No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
3D Printing Concrete with Reinforcement
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.
... The implementation of this process was demonstrated with the first printed house in Germany in Beckum [18]. However, the integration of the reinforcement and the rheological adjustment of the concrete mixtures remain a major challenge, especially for on-site concrete constructions [19][20][21]. The extrusion process has great potential for the serial production of thin, reinforced, highperformance concrete elements. ...
... One key research direction within the 3D concrete printing community, is the integration of reinforcement [20,21,167]. Microfibers are added to the mixture during mixing or continuous fibers are integrated into the printed strand. ...
... On the one hand, it must be conveyable within the extruder and, on the other hand, it must have the desired shape and thus a sufficient green strength after leaving the mouthpiece [23]. In [20] various fibres were investigated in combination with the extrusion process The results show that both PVA and basalt fibres are generally suitable for concrete extrusion. However the use of aramid fibres resulted in deterioration of the concrete consistency due to their high water absorption thus, a defect-free extrusion was not possible. ...
One of the main challenges in concrete construction at present is the reduction of CO2 emissions. To achieve this, both academia and industry are testing innovative methods, developing CO2-reduced materials, and implementing design principles. CO2-reduced materials are being developed and construction principles are being implemented. In addition to the development of new resource-saving construction materials, innovative manufacturing processes such as additive manufacturing are being tested to use the materials only where they are needed. One promising approach is the use of textile reinforced concrete, which uses woven glass, basalt, aramid or carbon fibres that have a much higher tensile strength than conventional structural steel. As a chemically inert material, carbon fibres offer the additional advantage of being insensitive to corrosion and are therefore particularly suitable for the realisation of durable, material-saving high-performance concrete elements. The extrusion process is an innovative method for implementing new construction concepts from carbon reinforced concrete. In this process, solid to viscous materials are transported through an extruder and pressed through a shaping mouthpiece. This enables the efficient production of precise linear components without the need for formwork. Initial approaches to integrating flexibly impregnated textiles in a laboratory extruder were already carried out in 2012 at the Institute of Building Materials Research at RWTH Aachen University (ibac). However, for the implementation of high-performance textile reinforced concrete components with subsequent longitudinal and transversal shaping with a laboratory extruder, scientifc fundamentals and methods are lacking. In this work, the state of the art of textile reinforced concrete, concrete extrusion and form optimised constructions is presented first. It is followed by four papers in which the scientific research and methods developed in the context of this work are presented. Chapter 2 presents the basic principles for the development of an innovative mouthpiece that allows the integration of arbitrarily stiff impregnated textiles in the concrete extrusion process. Chapter 3 describes the development of a test method used to accurately describe concrete mixtures prior to actual extrusion in order to predict defect-free extrusion in LabMorTex. In Chapter 4, the shaping behaviour of the (un)reinforced, microfiber- and textile reinforced concrete after extrusion is investigated. The aim of the investigations is to identify the technical limits of longitudinal and transverse shaping for the implementation of material-minimised structures. Chapter 5 describes the design and Chapter 6 the implementation of an innovative wall / slab element assembled from extruded textile reinforced components. In addition, the slab element is compared with an equivalent reinforced concrete system of the same dimensions and the same flexural strength in terms of sustainability and structural design. The aim of the study is to implement the findings obtained in Chapters 2–4 in an exemplary building component.Finally, chapter 6.3 presents and discusses the results of the durability study of the extruded concrete.
... 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]. ...
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] ...
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.
... Nowadays, reinforced concrete is used in masses and is associated with various environmental concerns and geometric restrictions, leading to increasing demand for technological developments in 3D concrete printing [40,41]. To elaborate, the greatest obstacle to utilizing 3DCP is an effective reinforcement method that would ensure structural integrity and optimize the load-bearing capacity of 3D concrete-printed structures [40][41][42][43]. ...
