scientific research and engineering applications were recommended. The reinforcing techniques were categorized and concluded with the existing drawbacks and the research trend. A hybrid manufacturing system of 3D printing and the reinforcing technique was then proposed with a system diagram and flowchart.
... As determined by Anjum et al. [136] through a survey to stakeholders of the Indian construction sector, numerous advantages are expected to stem from the application of 3DPC instead of traditional construction techniques. While some authors [17,137] prefer to focus on detecting unsolved challenges and proposing solutions, the vast majority of studies on this topic mention some of the advantages of this new technology [65,77,138]; however, only a few actually analyze them. In this section, a review of the advances made in their exploration and quantification is presented in order to identify those that have been more frequently approached and those avenues maybe needing further attention in forthcoming research. ...
... Jagoda et al. [138] provided an overview of several advantages: the unnecessary formwork, efficiency of the process, reduced labor demand, and cost reduction. Concretely, the latter resulted in 50% higher costs than conventional construction techniques due to the special printing material being far more expensive than conventional concrete. ...
... The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Automation/Pro ductivity 32 37% [22,29,[36][37][38]40,70,80,84,98,130,136,138,150,[153][154][155]157,164,167,168,[172][173][174]177,179,180,[183][184][185] 5 6% [55,141,142,151,152] ...
Article
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In the last few years, scattered experiences of the application of additive manufacturing in the construction of buildings using 3D printing with robots or automated equipment have emerged around the world. These use a variety of procedures and suggest relevant advantages for the construction industry. In order to identify the different processes and features in development in this field and to guide future research and applications, this article presents a review of the literature on the main aspects involved in the use of 3D printing in the construction sector. The review includes state-of-the-art material mixtures, printing technologies, and potential uses, as well as a novel analysis of building strategies, management systems, and benefits stated about this new approach for construction. It reveals progressive experimentation regarding diverse features, with challenges related to the consolidation of procedures and this technology’s readiness to participate in the building market.
... The compressive strengths of 3D-printed fiber-reinforced concrete can be up to 107 MPa [23]. Long reinforcements, such as st chains [24], steel cables [13], fish lines [25], and wires [25][26][27][28], can be embedded into truded filaments during the printing process. The reinforcements can also be placed acr the interfaces to lock the adjacent layers by inserting steel rebar [29,30], nails [31], me printed rebar [16], or plastic-printed rebar [16]. ...
... The compressive strengths of 3D-printed fiber-reinforced concrete can be up to 107 MPa [23]. Long reinforcements, such as st chains [24], steel cables [13], fish lines [25], and wires [25][26][27][28], can be embedded into truded filaments during the printing process. The reinforcements can also be placed acr the interfaces to lock the adjacent layers by inserting steel rebar [29,30], nails [31], me printed rebar [16], or plastic-printed rebar [16]. ...
Article
Full-text available
Lack of reinforcements is an existing drawback of 3D printed cementitious components, which is an urgent concern. A staple-inserting apparatus was developed and installed on a 3D printer and automatically fabricated 3D printed and staple-reinforced components with 98% successful insertion to achieve inner- and inter-reinforcement of the printed strips. The inserted staples inside the printed strips improved the compressive strength by 25% maximum owing to the inner locking effect by the staple pins, while the flexural strength did not increase because the scattered staples functioned separately. The staples over the strip interfaces remarkably increased the flexural stress by 46–120%. The inserted staples demonstrated a significant strip locking effect, but the unavoidable voids decreased the bonding between staples and the composite. The mechanical analysis concluded that the printing parameters considerably affected the reinforcing rate. The staple inserting technique proved the feasibility of automatic fabrication of fiber-reinforced and printed concrete structures.
... The majority of articles related to the assembly of steel structures (6 articles) and prefabricated buildings and elements (1 article) discussed the use of the automated robotic assembly. (14 ), interior finishes(1) (Hwang and Khoshnevis, 2005, Bosscher et al., 2007, Lim et al., 2011, Zhang and Khoshnevis, 2013, Cesaretti et al., 2014, Gosselin et al., 2016, Hung et al., 2016, Bos et al., 2017, Panda et al., 2017, Subrin et al., 2018, Zhang et al., 2018, Ye et al., 2018, Panda et al., 2018, Izard et al., 2018 al., 2019) Automated installation system A manipulator or CDPR robotic system with suction/grasping devices in a mobile platform or connected to a frame/gantry that allows automatically installing of building elements 9 ...
... In-situ robotic fabrication system (Bos et al., 2017) 3D printing concrete with reinforcement Additive manufacturing (AM) (Panda et al., 2017) Automation of robotic concrete printing using feedback control system Additive manufacturing (AM) (Felbrich et al., 2018) A novel rapid additive manufacturing concept for architectural composite shell construction inspired by the shell formation in land snails Fused filament fabrication (FFF) (Subrin et al., 2018) Improvement of the mobile robot location dedicated for habitable house construction by 3D printing (Kaneko et al., 2019) Humanoid robot HRP-5P: An electrically actuated humanoid robot with high-power and wide-range joints Autonomous robotic assembly J o u r n a l P r e -p r o o f ...
Article
Robotic technologies for building construction represent a significant departure from conventional construction approaches. The use of robots is likely to bring a host of opportunities that transform the way we design and construct buildings. To gain an improved understanding of the trend and trajectory of research on robotics application for on-site building construction, this paper provides a systematic review of 52 articles identified through the PRISMA protocol and meta-analysis. The results show that robotic technologies for on-site construction is a growing application field, where additive manufacturing (AM), automated installation system, automated robotic assembly system, autonomous robotic assembly, and robotic bricklaying seem to be most studied and have a potential to influence the development of robotics research in building construction. While most research discussed single construction activities related to vertical reinforced concrete (RC) elements, masonry walls, steel beams, curtain walls, gypsum boards, and floor tiles, only a few papers proposed an integrated robotized construction site. It is suggested that the building construction industry and research organizations could benefit from the current product and work processes that can be improved by taking some measures through innovative construction materials, improved robotics hardware, and more advanced engineering design to streamline construction workflows to achieve a complete on-site robotic system.
... In 2017 a method was presented at TU Eindhoven for reinforcement of an extrusion-based 3D-printed concrete, longitudinal filament by directly entraining a high strength steel cable into the filament [36]. Actively fed from a spool by a small servo motor with an appropriately flexible cable, this allows a fully automated process that does not reduce the geometrical possibilities of the 3DCP technology. ...
... Cable entrainment in the filament [36,38,39,45,75,76] Continuous fibre entrainment [39,44,77] In-process reinforcement method. Only in u-direction. ...
Article
This article offers a comprehensive, systematic overview of the existing solutions for integrating reinforcement in digital concrete technologies with particular emphasis on Additive Manufacturing (AM) with concrete, also called 3D concrete printing (3DCP). While the functionalities of various types of reinforcement are briefly addressed, the major focus is on the integration process as such, i.e., on its technological aspects. On this basis a generic classification and process description outline has been developed for reinforcement integration, which is regarded as an extension of the RILEM process classification framework for Digital Fabrication with Concrete (DFC). In many instances, the integration occurs in a separate process step prior to or after concrete shaping. This holds true for all formative digital concrete shaping processes and for many 3DCP solutions. 3DCP approaches enable, however, integration of the reinforcement during concrete shaping as part of a single-step AM process in a simultaneous or contiguous manner, while placement of reinforcement is considered to be a sub-process.
