Search

The Technical University of Braunschweig (Brunswick) and Technical University of Munich were successful to establish a Collaborative Research Centre called “Additive Manufacturing in Construction (AMC) – The Challenge of Large Scale” starting from 2020 and funded by the German Research Foundation (DFG). The aim of this project is “to create the basic conditions for the introduction of additive manufacturing in construction, and thus to pave the way for the use of resource-efficient constructions with a high level of design freedom”. Surveying engineering (geodetic surveying, photogrammetry, laser scanning and GNSS) plays a major role in one of the sub-projects called “Integration of Additive Manufacturing in the Construction Process”. This paper aims at introducing the large scale AMC with the main focus on investigating the role of surveying engineering in this topic which will be a topic of high interest in the coming years in the digital fabrication within construction field. After a short introduction on additive manufacturing in construction, this paper will present the general aims and structure of the Collaborative Research Centre. Thereupon, the importance of geometric quality inspection and establishing and transferring different coordinate systems during the Additive Manufacturing (AM) construction steps (elements fabrication, installation and whole structure/building control) and the role of geodetic surveying, photogrammetry, laser scanning and GNSS will be outlined. This will be presented within a subproject called “C06: Integration of Additive Manufacturing in the Construction Process” and potentials and challenges for integrating surveying engineering in component and building level additive manufacturing in construction are mentioned.

The Large Particle 3D Concrete Printing (LP3DCP) process presented in this paper is based on the particle bed 3D printing method, here, the integration of significantly larger particles (up to 36 mm) for selective binding using the shotcrete technique is presented. In the LP3DCP process, the integration of large particles, i.e., naturally coarse, crushed or recycled aggregates, reduces the cement volume fraction by more than 50% compared to structures conventionally printed with mortar. Hence, with LP3DCP, the global warming potential, the acidification potential and the total non-renewable primary energy of 3D printed structures can be reduced by approximately 30%. Additionally, the increased proportion of aggregates enables higher compressive strengths than without the coarse aggregates, ranging up to 65 MPa. This article presents fundamental material investigations on particle packing and matrix penetration as well as compressive strength tests and geometry studies. The results of this systematic investigation are presented, and the best set is applied to produce a large-scale demonstrator of one cubic meter of size and complex geometry. Moreover, the demonstrator features reinforcement and subtractive surface processing strategies. Further improvements of the LP3DCP technology as well as construction applications and architectural design potentials are discussed thereafter.

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.

Digital Fabrication with Concrete (DFC) encompasses 3D Concrete Printing (3DCP) and many other methods of production. DFC is emerging from an era of invention and demonstration to one where the merits of one principle over another needs to be quantified systematically. DFC technologies vary in characteristics, complexity and maturity which hampers the synthesis of research and comparisons of performance. The interdependence of design geometry, material properties and process characteristics is well recognised. Materials research has made significant progress in recent years and there have been many applications with varying design geometries demonstrated. Far less has been done to guide the definition and description of the processes used. This work takes a step forward by presenting classification and process description guidance for DFC. The approach was developed by engaging a broad cross-section of the international community through the activities of the RILEM Technical Committee 276 between 2016 and 2020., Cement and Concrete Research, 134, ISSN:0008-8846

Today, the majority of research in 3D concrete printing focuses on one of the three methods: firstly, material extrusion; secondly, particle-bed binding; and thirdly, material jetting. Common to all these technologies is that the material is applied in horizontal layers. In this paper, a novel 3D concrete printing technology is presented which challenges this principle: the so-called Injection 3D Concrete Printing (I3DCP) technology is based on the concept that a fluid material (M1) is robotically injected into a material (M2) with specific rheological properties, causing material M1 to maintain a stable position within material M2. Different to the layered deposition of horizontal strands, intricate concrete structures can be created through printing spatially free trajectories, that are unconstrained by gravitational forces during printing. In this paper, three versions of this method were investigated, described, and evaluated for their potential in construction: A) injecting a fine grain concrete into a non-hardening suspension; B) injecting a non-hardening suspension into a fine grain concrete; and C) injecting a fine grain concrete with specific properties into a fine grain concrete with different properties. In an interdisciplinary research approach, various material combinations were developed and validated through physical experiments. For each of the three versions, first architectural applications were developed and functional prototypes were fabricated. These initial results confirmed both the technological and economic feasibility of the I3DCP process, and demonstrate the potential to further expand the scope of this novel technology.

