3D concrete printing (3DCP) offers a versatile, flexible approach for producing customisable, project-specific components as one-off solutions. This paper explores the use of 3DCP as a circular retrofit strategy to fabricate thermally optimised facade outer skins for reused concrete elements. This work formulates a computational design-to-fabrication workflow for the development of three-wythe printed elements, assessing printability, material quantities, and 2D numerical simulations in THERM, while maintaining a consistent internal topology for fabrication. The approach is tested by simulating and comparing four variants from a benchmark uniform section to a customised design. Thermal transmittance improved from 0.41 W/(m2·K) for the base design to 0.29 W/(m2·K) for the custom variable case, using the same amount of printing material. These findings indicate that performance-driven design can deliver meaningful performance upgrades for reuse and suggest the potential of 3DCP as a key enabler technology to facilitate reuse and advance circularity in the built environment.

3D Concrete Printing (3DCP) enables the manufacturing of complex structures without increasing the costs of the process. However, this increased complexity is limited by conventional design workflows based on boundary representation 3D modelling and conventional slicing methods. While previous research has demonstrated the potential of print paths as a design method for customised structures and surface qualities, their use to generate controlled porosity in 3DCP structures is still unexplored. This paper investigates the use of print patterns at the scale of the printed filament to control the porosity, material distribution, and surface area of 3DPC structures, creating variable porosity and permeability that enhance design flexibility in 3DCP. For this, seven printing patterns were developed and tested to assess the relationship between exposed surface area and material use. The findings demonstrated that alternating patterns could create permeable structures with an extended surface area, which enables the creation of multi-functional structures. This research contributes to extending the design possibilities of 3DCP, allowing the generation of material properties that can be embedded and graded throughout the printed part.

The ReCreate project researches deconstruction and reuse of precast concrete elements, not originally designed for disassembly. Real-life deconstructions of precast concrete buildings in four countries (Finland, Sweden, the Netherlands and Germany), performed by ReCreate’s industrial partners as well as collaborators to harvest elements for reuse, were a key tool to gain experience and insights into deconstruction techniques and processes. The current report delivers an overview of what deconstruction entails. It gives best practice guidelines on the planning and implementation of deconstruction, as well as recommendations for improving the process.

While ReCreate’s country-specific deconstruction pilots themselves are described in a dedicated report (Vullings et al. 2024), they are also briefly summarised in the beginning of this report. The focus of the current report is, nevertheless, on turning the learnings from deconstruction pilots into generalisable guidelines that can be capitalised beyond the ReCreate project and the parties involved.

Deconstruction entails four main phases: pre-planning, structural deconstruction planning, deconstruction work planning, and finally, implementing the deconstruction. This report instructs on the different types of plans involved in each stage as well as their authors and contents.

Pre-planning involves pre-deconstruction auditing, i.e. inventorying reusable elements and gathering relevant information into an ‘inventory’ Building Information Model (BIM). The pre-deconstruction audit has been covered by another ReCreate deliverable (Vullings et al. 2022), which was delivered before ReCreate’s deconstruction pilots were fully complete. Therefore, the current deliverable briefly recaps the essentials of a BIM-based pre-deconstruction audit, and supplements and consolidates the findings of the previous report.

Authored by a qualified structural engineer, a structural deconstruction plan sets the foundations for a safe and efficient deconstruction process. It defines the deconstruction sequence based on structural stability; determines the need for temporary support and bracing measures; establishes cutting spots for connectors; gives a labelling scheme for logistics; instructs on correct lifting and transport of elements, as well as how to monitor the quality of elements on-site; and can help to define requirements for stripping.

A deconstruction work plan, devised by experts of the deconstruction company, translates the structural deconstruction plan into work processes: both the overall deconstruction process as well as element type specific processes. It covers aspects like workforce, equipment, work safety, site planning, and scheduling.

Finally, learnings acquired by implementing ReCreate’s deconstruction pilots are elaborated on. Findings are reported on deconstructing different types of elements; avoidable mistakes that were made which may influence the reusability (or at least the effort and cost of reuse) of the salvaged elements; the types of damage that is not easily preventable but an inherent part of deconstruction; and the influence of weather conditions on the deconstruction work. Additionally, special types of deconstruction projects are briefly discussed, such as partial deconstruction in the context of building remodelling, as well as combining deconstruction with conventional demolition.