... (g) Online reinforcement integration in the concrete filament: In this process, formable (flexible) reinforcement elements (textile reinforcement, cables, etc.) are fed to the extruded concrete filament in the print head so that the resulting component is reinforced parallel to the extrusion direction [25]; ...
... First, concepts for combined print heads for reinforcement and concrete rely on techniques for simultaneous insertion/unrolling of textile or metallic, thread-like reinforcement elements from coils in the print head [25]. The so-called online reinforcement integration in the concrete filament (g) allows for an excellent durability of the reinforcement, because the flexible reinforcement elements are already fed to the extruded concrete filament in the print head. ...
Article
Full-text available
Reinforced concrete (RC) is by far the most widely used composite material in the world. Despite the enormous economic importance of RC construction, there is a lack of viable concepts for its digital fabrication. While 3D printing of plain concrete has been pushed forward by a growing research community in recent years, methods for integration of steel reinforcement have only scarcely been researched and little attention has been payed to meet the practical requirements of construction sites and prefabrication plants. Therefore, full-scale implementations of current approaches are hardly available. Based on both, a sound review of R&D for digital fabrication of RC structures and an analysis of practical requirements, the present paper proposes a novel 3D printing process for RC structures, called Additive Manufacturing of Reinforced Concrete (AMoRC), viable for real-world application. In this hybrid process, consisting of an intermittent stud welding process and a continuous concrete extrusion process, segmented steel reinforcing bars are joined to form a three-dimensional reinforcement mesh and simultaneously encased with extruded concrete. The paper describes the conceptual design and development of the process and demonstrates the results of preliminary investigations on its feasibility. As AMoRC enables the operation of rebar welding and concrete extrusion process with synchronized feed rates, combination of both processes in one hybrid print head for digital fabrication of RC is a key-advantage of the proposed method.
... However, for 3D printed concrete the incorporation of traditional steel rebar reinforcement is not straightforward [5,6], as a result of which several alternative solutions have been considered. Firstly, the application of passive reinforcement steel has been suggested, for example, by using reinforcement meshes [7], by connecting the printed concrete element to an external steel reinforcement framework [8], or through the application of an advanced printing nozzle that lays down a steel wire within the concrete layer during its printing [9,10]. Secondly, post-tensioned, pre-stressed reinforcement may be applied. ...
Chapter
Full-text available
Over the past few years, several studies have shown the potential of three-dimensional concrete printing (3DCP) for applications in building and civil engineering. However, only a few studies have compared the properties of the fresh printing material and the quality of the printed elements from different printing facilities. Variations in the manufacturing conditions caused by the mixing procedures, the pumping device and the nozzle shape and/or dimensions may influence the quality of the printed elements. This study investigates the differences in the fresh and hardened properties of a printing material tested in two different printing facilities. The pump pressure and temperature experienced by the printing material during the printing session are monitored real-time. Hardened properties are measured for the printed elements, such as the bending capacity, the apparent density, and the air void content. The research shows that two different printing facilities may result in printed elements with relative differences in flexural strength and volumetric density of 49% and 7%, respectively.
... These weak interfaces, together with typical thin-walled filament 3DCP construction, may possibly be negatively affected by self-equilibrating mechanical stresses resulting from thermal strains [5]. Thirdly, a process is yet to be developed that automatically includes steel reinforcement in the 3DCP construction process, although many attempts have been made to this end [6,7]. Consequently, 3D printed concrete elements lack ductility and confinement and may experience brittle failure in the event of crack initiation from the effect of high temperatures. ...
Conference Paper
This research investigates 3D printed concrete behaviour at elevated temperatures. Preliminary studies indicate that delamination of filament layers occurs at elevated temperatures, as opposed to thermo-hygral spalling, which typically occurs in conventionally cast high-performance concrete samples. Brittle structural failure may therefore occur during a fire scenario since little to no reinforcement is currently included in the 3DCP process. This research proposes the incorporation of steel fibres into the additive manufacturing process to facilitate ductile failure and increase interlayer mechanical properties. The fibres are vertically aligned, orthogonal to the printing plane, and strategically positioned to bridge multiple filament layers. 3D printed rectangular samples are heated via radiant gas panels and thereafter tested in four-point bending once they have cooled down to ambient temperature to determine post-fire flexural capacity and ductility properties. This study shows that steel fibre inclusion improves the structural fire performance of 3D printed elements by 33% and provides post-peak mechanical ductility to yield deflection softening. More research is required to ultimately develop a standardized economical structural fire design process for 3DCP.
... In 2017, researchers from the TU Eindhoven introduced a method to entrain a high strength steel wire rope cable into the extrusion filament during concrete printing. A proof-of-concept on beams in bending showed the section resistance could be analyzed analytically similarly to conventional reinforced concrete beams [16]. A subsequent study explored bond properties [17]. ...
Chapter
The use of high strength steel cables directly entrained into printed concrete during the printing process, has previously been introduced as a method to provide reinforcement to objects being manufactured through a layer-extrusion based 3D concrete printing process. The bond between the cable and the cementitious mortar is a crucial parameter for the structural performance of such reinforcement, and was hence subject of a detailed study presented in this paper. The bond performance was studied in direct and flexural pull-out tests on cast and printed specimens and further analyzed by microscopic analysis of the bond surface. Two effects were identified that significantly decrease the bond strength. Firstly, chemical reactions create a spongy interface of poor strength. Secondly, the flow of mortar around the cable tends to create a cavity underneath the cable which reduces the effective bond surface. Mortar viscosity, nozzle design and filament pressure, were thus identified as important parameters for the bond quality. The average bond quality seems to reduce with embedment length. As a consequence, cable breakage was not achieved, in spite of considerable embedment lengths that were tested. Likely, this was caused by the cumulative probability of critical defects along the increasing embedment length, in combination with a non-constant shear distribution. All test series showed significant scatter. It was concluded that, although this reinforcement method is promising as it can potentially provide sufficient post-cracking strength, the bond quality must be improved considerably both in terms of average strength and reduction of scatter.
... As mentioned before, the implementation of reinforcement in printed elements will be extremely important. Previous research [2,3] showed that, in case of reinforced concrete, the ingress of chlorides and the subsequent initiation and propagation of reinforcement corrosion is one of the major causes for durability problems. For that reason, a first evaluation of the durability is made based on the chloride ingress capacity of printed elements. ...
Chapter
Full-text available
3D concrete printing is one type of additive manufacturing (AM) which comprises all modern techniques of fabricating building elements layer by layer. It shows great perspectives with respect to freedom of form, time management and eco-friendly use of the material as the material is only applied where it is necessary. However, due to the lack of formwork and the layered end result, this construction technique induces more shrinkage, internal voids and crack formation, increasing the amount of preferential ingress paths for chemical substances. The additional amount of voids caused by this layered fabrication technique will not only induce anisotropic properties on a structural level, but will also affect the microstructure and durability of the printed specimens. For the aim of this research, 3 different time gaps are selected to investigate the influence of the layered construction process on chloride penetration and a comparison with traditional cast concrete was made. First results showed that the print process affects the chloride penetration in a significant way. Although the ingress front is uniform in both cases, the chloride ingress is approximately three times higher in case of specimens fabricated with a zero minute time gap compared with traditional cast elements and this only after one week of chloride exposure. An increased time gap increases the porosity at the interface and consequently also the chloride ingress rate of the printed elements.