This paper presents the recent advances in the development of a novel 3D concrete printing technology called Shotcrete 3D Printing (SC3DP). In order to demonstrate the unique assets of this technique a design and fabrication strategy for fully reinforced, double curved concrete demonstrator featuring high surface quality was developed, and is described in detail in this paper. In particular, two topics were highlighted in this demonstrator, firstly the integration of structural reinforcement in both principal directions and secondly an automated surface finishing process for a high-quality concrete surface. This combination of additive fabrication and formative and subtractive postprocessing was demonstrated at the unique large-scale Digital Building Fabrication Laboratory (DBFL) of Technische Universitat Braunschweig. The result of this fabrication experiment, a 2.5 * 2.3 * 0.18 m concrete wall element, is finally discussed in relation to the state of the art in 3D concrete printing.

This paper describes the making of DFAB HOUSE, a multi-technology demonstrator of digital fabrication in architecture, engineering and construction (AEC). While most individual digital fabrication technologies used to build DFAB HOUSE have been presented independently at conferences and in journal articles, this paper describes how, in concert, they amount to an architectural achievement that is more than the sum of its parts. To do this, the paper does three things: it describes the process of conceiving and delivering the overall project; secondly, it highlights challenges in implementation; and finally it discusses the significance of DFAB HOUSE in the context of a rapidly transforming architectural research and practice., Fabricate 2020: Making Resilient Architecture, ISBN:978-1-78735-812-6

While a consensus exists that advanced digital and mechatronic technology is on the cusp of profoundly impacting virtually every manufacturing and industry sector, there are some industries that seem to have profited far less from this ongoing ‘revolution’. One prominent example of this is the construction sector and, in particular, building construction. In this paper, we aim at discussing some of the reasons for this apparent lack, and some reasons why this might change in the near future. We introduce the problem of digital in situ fabrication as both a significant challenge and a huge opportunity. We support the discussion with an example of a robotically-fabricated digital concrete wall. Overall, we find that solving in situ fabrication constitutes an inherently multidisciplinary challenge.

Currently, additive manufacturing in concrete construction can be divided into three main methods: firstly, material extrusion, secondly material spraying, and thirdly particle bed binding, with the material typically being applied in layers. In contrast, Injection 3D Concrete Printing (I3DCP) is based on the concept that a fluid material A is deposited spatially free into a material B with specific rheological properties, keeping material A in a stable position within material B. Thus, in contrast to the layered deposition of horizontal strands, free-form three-dimensional concrete structures can be printed entirely in one piece. In general, three versions of Injection 3D Concrete Printing can be classified: a) injecting a fine-grained concrete into a non-hardening carrier liquid; b) injecting a non-hardening suspension into a fine-grained concrete; c) injecting fine-grained concrete with specific properties into concrete with different properties. This paper focuses on Injection 3D Concrete Printing into a carrier liquid. For a deeper understanding of the underlying physical mechanisms, we carry out experiments that vary the rheological properties of the carrier liquid, the concrete flow rate, and the nozzle displacement velocity. We use a ground limestone suspension as carrier liquids in this study. We investigate the effect of the rheological properties of the carrier liquid on the positional stability of the injected concrete in small-scale print experiments. Based on this, we develop an analytical model that describes the positional stability as a function of the rheological properties. Also, we highlight that the final cross-section of the injected concrete strand is dependent on the concrete flow rate and nozzle velocity. Finally, we present the first reinforced I3DCP-elements and current developments of this novel technology for lightweight space frame structures in concrete construction.

Digital fabrication represents innovative, computer-controlled processes and technologies with the potential to expand the boundaries of conventional construction. Their use in construction is currently restricted to complex and iconic structures, but the growth potential is large. This paper aims to investigate the environmental opportunities of digital fabrication methods, particularly when applied to complex concrete geometries. A case study of a novel robotic additive process that is applied to a wall structure is evaluated with the Life Cycle Assessment (LCA) method. The results of the assessment demonstrate that digital fabrication provides environmental benefits when applied to complex structures. The results also confirm that additional complexity is achieved through digital fabrication without additional environmental costs. This study provides a quantitative argument to position digital fabrication at the beginning of a new era, which is often called the Digital Age in many other disciplines.