While smaller, sub-process specific insights are scattered through the report, the main learnings of the key topics are distilled into checklists, given at the end of this report. The experience of the ReCreate deconstruction pilots shows that prerequisites for more widespread deconstruction already exist in that appropriately skilled workforce and suitable tools and equipment are widely available. The main technical and processual challenge in deconstruction is reconfiguring the existing know-how into safe and efficient deconstruction processes. This development can be further supported by small adjustments to existing tools that can help make the equipment even better suitable for deconstruction purposes. Nevertheless, it should be noted that a full evaluation of the success of ReCreate’s deconstruction pilots can only be made once the salvaged elements have been reused in new buildings.

3D Concrete Printing (3DCP) represents a paradigm shift in the methods for concrete construction, offering labour automation, reduced material usage and waste, and extended design flexibility. 3DCP also enforces an inherent digitalisation, facilitating interaction among various stakeholders. This requires integrating the printed elements into the digitalised workflows that support the logistics of the process. This research project examines the potential of incorporating Near Field Communication (NFC) tags into 3DCP elements to facilitate their integration into digital workflows. NFC is a subset of RFID technology designed for short-range (< 100 mm) secure data exchange.

Extrusion-based 3D concrete printing (3DCP) is a promising technique for fabricating complex concrete elements without formwork, offering advantages like cost reduction and enhanced design flexibility by decoupling manufacturing costs from part complexity. However, this extended formal freedom is still constrained by the fabrication process and material properties. This paper presents a novel method for applying topology optimisation internally i.e. preserving the external boundaries of the concrete element while reducing material use and weight. This method adapts the extrusion thickness along the part according to the expected stresses, reducing the material use while enhancing structural performance. To validate this method, three different unreinforced 3DCP beams are tested in three-point bending. Results show that beams with optimised material distributions presented a higher strength-to-weight ratio, averaging 47% and 63% compared with the conventional 3D printed beam. This paper demonstrates the potential of internal topology optimisation for improving the efficiency and sustainability of 3DCP.

3D-betongutskrift (3DCP) har uppstått som en innovativ teknik som syftartill att minska miljöpåverkan genom att eliminera behovet av formarbeteoch möjliggöra placering av material endast där det behövs. Dennaartikel analyserar hållbarheten hos 3D-betongutskrift och presenteraren studie där tre oarmerade betongbalkar testades, varav två medoptimerad materialdistribution genom att integrera topologioptimeringoch anpassa utskriftsbanor för att följa materialets interna krafter.Det resulterade i en förbättring av styrka-till-vikt-förhållandet på upptill 63 % jämfört med en traditionell balk.

The transition from conventional cast concrete to 3D Concrete Printing (3DCP) marks a paradigm shift by directly depositing fresh concrete layer upon layer according to a digital model without the need for a formwork. This technology offers the possibility of achieving innovative and complex geometries in an automated process. Additionally, the implicit digitalisation introduced by this technology streamlines the interaction among different stakeholders, thereby reducing human errors and augmenting construction quality.

Nevertheless, despite its potential, methods for fully exploiting the design capabilities of 3DCP are still largely underdeveloped. This is primarily due to the assumed separation between the design process and the generation of manufacturing instructions. While the current driver for this technology is linked to increasing productivity and reducing labour costs, its most significant contribution may well be in the manufacturing of material-efficient structures by automatically integrating structural analysis into the designprocess.

This licentiate thesis aims to extend the design scope for this rapidly maturing technology by investigating its design possibilities, relevant printing parameters, and structural optimisation capabilities within the inherent restrictions of the process. The research focuses on the development of integrated design-to-manufacture workflows for the manipulation, analysis, and optimisation of print paths considering material and process constraints. Additionally, a comprehensive literature review is conducted, with a particular emphasis on the expansive design capabilities of 3DCP.

Experimental studies encompassed the design, manufacturing, and testing of concrete prototypes using a custom-made 3DCP system based on a robotic arm. The results demonstrated that customised material distributions can be successfully programmed and executed, resulting in prototypes with enhanced structural performance. Laboratory tests on topology-optimised unreinforced 3DCP beams revealed a substantial increase in load-bearing capacity per unit weight compared to conventional 3D printing patterns. The thesis aligns with the broader sustainability goals of the construction industry. Even though the cement content in 3D printed concrete currently tends to be higher compared to conventional methods, the potential of the technology for optimising material use, minimising waste, and incorporating additional functionalities to structures presents significant opportunitiesfor reducing the environmental footprint of concrete construction. By integrating manufacturing constraints into the design process, this study delineates a pathway for extending the design possibilities of 3DCP toward the implementation of material-efficient structures with graded properties. Ultimately, this study contributes to bridging the gap between digital design and digital fabrication methods, thereby advancing concrete construction practices.