... AM, also known as 3D printing technology, is an important disruptive technology that was recently introduced to civil infrastructure. Layering material on different slices makes it possible to engineer its properties in terms of composition, quantity, or printed infill pattern parametrically to meet structural requirements in a customizable and optimal way (Bos et al. 2018;Buswell et al. 2018). There are many AM techniques; the most widely used for infrastructure applications is the contour crafting technique, as suggested by Khoshnevis and Dutton (1998). ...
... In this case, steel bars are entered horizontally and drawn automatically through special openings. Bos et al. (2018) developed a device to directly entrain a reinforcement medium into the filament of the printed concrete. In this method, wire reinforcements with high flexibility are used, allowing the print head movement in 3D space. ...
Article
Industrialized construction leverages factory-based manufacturing and lean-site assembly to achieve higher industrial efficiency. Building information modeling (BIM) offers new opportunities to underpin the computerized design and fabrication of industrialized buildings, providing greater productivity and cost-effectiveness. In this study, attempts are made to review the state-of-the-art BIM applications on design and prefabrication automation of industrialized buildings, with more emphasis on the recent achievement in concrete 3D printing technology. Following this, a BIM method is proposed to support the detailed geometry design and digital fabrication of modular housings. A program interfaced within BIM is developed and demonstrated through discussions on its capacity in generating the geometry details of 3D-printed modules. In addition, robotic simulation of 3D printing is performed to explore a flexible plan in producing the 3D-printed modules or components. The lessons learned from the study are discussed to highlight the future research challenges and opportunities. First, as current Industry Foundation Classes-based BIM model provides limited support to prefabrication, research on BIM open standards demands more attentions to interoperate the computerized design and computer-aided manufacturing. Moreover, today’s industrialized buildings consist of sophisticated architectural, structural, and mechanical systems that are intervened across the whole life cycle, more research on the interdependent building systems is needed (via digital twins) to optimize the life cycle performance. When moving towards data-driven decision making, there are research needs to expand Internet of Things and Artificial Intelligence to collect the big data from prefabrication, perform predictive analysis, and optimize the control decisions for manufacturing facilities operation. This study illustrates the process and future work in BIM design and prefabrication automation that can assist practitioners to enhance the quality of industrialized construction.
... It should also be fast setting, so as not to lose shape without formwork [19][20]. If it is necessary for concrete to have greater strength, steel [21][22][23][24][25][26]. Possible flexural strength is up to 30 MPa and compressive strength is up to 80 MPa in the case of using carbon, glass and basalt fibers with a size of 3-6 mm [27][28]. ...
Article
Full-text available
The subject of research is expanded-clay concrete with additives of ground granulated blast-furnace slag, silica fume, superplasticizer and air-entraining admixture. The heat release of concrete is investigated depending on the concrete composition (cement, water cement ratio, expanded-clay), additives (slag, silica fume) and admixtures (superplasticizer, air-entraining agent). This study is a part of research on the design concrete mixture with strength class C35/45 and high workability for 3D printer. It was confirmed that the cement content and water cement ratio impact on the integral value of the heat release per unit mass of cement. This value decreases with increasing cement content. The reason for this is that the heat generated by concrete, with constant W/C and other equal conditions, increases linearly with increasing the cement content.
... Controlling the height between layers is an important parameter during printing to avoid deviation in either direction that influences the quality, geometry, and appearance of the final printed product. In this work, we considered a height between layers of 0.01 m, which is the minimum distance of printing in the construction process [57] and a vertical displacement of 0.50 m for our experiments. A crucial factor in 3D printing is the velocity of operation of the robotic system. ...
Article
Full-text available
The construction industry is currently technologically challenged to incorporate new developments for enhancing the process, such as the use of 3D printing for complex building structures, which is the aim of this brief. To do so, we show a systematic study regarding the usability and performance of mobile manipulators as displaceable 3D printing machinery in construction sites, with emphasis on the three main different existing mobile platforms: the car-like, the unicycle and the omnidirectional (mecanum wheeled), with an UR5 manipulator on them. To evaluate its performance, we propose the printing of the following building elements: helical, square, circular and mesh, with different sizes. As metrics, we consider the total control effort observed in the robots and the total tracking error associated with the energy consumed in the activity to get a more sustainable process. In addition, to further test our work, we constrained the robot workspace thus resembling real life construction sites. In general, the statistical results show that the omnidirectional platform presents the best results –lowest tracking error and lowest control effort– for circular, helicoidal and mesh building elements; and car-like platform shows the best results for square-like building element. Then, an innovative performance analysis is achieved for the printing of building elements, with a contribution to the reduction of energy consumption.
... As it is generally recognized, the lack of suitable reinforcement methods could seriously hinder the potential applicability of the technology [14,15], several options are being developed by different groups. Until now, only two strategies have been presented that are fully integrated with the 3DCP process: the automated entrainment of reinforcement cable [16][17][18][19], and the application of fibres which will be further discussed in this manuscript. ...
Article
Full-text available
Extrusion based additive manufacturing of cementitious materials has demonstrated strong potential to become widely used in the construction industry. However, the use of this technique in practice is conditioned by a feasible solution to implement reinforcement in such automated process. One of the most successful ductile materials in civil engineering, strain hardening cementitious composites (SHCC) have a high potential to be employed for three-dimensional printing. The match between the tailored brittle matrix and ductility of the fibres enables these composites to develop multiple cracks when loaded under tension. Using previously developed mixtures, this study investigates the physical and mechanical performance of printed SHCC. The anisotropic behavior of the materials is explored by means of mechanical tests in several directions and micro computed tomography tests. The results demonstrated a composite showing strain hardening behavior in two directions explained by the fibre orientation found in the printed elements. Moreover, the printing technique used also has guaranteed an enhanced bond in between the printed layers.
... In the direction of the main span, the pre-stressing action was applied by post-tensioned rods, anchored in cast concrete head blocks and fed through openings in the segment structure, which serve as active reinforcement (as clearly visible in the mock-up structure of Fig. 16, which is discussed in Section 4.1); this concept did not disrupt the printing process. In the perpendicular direction, an innovative concept of the entrained high-strength steel cable reinforcement was applied over a part of the height [101,102] as an experimental addition. These cables were intended as compatibility torsion reinforcement in case of misalignment in the abutments (hence, they provide an additional precaution, but the structural safety of the bridge does not rely on them). ...
Article
Digital fabrication technologies utilizing concrete (DFC) have recently enabled form freedom for the production of a variety of concrete-made objects having mainly architectural and aesthetic functions. Structural elements or civil/building structures made by DFC demonstrate a high engineering potential, mainly for tailoring the final shape while optimising the structural/functional performance, material use, overall costs, and architectural effectiveness. However, the design of structurally efficient DFC constructions or components is often faced with a lack of a common structural engineering approach that can adapt to specific DFC particularities. In this paper, we provide a systematic overview of a number of DFC structural projects developed thus far. A comprehensive discussion about structural engineering details is provided, addressing the related fundamental structural issues and envisioning opportunities and challenges toward achieving the full potential of DFC.