... Nowadays, reinforced concrete is used in masses and is associated with various environmental concerns and geometric restrictions, leading to increasing demand for technological developments in 3D concrete printing [40,41]. To elaborate, the greatest obstacle to utilizing 3DCP is an effective reinforcement method that would ensure structural integrity and optimize the load-bearing capacity of 3D concrete-printed structures [40][41][42][43]. Thus, researchers have been studying and exploring the feasibility of constructing reinforced 3D concrete-printed buildings using different materials and methods. ...
The technology of additive manufacturing, especially 3D concrete printing (3DCP), has been recently adopted in the construction industry as a viable alternative to traditional construction methods. Although the technology offers a wide variety of structural, economic, and environmental benefits, it is still restricted in use due to certain limitations that are still under research. This paper explains the fundamentals of the 3D printing process, its potential, challenges, as well as the different 3D printing systems. The recent literature is explored for recommended materials that possess the required properties for 3D printing, as well as reinforcement methods and techniques. This paper also reviews 3D printing extrusion using concrete and foam and explores the effect of both materials and extruding systems on the final product. The application of different additive construction systems with Building Information Modeling (BIM)-integrated algorithms are also discussed in this paper. It is believed that with providing a comprehensive knowledge of 3D printing for concrete construction, there is a huge potential to change the way cementitious materials are formulated and sustainability aspects are implemented, especially for complicated designs.
... 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]. ...
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.
... 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. ...
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.
... 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 ...
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.
... За последние несколько десятилетий большое распространение получили аддитивные технологии для изготовления изделий и конструкций различного функционального назначения. Наиболее широко данный способ применяется в медицине [1][2][3], аэрокосмической, авиационной и автомобильной промышленности [4][5][6][7], электротехнике [8,9], строительной отрасли [10][11][12][13][14][15][16]. ...
Introduction. The additive manufacturing method implies the emergence of emergent properties in the final product, not inherent in the original elements of the system individually. Performance properties of products obtained by FDM-printing are defined not only by the material properties, but also by printing parameters — nozzle and table temperature, layer thickness, printing speed, the direction of laying layers, their relative positioning, etc. Thus, when designing 3D-printed polymer products with the required characteristics one should consider the material – printing parameters system together. The results of the study of the effect of sorption characteristics of 3D-printed PETG plastic samples made by FDM-printing on their elastic-strength properties are presented. Materials and methods. Three groups of FDM-printed PETG 3D specimens were studied. Collection, preprocessing, analysis, statistical processing and visualization of the data were performed using Python programming language in an interactive Jupyter Notebook development environment. Results. It was found that the moisture content of 3D-printed polymer samples could be conventionally divided into the superstructural and microstructural levels. A comparison of moisture content limits in different moisture saturation conditions shows that the former exceeds the latter by 2 to 6 times depending on the specimen printing parameters. Moisture content of superstructure level has no statistically significant (for α = 0.01) effect on the ultimate tensile strength of the samples, regardless of the printing parameters of the samples. The moisture sorbed by the level of substructure presumably can act as a stress concentrator preventing the free flow of specimens beyond the ultimate tensile strength, which is reflected in the reduction of elongation at rupture. Conclusions. The obtained results allow taking into account the influence of moisture state on the elastic-strength properties of 3D printed articles and structures on the basis of PETG-plastics. This, in its turn, contributes to more accurate prediction of their behavior under real operating conditions.
... Most structural applications require the use of reinforcement to withstand tensile forces and introduce structural ductility [12][13][14][15]. However, the introduction of reinforcement with 3DCP has never been an easy task, and difficulties were recognized at early stages of the technology [4] and various design solutions have been tested in practice to either circumvent the need for reinforcement or integrate reinforcement after the concrete is printed [16][17][18][19][20]. As a result, several reinforcement techniques have been proposed, such as bar reinforcement [21], micro-cable reinforcement [22,23], fiber reinforcement into the cementitious material [24][25][26], steel reinforcement using robotic arc welding [27,28], and in-process mesh reinforcement [29]. ...