The development of novel robotic fabrication technologies in architecture concentrates largely on integrating stationary industrial-type robots into off-site prefabrication processes. By contrast, few enabling robotic technologies exist today that allow robotic fabrication processes to be mobile and implemented directly on building sites. While mobile in situ fabrication offers a large range of architectural potentials, its realization requires to address fundamental challenges. First, the production of large-scale and potentially monolithic structures on-site requires an advanced robotic fabrication system that can fulfill the material, structural- and architectural-related demands associated with it. Second, the poorly structured nature of building sites requires mobile robotic systems to be equipped with advanced sensing and control solutions to contend with uncertain conditions found on-site. The research discussed in this paper addresses both of these subjects. It applies a novel construction system for non-standard reinforced concrete structures, termed Mesh Mould, to explore the fabrication of large-scale and monolithic building structures using a mobile robot on site. It further investigates sensor-integrated adaptive fabrication strategies to achieve the accurate fabrication of such a large-scale structure, and this is done despite prevalent uncertainties related to the building site environment, the mobile robotic system, and the material behavior during fabrication. The results of this research were realized in a slender, doubly curved, reinforced concrete wall at the DFAB HOUSE at NEST. This research demonstrator provides the unique opportunity to present robotic in situ fabrication not merely as a future possibility, but as a reality applied to a tangible construction project.

The research described in this paper is dedicated to the use of continuous fibers as reinforcement for additive manufacturing, particularly using Shotcrete. Composites and in particular fiber reinforced polymers (FRP) are increasingly present in concrete reinforcement. Their corrosion resistance, high tensile strength, low weight, and high flexibility offer an interesting alternative to conventional steel reinforcement, especially with respect to their use in Concrete 3D Printing. This paper presents an initial development of a dynamic robot-based manufacturing process for FRP concrete reinforcement as an innovative way to increase shape freedom and efficiency in concrete construction. The focus here is on prefabricated fiber reinforcement, which is concreted in a subsequent additive process to produce load-bearing components. After the presentation of the fabrication concept for the integration of FRP reinforcement and the state of the art, a requirements analysis regarding the mechanical bonding behavior in concrete is carried out. This is followed by a description of the development of a dynamic fiber winding process and its integration into an automated production system for individualized fiber reinforcement. Next, initial tests for the automated application of concrete by means of Shotcrete 3D Printing are carried out. In addition, an outlook describes further technical development steps and provides an outline of advanced manufacturing concepts for additive concrete manufacturing with integrated fiber reinforcement.

Shotcrete 3D Printing (SC3DP) is a novel robot-guided AM technology developed at Technische Universitat Braunschweig in the environment of the Digital Building Fabrication Laboratory (DBFL). For successful automation, it is crucial to understand and redefine the entire concrete spraying process with all its interdependent parameters. This paper presents the basic principles of the SC3DP technology together with the results of a comparative study on the influence of the two concrete printing techniques extrusion and SC3DP on the interlayer bond strength. In particular, the effect of different time intervals between the deposition of two adjacent layers regarding mechanical properties (bond strength) is investigated. As will be shown, the SC3DP method allows convenient mechanical properties although the printed samples exhibit distinct anisotropies. The reasons are discussed based on investigations of the air void distribution by micro CT and mechanical test results.

Concrete is a highly versatile construction material, not only for the reason that it has excellent properties in terms of structural performance, building physics, availability and price, but also because it can be moulded into virtually any shape regardless of its geometric complexity. However, even though current digital design tools allow to effortlessly design and calculate structures, which are exploiting these properties, this potential remains all too often unrealized. This is due to the fact that geometrically complex concrete structures require expensive, one-of-a kind formwork, which can often not be reused or even recycled. Consequently, the current practice for producing non-standard curvilinear architecture in reinforced concrete is neither ecologically sustainable nor economically feasible for a broader range of architectural typologies. Additive Manufacturing (AM) processes, like 3D printing with concrete, on the other hand, currently struggle with the integration of structural reinforcement, limiting the technique to predominantly compression-loaded applications. This research addresses both issues and proposes Mesh Mould, a robotic fabrication process that unifies concrete formwork and structural reinforcement, and hence potentially reduces formwork waste and construction costs for non-standard reinforced concrete constructions. The development of a fully automated robotic fabrication process involved various research disciplines, including architecture, material science, mechanical engineering, robotics as well as civil engineering. This paper describes the technological developments of the Mesh Mould construction system that were necessary to meet the challenges of 1:1 construction. The results are demonstrated in a final loadbearing structure, the Mesh Mould wall of the DFAB HOUSE on NEST.