... In cable-based systems, the print head is strung between multiple fixed points; hence, it lacks the rigidity of the gantry system and the stiffness of any pumped-concrete hoses is an issue. While they have a smaller footprint and are more compact and easier to transport, cable-based systems also cannot execute multiple processes nor complex maneuvers (Bos et al. 2018). Manipulating the five cables provides the needed control of the nozzle's position, allowing the system to scale up more easily than the gantry system without adding much additional complexity or cost. ...
Chapter
In the past few years, the adaptation of additive manufacturing (AM) technologies for the building industry has reached new levels of sophistication, triggering design and development of novel 3D-printable materials and material interfaces; inspiring innovative architectural details; rethinking of material-specific printing systems; and enabling significant understanding of the interrelationship between multiple variables and aspects of design thinking and processes. For example, there are notable consequences of toolpath design in relation to material design, spatial experiences, and structural performance. AM has been recognized for its unique affordances, including flexibilities and freedom of free-form construction; speed of construction; reduced construction time and cost; reduced waste of resources, materials, labor, and energy; and increased safety due to innovations in automated construction. This technology has far-reaching implications and impact by augmenting conventional technologies and wisdom. This paper presents an overview of materials, systems, design explorations, and selected results in the context of NASA Centennial Challenge’s 3D-Printed Habitat Challenge Competition, leading to the production of the first fully 3D-printed, fully enclosed concrete habitat. The paper also reflects on the potential impacts of this technology when fully adopted by the construction industry.
... Assuring the required geometric quality of digitally fabricated structures is of high importance not only after but also during the construction process. Recent rapid growth of interest in robotically assisted construction [1] has also boosted the use of sensing technologies to acquire processrelevant information. These works showcased the potential of various sensors in digital fabrication processes and demonstrated ways in which accurately measured 3D information and object parameters extracted from such information can be used for in-line process improvement via feedback control [2,3]. ...
Conference Paper
This paper presents a feasibility study of surface geometry (SG) evaluation and material classification (MC) for robotic spraying. We propose two complementary approaches using point clouds and intensity data provided by a state-of-the-art industrial time-of-flight (ToF) depth camera. The SG evaluation is based on geometric feature computation within local neighbourhoods, which are then used within a supervised classification. The results of this approach are SG classes according to the level of geometric variability of the surface, displayed as SG maps. For MC, active reflectance estimation is investigated and exploited to derive features related to the reflectance and diffusive properties of each material for classification. The result of both approaches can be prospectively used as feedback in digital fabrication for in-line adaptation of the process to improve control of relevant geometrical and material properties.
... The first attempt in this regard was the entrainment of steel coils by Khoshnevis et al. [20]. Following this, many researchers used specially designed print heads to have steel cables incorporated within the deposited layers [148][149][150][151][152]. Mechtcherine et al. [153] envisaged an idea of printing steel reinforcement synchronously with concrete using gas arc welding. ...
Article
This paper provides a comprehensive review of the material behaviour for extrusion-based concrete 3D printing spanning from the early age to long-term performance. We begin with a discussion on the recent progress on the understanding of early-age behaviour. Following this, the mechanical response in the hardened state, and the different strategies to introduce reinforcement are reviewed. Finally, we present insights and perspectives on the transport mechanisms in printed concrete to assess the long-term performance, and also discuss the overall impact of construction by concrete 3D printing on sustainability.
... Voids and porosity are because of the poor manufacturing of the material for the feedstock filament [164]. Voids can be the reason for the cracking when a small load is applied to the filament [165] (see Fig. 10). Voids and porosity affect the properties of the material like compressive strength and tensile strength [166]. ...
Article
Full-text available
Fused filament fabrication (FFF) is one of the additive manufacturing (AM) techniques that have revolutionized the manufacturing strategy in the last 2 to 3 decades. The quality of the parts prepared by the FFF process is dependent upon the static and variable process parameters. It has been reported by previous studies that part shrinkage, part shrinkage, high surface roughness, warping from the edges, misaligned part geometry, lack and loss of the adhesion, part distortion, voids and porosity etc., are the major issues in the fused filament fabrication process. In the case of open-source fused filament fabrication, internal and external factors such as; the variable room temperatures, room humidity, wind speed, heterogeneity in feedstock materials, torsion in feedstock filaments, vibration due to any source, nozzle clogging, nozzle choking, high/low nozzle and bed temperature are conducive for the mentioned issues. The present study is the state of review for minimizing defects in the final product by suggesting the methods and procedure for each issue in the FFF process. This study would be helpful for novice researchers who are working on different applications of the FFF process. In this review work, most common defects and problems observed during 3D printing are elaborated and discussed according to literature review and also solution of defects has been discussed.
... This section explores point-supported ribbed slabs with 3D concrete printed (3DCP) elements that serve as a stay-inplace formwork. The provision of reinforcement within printing layers (see [48,49]) renders the structural activation of the printed material in the final slab possible, thus minimising the overall concrete use. After assembling the 3DCP formwork on-site, conventional reinforcing steel and concrete can be used to realise a monolithic, two-way loadbearing slab. ...
Article
Full-text available
The concrete used in floor slabs accounts for large greenhouse gas emissions in building construction. Solid slabs, often used today, consume much more concrete than ribbed slabs built by pioneer structural engineers like Hennebique, Arcangeli and Nervi. The first part of this paper analyses the evolution of slab systems over the last century and their carbon footprint, highlighting that ribbed slabs have been abandoned mainly for the sake of construction time and cost efficiency. However, highly material-efficient two-way ribbed slabs are essential to reduce the environmental impact of construction. Hence, the second part of this paper discusses how digital fabrication can help to tackle this challenge and presents four concrete floor systems built with digitally fabricated formwork. The digital fabrication technologies employed to produce these slab systems are digital cutting, binder-jetting, polymer extrusion and 3D concrete printing. The presented applications showcase a reduction in concrete use of approximately 50% compared to solid slabs. However, the digitally fabricated complex formworks produced were wasteful and/or labour-intensive. Further developments are required to make the digital processes sustainable and competitive by streamlining the production, using low carbon concrete mixes as well as reusing and recycling the formwork or structurally activating stay-in-place formwork.
... In the absence of a universal reinforcement system, compatible with the 3DCP process, reinforcement integration has to be project-specific. Structural 3DCP columns can be achieved by adding a minimum shear reinforcement in between layers or directly in the extruded filament and add the main reinforcement inside cavities that follow the column height [14,22,40,41]. The main reinforcement can be external posttension or post-tension inside grouted cavities. ...
Article
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Recent developments in computational design and digital fabrication with concrete enable the realization of freeform geometries that optimize material use. 3D Concrete extrusion Printing (3DCP) is presently one of the most utilized digital fabrication methods with concrete. The expected advantages of 3DCP result from shaping concrete without formwork and from placing material only where functionally required. Although these advantages were pointed out more than 20 years ago, it is difficult to find competitive examples and their usage in real buildings. Consequently, the nonspecific character of the process acts as a shortcoming by opening up extensive possibilities without a clear direction. This paper proposes an automated 3DCP prefabrication platform for customized columns. The process-specific parameters are, therefore, fine-tuned for high-quality products with diverse forms and textures. Additionally, this paper proposes an evaluation method for geometric complexity and identifies the types of column typologies that may benefit from a 3DCP prefabrication platform.