A challenge for 3D Concrete Printing is to incorporate reinforcement bars without compromising the concrete-rebar bonding. In this paper, a Computational Fluid Dynamics (CFD) model is used to analyze the deposition of concrete around pre-installed rebars. The concrete is modelled with a yield-stress dependent elasto-viscoplastic constitutive model. The simulated cross-sections of the deposited layers are compared with experiments under different configurations and rebar sizes, and found capable of capturing the air void formation with high accuracy. This proves model robustness and provides a tool for running digital experiments prior to full-scale tests. Additionally, the model is employed to conduct a parametric study under three different rebar-configurations: i) no-rebar; ii) horizontal rebar; and iii) cross-shaped (horizontal and vertical) rebars. The results illustrate that air voids can be eliminated in all investigated cases by changing the toolpath, process parameters, and rebar joint geometry, which emphasizes the great potential of the digital model.
... For all these reasons, the 3D concrete printing of structural applications has been limited to vertical columns or walls [10,11], with the addition of reinforcement steel elements [12], or as lost formwork (outer shell) for concrete casting [13]. In other cases, 3D-concreteprinted components have been used as secondary structural elements of pedestrian bridges, whose main structure is made of steel components, or post-tensioned with printed layers not orthogonal to the flow of forces [14,15]. ...
This paper describes the structural design and engineering of "Striatus", a 3D-concrete-printed unreinforced masonry pedestrian bridge built in Venice in 2021 as part of the Time Space Existence exhibition organised by the European Cultural Centre. The project combines the latest developments in 3D concrete printing with the structural principles of historic unreinforced masonry. Typically, the structural applications of 3D concrete printing are limited to elements such as columns and walls loaded vertically, perpendicularly to the horizontal printing layers, to formwork elements or secondary structural elements. Indeed, fabrication constraints, delamination issues and the low tensile strength of the concrete have been seen as limiting factors to 3D concrete printing for structural applications demanding resistance to bending or predominant loading directions not perpendicular to the printing layers. By using unreinforced-masonry structural principles, this paper shows that structural elements spanning space horizontally, such as a pedestrian bridge, can be built by using the 3D concrete printing components as the main structure, working only in compression, loaded perpendicularly to the printed layers. Furthermore, as a compression-only structure following masonry principles, Striatus enabled the use of unreinforced concrete without any mechanical or chemical connections between the elements and the separation of concrete and steel, only used for the supports and to equilibrate the horizontal thrust of the arch effect through the tension ties. This work shows how the application of unreinforced masonry principles to 3D concrete printing offers new opportunities in terms of structural design and represents a strategy to increase sustainability by reducing material consumption and allowing reusability and recyclability of the structure. Finally, this paper discusses the critical aspects related to the design of Striatus from an engineering and construction point of view.
... Until now, several attempts were tried to integrate the reinforcement in the printing process. Based on the sequence of adding reinforcement, it could be classified as (1) printing or placing reinforcement in advance in the formwork before casting, e.g., Digital Casting System in ETH Zurich [7], or Shotcrete 3D Printing in TU Braunschweig [8]; (2) adding reinforcement simultaneously to the concrete printing, e.g., integrating fibre or textile reinforcement in the concrete extrusion process, which allows for reinforcement parallel to the extrusion direction [9]; (3) adding reinforcement after the printing process, such as Contour Crafting method that firstly printing the external concrete contour as a lost formwork and then post-install the reinforcement in the contour which is subsequently filled with concrete [1]. A more detailed overview over the most important concepts for the integration of reinforcement and their review can be found in [10]. ...