Övergången från traditionell gjuten betong till 3D-betongutskrift 3D Concrete} Printing eller 3DCP) markerar ett paradigmskifte genom att direkt deponera färsk betong lager för lager enligt en digital modell, utan behov av formar.  Denna teknik erbjuder möjligheter att uppnå innovativa och komplexa geometrier genom en automatiserad process. Dessutom förenklar digitaliseringen interaktionen mellan olika intressenter, vilket minskar mänskliga fel och ökar byggkvaliteten.

Denna licentiatavhandling syftar till att utvidga designomfånget för denna snabbt växande teknik genom att undersöka dess designmöjligheter, relevanta utskriftsparametrar och kapaciteter för strukturell optimering inom de rådande begränsningarna av processen. Forskningen fokuserar på utvecklingen av integrerade design-till-tillverkning-flöden för styrning, analys och optimering av utskriftsvägar med hänsyn till material- och processbegränsningar. Dessutom genomförs en omfattande litteraturöversikt med särskild betoning på 3DCP:s expansiva designkapacitet.

Experimentella studier omfattade design, tillverkning och testning av betongprototyper med ett skräddarsytt 3DCP-system baserat på en robotarm. Resultaten visade att anpassade materialfördelningar framgångsrikt kan programmeras och genomföras, vilket resulterade i prototyper med förbättrad strukturell prestanda. Laboratorietester på topologioptimerade oarmerade 3DCP-balkar visade en betydande ökning av bärförmåga per enhetsvikt jämfört med konventionella 3D-utskriftsmönster.

Forskningen ligger i linje med byggbranschens övergripande hållbarhetsmål. Även om cementinnehållet i 3D-utskriven betong för närvarande tenderar att vara högre jämfört med konventionella metoder, erbjuder teknologin potential att optimera materialanvändning, minimera spill och lägga till funktionaliteter i konstruktioner, vilket ger möjligheter att minska betongkonstruktioners miljöavtryck. Genom att integrera tillverkningsbegränsningar i designprocessen skisserar denna studie en väg för att utöka designmöjligheterna för 3DCP mot implementering av material-effektiva konstruktioner med varierande egenskaper. Slutligen bidrar denna studie till att överbrygga klyftan mellan digital design och digitala tillverkningsmetoder, och därmed främja betongbyggandets metoder.

Tracking of building components can be instrumental in reuse for a Circular Economy. Tracking technologies (TT) for building components can be used to identify and access information for decision-making from deconstruction to design for reuse. Prior research has mainly been concerned with single technologies, limited life cycle applicability and new construction. This study aims to explore the potential of combining multiple technologies, such as QR codes, NFC, and Bluetooth tags, with BIM to support reuse along the life cycles of prefabricated concrete components. The benefits and limitations of choices in TT are examined concerning information integration in circular construction.

In recent years, there has been a growing interest in adopting circular approaches in the built environment, specifically reusing existing buildings or their components in new projects. To achieve this, drawings, laser scanning, photogrammetry and other techniques are used to capture data on buildings and their materials. Although previous studies have explored scan-to-BIM workflows, automation of 2D drawings to 3D models, and machine learning for identifying building components and materials, a significant gap remains in refining this data into the right level of information required for digital twins, to share information and for digital collaboration in designing for reuse. To address this gap, this paper proposes digital guidelines for reusing precast concrete based on the level of information need (LOIN) standard EN 17412-1:2020 and examines several CAD and BIM modelling strategies. These guidelines can be used to prepare digital templates that become digital twins of existing elements, develop information requirements for use cases, and facilitate data integration and sharing for a circular built environment.

While 3D concrete printing (3DCP) has surged in popularity, methods to harness its design potential remain largely underdeveloped. Existing design-to-manufacture workflows most commonly restrict the design to the overall geometry and a set of print parameters that may fall outside of the scope of the designer. This study presents a novel approach to integrate design and manufacturing by an integrated design-to-manufacture workflow that allows the gradation of the wall thickness along the printed part, which can be independently manipulated using established computer graphic techniques like texture projection and mesh coloring. The effectiveness of this workflow is demonstrated through the fabrication of a test body featuring a customized surface pattern. This approach aims to extend the design scope for 3DCP, enabling the addition and editing of surface patterns without geometry or code manipulation.