... AM, also known as 3D printing technology, is an important disruptive technology that was recently introduced to civil infrastructure. Layering material on different slices makes it possible to engineer its properties in terms of composition, quantity, or printed infill pattern parametrically to meet structural requirements in a customizable and optimal way (Bos et al. 2018;Buswell et al. 2018). There are many AM techniques; the most widely used for infrastructure applications is the contour crafting technique, as suggested by Khoshnevis and Dutton (1998). ...
Article
Emerging technologies (ETs) are increasingly becoming more accessible, and as they make their way into the field will be an integral part of the engineering community’s work that impacts future civil infrastructure. In the meantime, infrastructure resilience has become a recurring theme in government and industry discussions. ETs are expected to contribute to improving infrastructure resilience capacities, namely, absorptive, adaptive, and restorative. Through an extensive literature review, an in-depth conspectus of the state of the art of ETs in civil engineering is provided, leading to a vision for how these technologies impact infrastructure resilience. Three distinct disruptive technologies that can impact infrastructure resilience are demonstrated—specifically, smart materials, advanced construction technology, and advanced sensing technology. Such ETs will remarkably affect the well-known four characteristic elements of infrastructure resilience: redundancy, robustness, rapidity, and resourcefulness. These innovative technologies will warrant infrastructure to withstand or efficiently recover from multihazard disruptive events, leading to improved resilience. A roadmap to field implementation is presented considering the financial cycles necessary for ETs to make an impact on infrastructure resilience.
... Early efforts focused on the development of 3D-printing systems and mixtures designs with suitable rheological and mechanical properties [2]. More recent efforts focus on 3D-printing of structures containing reinforcement and on evaluation of their mechanical and durability characteristics [3]. In addition, the increased global interest in renewable energy generation has accelerated the development of offshore wind energy projects. ...
... • The incorporation of conventional steel reinforcement between the concrete layers is a very challenging task (Bos et al., 2018). Lacks of conventional steel reinforcement in 3D printing have limited its applications to small scale printing constructions only. ...
Article
Recently 3D printing of geopolymers gained increasing attention due to their dual-dimensional sustainability from technology and materials perspectives. The current research first defines the criteria for the assessment of the sustainability of 3D printed geopolymers. Four different aspects including productivity assessment, economic influence, environmental burden and social impact have been investigated to analyze their current states of sustainability. Detailed productivity analysis depicts promising results in terms of fresh and hardened properties of 3D printed geopolymers. Despite reasonable productivity, 3D printing of geopolymers has not completely replaced the traditional practices and materials on industrial scale as a result of their inadequate economic and environmental performance mainly due to alkaline reagents. Alkaline reagents used for the geopolymerization of industrial by-products not only increase the overall concrete cost but also induce a severe environmental burden. Although, 3D printed geopolymers have explicit social impacts on human lives, the high level of automation in 3D printing process and less manufacturing of cement (due to its replacement with geopolymers) may reduce the number of jobs. Upon critically analyzing the pros and cons, a strategic roadmap is provided for the adoption of the 3D printing of geopolymers on industrial scale based on short, medium and long-term goals.
... Recently, researchers have investigated different ways to incorporate reinforcement into the 3D printing process. One approach is to directly entrain the reinforcement (e.g., fibers, steel cables) during the extrusionbased 3D printing, which can increase the strength in the printed structures [28][29][30]. Adding reinforcement in one direction, however, can result in anisotropy in the material. Therefore, controlling fiber orientation is one of the main challenges in this process. ...
Article
Concrete exhibits inherently low ductility and tensile strength despite its high compressive strength. Typically, it must be reinforced with steel rebars, yet it still suffers from potential corrosion issues. This work proposes and examines a new method for improving the bending stiffness of cementitious beams by reinforcing with 3D printed plastic TPMS-Primitive scaffolds. Three concrete beams of the same size - including non-reinforced, reinforced with one-layer, and two-layer bioinspired thin-walled molds - are designed and fabricated for three-point bending tests and comparisons. The simulation is found to be in good agreement with the experiment in terms of stress-strain curves and crack propagation. Results show the improved load-bearing capacity of the concrete beam reinforced with 3D-printed TPMS-Primitive shells. The peak load of the two-layer TPMS-Primitive reinforced beam is 35% and 125% higher than that of the one-layer reinforced beam and the non-reinforced concrete beam, respectively. Furthermore, the TPMS-Primitive reinforced concrete beams reveal a smooth softening behavior in bending and increase ductility as well. The scalable and sustainable production of such beams for construction applications could be realized by a combination of 3D printing techniques and recycled plastic.
... One key research direction within the 3D concrete printing community is the integration of reinforcement [19][20][21]. Microfibers are added to the mixture during mixing or continuous fibers are integrated into the printed strand. In addition, the reinforcement can be inserted between or through the layers [22], or printed around a reinforcement [23,24]. ...
Article
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A promising process for the automatization of concrete structures is extrusion or extrusion molding. An innovative approach is the extrusion of concrete with imbedded technical textiles as reinforcement. For a successful extrusion, the rheological properties of the fresh concrete have to be optimized, as it must be extrudable and have sufficient early strength after leaving the mouthpiece. Within the scope of this paper, a process was developed which allows the integration of flexible as well as stiff impregnated textiles into the extrusion process. For this purpose, different textile-reinforced mortars (TRM) were extruded and their material characteristics were investigated. The results show that the mortar cross-section is considerably strengthened, especially when using carbon textiles, and that extrusion has considerable potential to produce high-performance TRM composites. In uniaxial tension tests with TRM, as well as in the pure roving tensile strength tests, textile stresses of approx. 1200 MPa were achieved for the glass textile and approx. 2250 MPa for the carbon textile. The position of the textile layer deviated a maximal 0.4 mm from its predesigned position, which shows its potential for producing tailor-made TRM elements. In addition, by adjusting the mortar mix design, it was possible to reduce the global warming potential (GWP) of the extrusion compound by up to 49.3% compared to the initial composition from preliminary studies.
... Though this technique follows a similar deposition style used in the Fused Deposition Modeling (FDM) process, the main difference lies in the solidification mechanism of concrete material, which does not set instantaneously, rather stays in an intermediate state, leading to a challenging problem for balancing extrudability and buildability criteria [8]. However, with R&D contribution by industries and academicians, many emerging problems (material design [9], processing technology [10], Reinforcement placement [11], Mechanical and durability properties [12]) have been addressed, and by the end of 2020, a total of 29 houses have been built around the globe using 3D printing technology [13,14]. Based on current state of the art, Fig. 1 marks the countries involved in 3DCP research and demonstration [5]. ...
... Therefore, manual rebar reinforcement and a few alternative techniques have been used in conjunction with C3DP (Classen et al., 2020). The alternative reinforcement techniques include inline reinforcement integration through the placement of steel wires or cables within concrete layers (Bos et al., 2018a) and pre-or post-tensioned tendons to realize pre-stressed 3D printed concrete behavior (Bos et al., 2018b;Asprone et al., 2018). All these reinforcement techniques are either manual or have not been evaluated thoroughly yet, to be considered as an acceptable reinforcement method to replace steel rebars. ...
... It is also possible to add a layer of material with good bonding strength to the mortar material between the mortar layers [65][66][67][68][69], or use some nanomaterials to improve the bonding performance between the fibers and the mortar matrix [70][71][72][73][74][75][76]. In addition, the chemical modification of polymer fibers can be used to improve the construction process and increase the performance of printing equipment, so that the fiber can penetrate the interface between mortar layers and participate in the bonding force between mortar layers [77][78][79][80]. Through the improvement of materials, machinery and process factors, the reinforcement skeleton is added in the process of mortar printing, in order to achieve fiber reinforcement, reinforcement skeleton setting, prestressed tendon tension and other multi-channel structural reinforcement system [81][82][83][84]. ...