In this paper, a novel 3D printing process for reinforced concrete structures called Additive Manufacturing of Reinforced Concrete (AMoRC) is proposed. The process consists of a continuous concrete extrusion process and an intermittent stud welding process, both carried out by a robotic arm respectively. The welding robot runs ahead of the concrete extrusion robot and produces the spatial reinforcement mesh from prefabricated reinforcing bar segments. A novel fork-shaped print head with four adjustable nozzles allows for concrete extrusion around the reinforcement with different diameters. By joining segmented rebars of limited length to a reinforcement mesh in the AMoRC process, the consumption of energy and time can drastically be reduced compared to shape welding. The length of the joined rebars can be adapted to the component geometry and the extrusion speed. The bar segments to be joined are kept ready in a magazine belonging to the print head, which enables the feeding of bars with different diameters to arrange a load-efficient and economical reinforcement mesh. The preliminary testing of the additively fabricated reinforced concrete components is also implemented to characterize the structural behaviour of those 3D-printed composite specimens. In the initial phase, the reinforcement installation was performed manually until the second robot will be added to the process and experiments were done to characterize the printed structures. The pull-out test is used to investigate the bonding behavior between reinforcement and printed concrete. The four-point bending test is also utilized to study the mechanical behavior of the printed reinforced concrete specimen in a larger scale.Keywords3D-printing of reinforced concreteAMoRC methodcharacterisation methodspull-out test4-point bending experiment
... During the 3D printing process, the steel cables are embedded into the printing layers simultaneously, along with the printing of the layers using a reinforcement entrainment device (RED) (Bos et al., 2017a). A study on the direct entrainment of cable reinforcement into concrete 3D printed elements is done by researchers (Bos et al., 2017b). A device is developed consisting of a spool with a servo-driven motor that inserts cable reinforcement directly before the mix leaves the print nozzle. ...
Concrete 3D Printing (3DP) is a potential technology for increasing automation and introducing digital fabrication in the construction industry. Concrete 3D Printing provides a significant advantage over conventional or precast methods, such as the prospects of topologically optimized designs and integrating functional components within the structural volume of the building components. Many previous studies have compiled state-of-art studies in design parameters, mix properties, robotic technologies, and reinforcement strategies in 3D printed elements. However, there is no literature review on using concrete 3D Printing technology to fabricate structural load-carrying elements and systems. As concrete 3DP is shifting towards a large-scale construction technology paradigm, it is essential to understand the current studies on structural members and focus on future studies to improve further. A systematic literature review process is adopted in this study, where relevant publications are searched and analyzed to answer a set of well-defined research questions. The review is structured by categorizing the publications based on issues/problems associated with structural members and the recent technology solutions developed. It gives an overall view of the studies, which is still in its nascent stage, and the areas which require future focus on 3D printing technology in large-scale construction projects.
... Therefore, the integration of reinforcement has to be considered, and it has to be distinguished from masonry-like 3D printed and reinforced concrete-type structures. Ongoing research examines the integration of reinforcement into 3D printed concrete elements [6][7][8][9][10]. Various integration methods and materials are used to reinforce the printed components. ...
Traditional reinforcement cages are manufactured in a handicraft manner and do not use the full potential of the material, nor can they map from optimised geometries. The shown research is focused on robotically-manufactured, structurally-optimised reinforcement structures which are prefabricated and can be encased by concrete through SC3DP in a combined process. Based on the reinforcement concept of "reinforcement supports concrete," the prefabricated cages support the concrete during application in a combined AM process. To demonstrate the huge potential of combined AM processes based on the SC3DP and WAAM techniques (for example, the manufacturing of individualized CPS), the so-called FLOWall is presented here. First, the form-finding process for the FLOWall concept based on fluid dynamic simulation is explained. For this, a three-step strategy is presented, which consists of (i) the 3D modelling of the element, (ii) the force-flow analysis, and (iii) the structural validation in a computational fluid dynamics software. From the finalized design, the printing phase is divided into two steps, one for the WAAM reinforcement and one for the SC3DP wall. The final result provides a good example of efficient integration of two different printing techniques to create a new generation of freeform coastline protection structures.
... 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. ...
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.
... 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]. ...
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.
... • 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. ...
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.
... 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]. ...