In this paper we present a system for the in situ fabrication of a full-scale, load-bearing, and doubly-curved steel reinforced concrete wall. Two complementary vision-based sensing systems provide the feedback necessary to build a 12 meter long steel wire mesh as part of a novel digital building process. The sensing systems provide estimates of the robot pose, referenced to the CAD model of the building site, as well as feedback on the accuracy of the built structure over the course of construction. This second piece of information is used to adapt the building plan to compensate for system inaccuracies and material deformations which occur during buildup. In this way, the structure was successfully built with 98% of the total geometry within 2 centimeters of the designed position. To the best of our knowledge, this is the largest structure which has been built by a mobile robot using solely vision-based sensing., 2018 IEEE International Conference on Robotics and Automation (ICRA), ISBN:978-1-5386-3081-5, ISBN:978-1-5386-3080-8, ISBN:978-1-5386-3082-2

If robots are to be employed in the construction of high-rise structures, logistics and material systems have to be entirely rethought to cater for both their abilities and limitations: robots have limited loading capacity, but greater dexterity than other on-site, automated construction techniques. Here, Norman Hack of ETH Zurich and Willi Viktor Lauer of the Future Cities Laboratory (FCL) at the Singapore-ETH Centre for Global Environmental Sustainability (SEC) describe the research they have undertaken to develop ‘mesh-mould’ as an alternative to conventional formwork.

In the context of the Future Cities Laboratory (FCL) of ETH Zurich, the Professorship for Architecture and Digital Fabrication of Fabio Gramazio and Matthias Kohler has set up a robotic laboratory to investigate the potentials of non-standard robotic fabrication for high rise constructions in Singapore. The high degree of industrialisation of this dominant building typology implies standardisation, simplification and repetition and accounts for the increasing monotony evident in many Asian metropolises. The aim of this research on material systems for robotic construction is to develop a new and competitive construction method that makes full use of the malleable potential of concrete as a building material. A novel, spatial, robotic “weaving” method of a tensile active material that simultaneously acts as the form defining mould, folds two separate aspects of concrete -reinforcement and formwork-into one single robotic fabrication process (see Figure 1). This in-situ process could permit the fabrication of structurally differentiated, spatially articulated and material efficient buildings.

Mass transfer and biological transformation phenomena in the capillary fringe were studied using phenol, salicylic acid, benzenesulfonic acid, and the iodinated X-ray contrast agent iomeprol as model organic compounds and the microorganism strain Pseudomonas fluorescens. Three experimental approaches were used: Batch experiments (uniform water saturation and transport by diffusion), in static columns (with a gradient of water saturation and advective transport in the capillaries) and in a flow-through cell (with a gradient of water saturation and transport by horizontal and vertical flow: 2-dimension flow-through microcosm). The reactors employed for the experiments were filled with quartz sand of defined particle size distribution (dp=200...600 μm, porosity e=0.42). Batch experiments showed that phenol and salicylic acid have a high, whereas benzenesulfonic acid and iomeprol have a quite low potential for biodegradation under aerobic conditions and in a matrix nearly close to water saturation. Batch experiments under anoxic conditions with nitrate as electron acceptor revealed that the biodegradation of the model compounds was lower than under aerobic conditions. Nevertheless, the experiments showed that the moisture content was also responsible for an optimized transport in the liquid phase of a porous medium. Biodegradation in the capillary fringe was found to be influenced by both the moisture content and availability of the dissolved substrate, as seen in static column experiments. The gas-liquid mass transfer of oxygen also played an important role for the biological activity. In static column experiments under aerobic conditions, the highest biodegradation was found in the capillary fringe (e.g. βt/β0 (phenol)=0 after t=6 d) relative to the zone below the water table and unsaturated zone. The highest biodegradation occurred in the flow-through cell experiment where the height of the capillary fringe was largest.

Despite the recent advances in, and the adoption of robotic technologies in the construction industry, the architectural processes which demand a high degree of geometric freedom still remain largely labour intensive and manual. This is due to the inherent difficulties in robotizing the current implementation of such processes coupled with the lack of alternate robotic technologies. A specific example, which is also the focus of this paper, is that of building a steel reinforced concrete structure, with varying curvature or cross-section. This process still remains rather manual and requires extensive support of customized form-work. In this paper, first we describe an alternate novel robotic fabrication process for building steel wire meshes which act as both reinforcement and formwork. The robotization of such a process is discussed with the use of a previously developed mobile robotic system. Based on the specifications derived from the process, design of a novel custom designed robotic end-effector, enabling this process, is detailed. Automation of the full robotic system comprising the mobile robotic system and the robotic end-effector is discussed from simulation to control. Through experimental evaluation of the robotic system, we demonstrate the ability to fully automate the construction of non-standard steel reinforced steel meshes of varying curvature and cell sizes.