Article
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The engineering applications and related research of fiber-reinforced cement and geopolymer mortar composites are becoming more and more extensive. These reinforced fibers include not only traditional steel fibers and carbon fibers, but also synthetic polymer fibers and natural polymer fibers. Polymer fiber has good mechanical properties, good bonding performance with cement and geopolymer mortars, and excellent performance of cracking resistance and reinforcement. In this paper, representative organic synthetic polymer fibers, such as polypropylene, polyethylene and polyvinyl alcohol, are selected to explore their effects on the flow properties, thixotropic properties and printing time interval of fresh 3D-printed cement and geopolymer mortars. At the same time, the influence of mechanical properties, such as the compressive strength, flexural strength and interlaminar bonding strength of 3D-printed cement and geopolymer mortars after hardening, is also analyzed. Finally, the effect of polymer fiber on the anisotropy of 3D-printed mortars is summarized briefly. The existing problems of 3D-printed cement and polymer mortars are summarized, and the development trend of polymer fiber reinforced 3D-printed mortars is prospected.
... On the other hand, traditional fabrication technologies are risky, slow, and energy-intensive. In combination with layer-based and freeform additive manufacturing techniques, automated construction systems could produce geometries that would be economical, if not physically, challenging to achieve with traditional construction approaches [2]. Structures built by automated building systems could be changed on the fly to site-specific environmental variables and limits [3]. ...
Chapter
3D concrete printing uses fresh concrete to create complex, nonstandard geometries and details architecture or part of architecture by layering new concrete on top of each other. As mentioned above, this method has more advantages than conventional construction, such as the absence of formwork, optimizing construct time, cost, and safety, the primary material used in 3D concrete printing. The quality of the printed constructs significantly depends on the new property of the used material. During the printing process, pre-mixed concrete is continuously hardening due to the exothermic process, which is the factor of open time. Besides, most concrete 3D printing is applicable in civil construction, requiring a solid interface concrete layer. Hence, to ensure the structure's durability, supports are needed for building and large-scale concrete printing. The preview of fresh concrete properties and their impact is summarized in the second section of this study. The most sensitive factor of a new property, an interface between layer problems, is considered in the third section. In the fourth section, we introduce the standard method to overcome these problems using supports.
Conference Paper
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Since 3D printing of structures is expected to reduce construction time, material, cost, and energy, the building industry has come to realize the relevance and importance of digital design and additive construction, signaling a foothold in that regard and paving the way for much-needed advancement in the construction industry. Furthermore, the automation implied in 3D printing technology could introduce newfound applications; for example, it makes possible in-situ construction in harsh conditions on Earth and extraterrestrial environments such as Mars and the Moon prior to the arrival of human explorers. This paper presents the dynamic and interrelated processes of design and development of materials, systems, and architectural constructs on a single BIM platform, on which the architectural design of a habitat, the tool-path design, and assembling and coordination of information regarding multiple interrelated variables such as materials properties, structural behavior, systems' transformation, costs, and logistics, can be systematically created, coordinated, managed, analyzed, and converged towards the common goal of automation in construction. Through this case study we review the attempts made by the interdisciplinary team of Penn State faculty and students to print a sub-scale habitat for Phase III-Level 3 of NASA's 3D-Printed Habitat Challenge. NASA designed the multi-phase Challenge to catalyze research to advance the automated construction technology needed to create sustainable housing solutions for Earth and deep space habitats. As such, this paper presents a framework to quantitatively understand the benefits of and changes that AM will trigger in construction and logistics, rather than a focus on qualitative consequences in terms of the inevitable transformations it will trigger in architectural language and practice. 2 2
Article
Digital construction of concrete elements using 3D printing technology has been undergoing an exponential growth in terms of research activities and demonstration projects. Though, most researches focused on the behavior of the cementitious materials used in 3D printing, without deeply immersing in the reinforcement of printed elements. In this paper, a detailed experimental program is presented to characterize the quality of the bond developed between concrete and steel bars through a series of pull-out tests. These tests are performed over printed and non-printed samples as well. When printed, the layers orientation, whether parallel or perpendicular to the steel bar is taken into consideration. Hence, it was found that a highly thixotropic material did not undermine the developed bond between printed concrete and rebar. In addition, vibrated concrete (non-printed) gave better resistance to pull-out stresses succeeded by the parallel then the perpendicular samples. Yet, the overall performance of 3D printed concrete in terms of the bond generated with steel could be rated as satisfactory.
Conference Paper
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Layer-by-layer construction of concrete through additive manufacturing allows for greater design freedom in concrete construction compared to conventional casting methods. This has led researchers to pursue a variety of potential system solutions to the enable the creation of architectural-scale additively-manufactured concrete structures. One of the most common approaches is through the extrusion of concrete patterned via a six-axis robotic arm. However, while the use of a six-axis robotic arm can offer significant geometric advantages in the printing of architectural-scale concrete structures, it also suffers from significant challenges that must be addressed. In this paper, the authors discuss potential methods to address such challenges associated with (1) minimizing travel moves in toolpath design, (2) expanding the achievable build volume, and (3) inserting prefabricated components in a structure being printed. These solutions are then demonstrated through the context of NASA's 3D-Printed Habitat Challenge.
Chapter
The smart manufacturing revolution is continuously enabling the manufacturers to achieve their prime goal of producing more and more products with higher quality at a minimum cost. The crucial technologies driving this new era of innovation are machine learning and artificial intelligence. Paving to the advancements in the digitalization of the production and manufacturing industry and with a lot of available data, various machine learning techniques are employed in manufacturing processes. The main aim of implementing the ML techniques being to save time, cost, resources and avoid possible waste generation. This paper presents a systematic review focusing on the application of various machine learning techniques to different manufacturing processes, mainly welding (arc welding, laser welding, gas welding, ultrasonic welding, and friction stir welding), molding (injection molding, liquid composite, and blow molding) machining (turning, milling, drilling, grinding, and finishing), and forming (rolling, extrusion, drawing, incremental forming, and powder forming). Moreover, the paper also reviews the aim, purpose, objectives, and results of various researchers who have applied AI/ML techniques to a wide range of manufacturing processes and applications.
Chapter
In this paper we present a novel reinforcement method for concrete 3D printed elements using fibre winding. This technique, termed Core Winding Reinforcement (CWR), allows for force-flow oriented alignment of fibre reinforcement along the part’s faces. It has been tested in combination with Shotcrete 3D Printing (SC3DP), but is suitable for both, material extrusion and material jetting. The paper describes the fully automated design-to-fabrication workflow for a 1:1 demonstrator using SC3DP: First, the stress distribution of a given wall geometry is analysed digitally, second, the core is printed, third, the reinforcement fibre is wound and fixed onto the core, fourth, it is embedded by applying a cover layer of shotcrete, and finally, the surface is trowelled in an automated manner.