In the era of automation and artificial intelligence, the world is changing rapidly under the broad vision of Industry 4.0. In this framework, the building and construction industry is getting significant attention from both academia and industries with the advent of additive manufacturing technology. Additive manufacturing or 3D printing of concrete provides a complete digital solution to conventional construction practice and fosters sustainable, smart, and green building concepts. In this paper, some recent experimental research conducted at the Indian Institute of Technology Guwahati (IITG) on 3D concrete printing is presented. A custom-developed 3D printable cementitious mix was processed, and its rheological properties were measured using flow table and vane shear apparatus. The influence of process parameters such as print speed and extrusion speed on filament quality (shape retention surface finish) was studied using a lab-scale gantry 3D concrete printer. Finally, the letters of IITG were printed to demonstrate the proposed process parameters and mix design are suitable in practice.KeywordAdditive manufacturingDigital concreteRheologySustainability
... 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 rising interest in 3D-printing of concrete structures for use in marine environments requires development of concrete mixtures with adequate mechanical and durability characteristics. The incorporation of alternative cementitious materials, combined with careful selection of printing parameters has emerged as an effective way of controlling not only the fresh properties and printability of mixtures, but also their mechanical and durability properties. This paper presents the results of various durability related tests performed on 3D-printed mortars, including density, porosity, rate of water absorption and resistance to chloride penetration. Results of these tests indicate that the performance of mortar elements 3D-printed using controlled overlap process was similar to the performance of conventionally cast mortar elements with the same composition. Moreover, the results of the chloride transport related tests obtained from all specimens evaluated during the course of the study indicate low chloride ion penetrability, thus re-affirming that combination of the proposed material and 3D-printing method of fabrication have a potential for producing structural elements for applications in marine environments.Keywords3D-printed concreteDurabilityCorrosionChloridesAbsorption
... 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]. ...
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.
... 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]. ...
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.
... 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. ...
... 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]. ...
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.
... 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. ...
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.
... 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). ...
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.
... 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 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. ...
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.
... 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. ...
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.
... 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]. ...
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.
... 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. ...
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.
... 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]. ...
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.
... 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. ...
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.
Volume 24A provides a comprehensive review of additive manufacturing (AM) design fundamentals and applications. The primary focus of the Volume is on metallic systems with limited emphasis on polymers and ceramics where applicable. The first five divisions provide an in-depth review of each of the key aspects of the entire AM value chain. The materials/process development division discusses AM process-structure-property relationships, process optimization and defects, and material/process modeling. The design principles division includes coverage of design rules, part consolidation and assemblies, and simulation-driven design. In the data management division, data analytics, data security, and data sharing through a common data model are discussed. Next, the mechanical property division section includes discussion on fatigue, tensile, hardness, and other property testing. The AM non-destructive evaluation (NDE) division discusses surface and geometrical characterization, ultrasonic testing, radiography, computed tomography, and resonant ultrasound spectroscopy. Included in the AM in-situ process control and monitoring division are articles on machine learning for anomaly detection, in-process thermography, laser powder-bed fusion process control, and in-situ x-ray imaging. The applications division reviews key sectors that are embracing and adopting AM technologies. The market sectors are aviation, space flight, medical, automotive, oil and gas, construction, energy, and electronics. The last two divisions cover AM standards, qualification, and certification, as well as environmental, economic, and business concerns.
Digital fabrication, including construction of buildings with use of 3D printers is gaining significant momentum for the construction sector. Benefits such as free form architecture, reduction of building time, labor costs and waste material, freedom of geometry can be taken advantage in such building techniques. 3D Printing Concrete (3DCP) is a wet manufacturing process where layers of extruded mortar are bound by successive material deposition. Most common equipment for this type of application are the gantry printers, which are based on the cartesian robotic systems technology. 3BUILD is the research project, co-funded by the “Ereyno-Dimiourgo-Kainotomo” program by the Greek Ministry of Development, with participation from TITAN, SIKA, COS and NTUA. The project main objective is the design and construction of a gantry type 3D printer and furthermore the use of the printer for the construction of a structure of dimensions up to 8 × 8 × 3 m. Development of works for the certain project included the design and construction of a middle-sized printer and printing of 2 m high structures of various shapes, investigation of sensitivities of mortar properties to different printing parameters (printing speed, printing geometry, layer dimensions) and relevant adjustments, the design and final construction of the full scale 3D printer and all challenges encountered and resolved before finally printing in real scale.Keywords3D printinggantry printerconcretemortar3BUILD
This study demonstrates and experimentally evaluates a novel reinforcement strategy capable of rapidly bridging the interlayer interface in printed concrete. Modified male-female blind rivets and flexible stainless-steel wire ropes are proposed as orthogonal and longitudinal reinforcement, respectively. To investigate the proposed orthogonal reinforcement, the displacement of a rivet strand during the fastening process is analysed through digital image correlation to compare two different nosepieces attached to a riveting tool. Additionally, the compressive force exerted on a strand and the time elapsed during fastening are evaluated. Tensile force-displacement, elasticity and yield strength responses are presented for rivet strands and rope samples. Four-point flexural tests are conducted on orthogonally reinforced printed prisms and compared with unreinforced prisms. Rivet strands are rapidly realised with 0.54 mm average lateral displacement when a novel nosepiece, specifically developed in this research, is attached to the pneumatic riveting tool. Further, a rivet-to-rivet connection is made in 0.29 seconds on average. Hardening and ductile behaviour are observed in the tensile results of rivet strands (82 MPa average fracture stress at 1.808% strain) compared to the more consistent but lesser hardening and ductility of the wire ropes (1645 MPa average fracture stress at 1.582% strain). Nevertheless, the flexural performance of the concrete prisms is significantly improved by the addition of the proposed rivet reinforcement, providing hardening behaviour as opposed to the softening behaviour exhibited by the unreinforced control group, resulting in a 230% average increase in the elastic moment capacity.
In construction, additive manufacturing (AM) can be used to create structural or non-structural elements such as frameworks, reinforcement, or panels. However, AM technology still requires enhancements in terms of mechanical response of final 3D-printed elements to accommodate the mechanical needs of structural components. This paper evaluates various AM process parameters and bioinspired printing patterns as a means to improve the mechanical performance of 3D-printed polymeric elements. AM processes, including printing speed and nozzle diameter, are studied. Bioinspired patterns, including Bouligand-like, alternating, sinusoidal, grid, triangular, and hexagonal, are investigated and compared to simple parallel pattern. Results of this study suggest that mechanical behavior of 3D printed elements can be significantly enhanced by optimizing the printing speed and nozzle diameter. Incorporating bioinspired architectures in AM such as Bouligand pattern are shown to enhance the mechanical performance. Slower speeds and larger nozzle diameters result in higher tensile strength. Continuous and twisting patterns yield more ductility, while patterns parallel to the direction of the tensile test result in higher strengths. Microscopic images from the fracture surface indicate that larger nozzle diameter enhances intra- and interlayer bonding between consequent printed layers. Additionally, more complex crack propagation is observed in twisting patterns with enhanced elongation before total failure. It is also observed that there is an optimal time of exposure to high temperature for deposited material during AM to improve bonding between adjacent beads. Bioinspired patterns helped maintain higher ductility with similar strength despite encompassing higher porosity than parallel pattern which could be advantageous for material optimization purposes. The bioinspired 3D printed polymeric elements showed tensile properties higher than those of plain polymer filament. Outcome of this study can help optimize both the process and the architecture of 3D-printed elements to enhance their mechanical properties to be used as reinforcing elements for reinforced concrete applications.