Chapter
Large scale construction 3D Concrete Printing (3DcP) has gained much attention worldwide with the recent developments of many new technologies and proof of concept structures. One inherent limitation in 3DcP is the automatic laying of reinforcement. So far, the methods proposed for integrating vertical reinforcement are rudimentary and involve manual post processes. Majority of 3DcP wall structures overcome this issue by using the printed section as a shell and after hardening involve manual post processes to reinforce the structure. In this paper a new method of reinforcing is introduced termed the Layer Penetration Reinforcing Method (LPRM). This process involves the printing of a predetermined number of layers, then the subsequent penetration of pre-cut reinforcement through the fresh layers. To prove the concept a lab scale wall (300 mm tall) is printed and reinforced with 7 mm deformed steel bar and ×9 mm stainless steel helical bar. The wall is cut into 100 mm × 60 mm × 300 mm beam sections and tested in 3-point bending with the bar sitting a depth of approximately 70 mm to measure the flexural strength. The samples are compared to conventionally reinforced concrete. Results have shown that the printed beams with deformed bar and helical bar increase the flexural strength of the wall by 184% and 142% respectively. Deformed bar proved superior over helical bar in reinforcing a 3DcP section by obtaining a flexural strength 83% that of a conventional reinforced section, compared to 47% for helical bar.
Chapter
In order to fully realize the disruptive nature proposed by concrete printing for the construction industry, key challenges need to be overcome to enable the scaling up of this technology. Chief amongst them is the incorporation of reinforcement to absorb tensile stresses and support the structure not only during the printing and curing but also during its service life. Numerous strategies have been tested that allow for embedding reinforcement in the form of filaments, cables, rods or mesh during and/or post printing. This paper explores a strategy for in-situ printing that attempts to embed discrete U-shaped reinforcement elements “staples” vertically interlocking layers simultaneously while printing. A tool, developed for this purpose, trails the extruder and discharges a reinforcement staple that embeds itself into the printed layers. The staples not only penetrate multiple layers, but also interlock to form a reinforcement matrix in the concrete along the vertical axis capable of absorbing limited amounts of tensile stresses. When subject to a 3-point bending test, the reinforced printed elements exhibited an increase in tensile properties. Nevertheless, further research into shape and size of the reinforcement staple is needed to achieve optimum results. Furthermore, with the assistance of robotic fabrication strategies, every position within the print geometry can be identified accurately and reinforcement can be positioned precisely. These positions and their properties/states can be informed by simulating the performance of the geometry under load conditions. The ability to place reinforcement discreetly and accurately can help localize the reinforcement to key stress areas within the geometry thereby optimizing its performance and the use of material.
Chapter
Additive manufacturing (AM) or 3D printing is a rapid prototyping process that has captured the attention of architects and designers worldwide in the last few years. Multiple research groups and commercial entities are exploring different areas of 3D concrete printing (3DCP) with one of the main topics being the potential to improve the design freedom, while simultaneously achieving sufficient structural ductility. Based on the target design impression of a free form 3DCP structure, this study presents a number of 3DCP strategies to print arbitrary double-curved geometries with improved concrete ductility. A digital design-to-fabrication workflow was applied, consisting of defining parameters at various stages of the process. Two case study objects have been printed, both featuring double-curved surfaces achieved through cantilevered printing with support material, and by printing on a curved support surface, respectively. The former object acted as support for the latter. Entrained cables and secondarily added glass fibres were used to obtain ductility. The result is a double-curved 1 \(\times \) 1 m panel with fibre-reinforced printed concrete, as well as a double curved print bed, reinforced with high strength steel cables.
Article
Ordinary electromagnetic wave-absorbing concrete can substantially reduce electronic pollution but usually has limited EMW-reflecting capacity. Thus, EMW-absorbing macrostructure can be applied to further reduce EMWs. These concrete macrostructures could be manufactured using 3D cementitious printing technology as conventional casting methodology is not sufficient in standard manufacturing. However, many printed concretes may demonstrate inferior mechanical performance to that of the cast counterpart due to improper fabrication procedure. Therefore, the present study demonstrates the mechanical capacity improvement of EMW-absorbing concrete through optimizing chemical additive and printing parameters. EMW-absorbing experiment confirms that 3D printing technology using enhancement methodology enhances the microwave absorption. Mechanical results show that the hydration velocity as well as the hydration degree acceleration for the printed sample are improved. The compressive strength of the printed samples is improved by 9% and 40% at 28 days and 7 days, respectively. The mercury intrusion porosimetry test indicates that 3D printing provides a favorable squeezing effect to decrease concrete porosity, reducing the void fraction from 17.47% to 11.13% and narrowing the medium void size distribution from 48 nm to 22 nm. To this end, the proposed enhancement methods improve the mechanical and EM absorbing behavior of 3D-printed elements.
Article
Extrusion three-dimensional (3D) concrete printing (3DcP) is an automated construction technology that involves the layer-by-layer deposition of stiff concrete to build a structure without formworks. The interlayer strength is compromised by weak bonds and lack of vertical reinforcements. The bar-penetration technique is a 3DcP reinforcement method where reinforcing bar is inserted vertically through freshly printed layers. Application of a cement paste to the bar during penetration has proven to increase the bar to matrix bond. To be effective as continuous reinforcement, a sequential vertical lapping of bars is considered. For this method to be effective, an understanding of minimum lap length in 3DcP requirements is crucial. This study investigates center- and off-center-lapped samples with lap lengths of 20, 17, 14, and 11 times the bar diameter, subjected to three-point bending tests. Failure modes and crack patterns were recorded and compared with single-bar-penetrated samples. Results and findings were further validated by the printing and testing of a large-scale wall section. Comparisons with small scale results and design calculations showed promising structural performance.
Article
3D printing of cementitious materials is gaining attention in the construction industry. However, convenient methods are needed for integrating reinforcement into 3D-printed concrete. This paper demonstrates the mechanical enhancement offered by a novel form of mortar–polymer laminar composite. The polymer reinforcement is itself extrusion 3D-printed as lattice-like sheets, which are interlaced with mortar layers in a manufacturing process that is compatible with rapid and robotic construction. Displacement-controlled compression tests were carried out on three different composites. One of these was made with normal mortar, while two had added waste material components: biochar or fly ash. Polymer reinforcement increased the overall ductility of all composites that were cured in air-dry condition—the relevant condition for material printed on-site. These ductility improvements were seen even though the addition of the polymer decreased the overall peak compressive stress in all but one case. When mortars contained either biochar or fly ash, incorporating plastic reinforcement provided similar ductility to reinforced mortar without these waste materials. On the other hand, introducing biochar to unreinforced mortar reduced its ductility appreciably. The demonstrated composites may therefore enable increased use of waste materials in cement mixtures for building construction.