3D printing of cementitious materials or concrete (3DCP) has developed unbelievably in past 10 years and has the potential to revolutionize the concrete industry completely in the couple of incoming decades. Compared to cast concrete, 3DCP technology has a high customizability of architectural and structural design; can reduce material consumption, minimize material waste, decrease construction time from months or days to hours; can improve sustainability, environmental impact and resolve residential crises through providing $10,000 homes. In this article, a comprehensive review for 3D printing of various materials, techniques and trending applications has been carried out. The materials used for 3DCP, mix design principles and printing process parameters has been overviewed. The factors influencing flowability, extrudability, buildability of various mixes; microstructure and mechanical properties of the hardened concrete; and improvement techniques has been discussed. An important part of this review is provided to highlight the cost of 3D printed houses compared with traditional alternatives, and environmental sustainability of 3DCP and its compatibility with international plans for climate change and minimizing the energy usage. Finally, some to-date challenges are discussed, with conclusions that also identifies the needed research and state of the art for this incredible technology. Overall, this review presents the finding of the mentioned topics through exploring 396 of the latest published articles especially focusing on last three years.
Voids and gaps surrounding reinforcements are of urgent concern for the reinforcing techniques of 3D printed concrete. This study proposed a cast-in-process technique to fabricate reinforcements during the printing process. The experimental investigations were conducted by grouting epoxy resins into reserved tunnels in cast and printed beams. The grouted epoxy was cured as reinforcements with close contact with the hardened concrete. Smooth interfaces were generated in cast concrete beams owing to the compaction and vibration. Rough interfaces were obtained between the printed composite and the reinforcements, achieving effective bonding between the interfaces. Visible voids or gaps did not occur. The reinforcements achieved maximum flexural improvements of 156.6% and 83.0% for the printed rectangular- and zigzag-beams. A potential hybrid manufacturing system combining 3D printing and casting-in-situ was then proposed, including the dual-nozzle extrusion principle and material requirements.
The support structures used in additive manufacturing (AM) techniques cause poor surface quality in the contact areas of the support with the printed parts. Thereby, this support structure usage is a critical issue that needs to be controlled for minimizing the printing time and post-processing challenges associated with AM parts. To alleviate the errors due to the support structures, these faceted models can be deposited in multi-direction using multi-axis systems. This paper presents an approach to decompose the design features and detect multiple build directions for certain cases of faceted models to print parts using multi-robots collaborative material extrusion (MRCME) systems developed by the authors. The use of support structures limits the surface finish of as-built 3D printed parts. The objective of this work is to develop a volume decomposition algorithm, which can decompose the part into sub-volumes and identify the build direction of the decomposed sub-volumes. The build direction is found from the geometric reasoning of the concave and convex loop centroids. Initial decomposition is done with the concave–convex loop pair relationship, and further regrouping is done with the bounding box of the identified pair of concave and convex loops in that particular build direction. The work presented in this paper would help process planning systems to automatically determine Multi-Directional Sub-Volumes (MDSV) and carry out effective part deposition with minimum or no support structures.KeywordsMulti-robots technologyMulti-axis depositionCobotic material extrusionPost-processing
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.
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.
The article at hand presents an approach for analyzing the 3D Concrete Printing (3DCP) by means of the Discrete Element Method (DEM). An advanced user-defined simulation material model for fresh printable concrete has been developed to simulate extrusion, discharge and deposition. In addition, a calibration procedure is shown to find a fitting parameter set for the material model parameters based on experimental data. The calibration of the latter is an iterative adaption process, leading to a realistic representation of real printable concrete. Finally, an extrusion-based 3DCP process is exemplary simulated to show the potential of the simulation method for process analyses and to verify the applicability of the model. The developed simulation tool enables a better understanding of the extrusion process during 3DCP and a profound analysis of the material flow within the extruder. Based on this information, improvements in the machine layout and the process parameter settings can be identified, allowing for further printing process optimizations.Keywords3D concrete printingDigital concreteDiscrete element methodExtrusionCalibration
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.
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.
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.
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.
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.
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.
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.
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.
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.