Article
de Mit extrusionsbasierten 3D‐Druckmethoden herstellbare unbewehrte Betonbauteile sind nur in seltenen Fällen für den Einsatz in realen Bauwerken geeignet, da sie spröde versagen und unzureichende Tragfähigkeiten aufweisen. Daher werden neue Verfahren benötigt, die die Integration von Stahlbewehrung in den Betondruckprozess und damit die additive Fertigung des Verbundwerkstoffs Stahlbeton ermöglichen. Die Konzeptionierung eines praxisorientierten 3D‐Druckverfahrens für Stahlbeton, das sog. „Additive Manufacturing of Reinforced Concrete“ (AMoRC), ist daher Gegenstand des vorliegenden Beitrags. Im AMoRC‐Verfahren werden konfektionierte Stahlbewehrungsstäbe abschnittweise mit einem Lichtbogenbolzenschweißverfahren zu einer dreidimensionalen Bewehrungsstruktur gefügt und simultan mit einem Beton‐Extrusionsprozess umdruckt. Der vorliegende Beitrag beschreibt die Entwicklung des Verfahrens und erste Voruntersuchungen zur Umsetzbarkeit. Abstract en Conception of a real world 3D printing method for reinforced concrete (AMoRC) 3D printed plain concrete components (without reinforcement) produced through extrusion‐based 3D printing methods are rarely suitable for use in real structures because they fail brittle and have insufficient structural resistance. Therefore, new methods are needed that allow the integration of steel reinforcement into the concrete printing process and thus the additive production of the composite material reinforced concrete. The conceptual design of a practice‐oriented 3D printing process for reinforced concrete, the so‐called Additive Manufacturing of Reinforced Concrete (AMoRC), is therefore the subject of the present paper. In the AMoRC process, segmented steel reinforcing bars are joined to form a three‐dimensional reinforcement mesh using an arc stud welding process and simultaneously overprinted with a concrete extrusion process. This article describes the development of the process and preliminary investigations on its feasibility.
Chapter
The need for methods for forming concrete has existed for as long as concrete has been used in constructing the built environment. Creating flat, rectilinear formers have traditionally been the cost and time efficient default for the majority of applications. The desire for greater design freedom and the drive to automate construction manufacturing is providing a platform for the continued development of a family of processes called Digital Fabrication with Concrete (DFC) technologies. DFC technologies are many and varied. Much of the material science theory is common, but the process steps vary significantly between methods, creating challenges as we look towards performance comparison and standardisation. Presented here is a framework to help identify and describe process differences and a showcase of DFC application case studies that explain the processes behind a sub-set of the technologies available.
Article
Extrusion based 3D concrete printing is an emerging construction automation technology. A major challenge is an automated ‘in-process’ reinforcing method while 3D printing. This study presents an effective in-process reinforcing technique by penetrating deformed reinforcing bars through a predefined number of freshly printed layers. The bond varies along the penetration depth due to differing levels of disturbances experienced by the layers due to the penetrated bar. To characterise the bond at different depths, pull out tests are performed on sections of a 350 mm bar penetrated through a printed wall. The results are then compared to a separate sample on a sand bed with varying lengths of bar penetrated through. The sand bed method was used to isolate the effect of damage due to penetration action. It was found that penetrations over 90 mm caused significant damage. The bond mechanism is investigated and explained with supportive evidences.
Article
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This work explores additive manufacturing (AM) of concrete by using a six-axis robotic arm and its use in large-scale, autonomous concrete construction. Concrete AM uses an extrusion method to deposit concrete beads in layers to create a three-dimensional (3D) shape. This method has been found to have many uses and advantages in construction applications. The lack of formwork and autonomous nature of this manufacturing method allows for new geometries and materials to be printed in unsafe or challenging environments. Autonomous construction has been suggested as a method of creating habitats in rapid-response scenarios. This article discusses research toward one such system that could be used to rapidly construct necessary habitats in response to low-resource and emergency situations. This required addressing certain limitations of a six-axis robotic arm platform along with overcoming system challenges to achieve deliverables for NASA's “3D Printed Habitat Challenge.” This included system design to increase the build volume, integrate embedding, print non-coplanar sections, and minimize travel moves to address the challenges associated with continuous extrusion of cementitious material. The system was demonstrated by printing a one-third scale habitat, which represents the first 3d-printed fully enclosed structure at an architectural scale without the use of support.
Article
Electromagnetic wave (EMW) pollution negatively impacts information, equipment security, and the human body. However, neither powder phase absorbent nor ferrite fiber using traditional casting methodology cannot form electromagnetic superstructure to flexibly enhance EMW absorbing capacity. Thereby, ferrite fiber absorbent in well-oriented manner by 3D printing can be a feasible solution in EMW absorption due to its structural EMW anisotropy property. In this study, the influence of EMW superstructures using 3D-printed oriented copper fiber upon microwave reflectivity is investigated, and an equivalent waveguide attenuator model is proposed. First, an EMW-absorbing composite containing 6 wt% copper powder and 25 wt% copper slag is prepared. In copper slag cementitious composite, copper fiber (CF) and steel fiber (SF) are incorporated at 0.5 wt% separately. In each group, EMW-absorbing elements are manufactured through casting, laminar parallel printing, and cross printing. The superstructure anisotropy and EMW absorption performance are investigated through a network analyzer. The cross superstructure is outstanding in low-frequency absorption, while the parallel superstructure demonstrates desirable reflectivity at a high-frequency range. The copper fiber-reinforced element produced through crossed printing is determined as the optimized configuration, reaching a −20.43 dB reflectivity peak with an 11.79 GHz bandwidth. Lastly, an equivalent waveguide attenuator model is proposed to explain the superposition enhancement of the dielectric property, space impedance matching, and multiple scattering.
Article
3D-printed construction allows elaborating building elements with diverse shapes that are digitally controlled. This paper exposes the modeling of 3D-printed curved walls through parametric programming in building information modeling (BIM) in order to support a cost-efficient building design. The advantage of using curved walls is based on the possibility of reducing their thickness with respect to straight walls of similar length given their higher resistance to overturning forces. The programming developed here can propose a considerable set of solutions using curved walls for a rectangular enclosure of dimensions given by the user. A case study for a vehicle sale pavilion is shown, for which a set of 1,600 solutions with curved walls of different curvature angles and lengths is generated and subsequently analyzed. From this analysis, those models with lower material consumption and execution time are selected to be more thoroughly studied in the design process. Thus, a novel strategy is provided to researchers and practitioners for developing more efficient and expressive building designs based on 3D-printed construction. The most efficient solution identified in the example reduces material consumption by 61%, with an estimated cost saving of 53%.
Article
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Additive manufacturing in construction is beginning to move from an architect's modelling tool to delivering full-scale architectural components and elements of buildings such as walls and facades. This paper discusses large-scale additive manufacturing processes that have been applied in the construction and architecture arena and focuses on ‘Concrete Printing’, an automated extrusion based process. The wet properties of the material are critical to the success of manufacture and a number of new criteria have been developed to classify these process specific parameters. These criteria are introduced and key challenges that face construction scale additive manufacturing are presented.
Article
Additive manufacturing is gaining ground in the construction industry. The potential to improve on current construction methods is significant. One of such methods being explored currently, both in academia and in construction practice, is the additive manufacturing of concrete (AMoC). Albeit a steadily growing number of researchers and private enterprises active in this field, AMoC is still in its infancy. Different variants in this family of manufacturing methods are being developed and improved continuously. Fundamental scientific understanding of the relations between design, material, process, and product is being explored. The collective body of work in that area is still very limited. After sketching the potential of AMoC for construction, this paper introduces the variants of AMoC under development around the globe and goes on to describe one of these in detail, the 3D Concrete Printing (3DCP) facility of the Eindhoven University of Technology. It is compared to other AMoC methods as well as to 3D printing in general. Subsequently, the paper will address the characteristics of 3DCP product geometry and structure, and discuss issues on parameter relations and experimental research. Finally, it will present the primary obstacles that stand between the potential of 3DCP and large-scale application in practice, and discuss the expected evolution of AMoC in general.