Enclosing Reinforcement Structures in Shotcrete 3D Printing

The Effect of Reinforcement Geometry and Accelerator Dosage on the Formation of the Bond Area





Additive Manufacturing in Construction, Concrete Printing, Shotcrete 3D Printing, Protruding Rebars, Accelerator, Void Formation, Bond Quality


Integrating reinforcement into existing concrete 3D printing processes represents one of the key challenges in further automating the additive manufacturing of structural concrete components. A number of different approaches are currently being investigated. In this context, the integration of prefabricated reinforcement structures as well as the process-parallel assembly of reinforcement, e.g. by additive metal arc welding or joining of short rebars, are potential strategies. A common feature of both of these reinforcement strategies is that rebars protrude from the concrete surface in variable orientations during the printing process and need to be enclosed in concrete. Due to the spray application, Shotcrete 3D Printing (SC3DP) offers a good basis for realizing such reinforcement enclosures without the use of specially adapted nozzles. However, it is essential to systematically analyze material properties, e.g. accelerator dosage, and process properties, e.g. reinforcement orientation, in order to define limits for the application. For this reason, the present study investigates the influence of accelerator dosage (0 - 4 %) and reinforcement geometry (spacing, inclination, crossings) on the formation of voids. It is observed that with increasing accelerator dosage, the reinforcement structure increasingly acts as a blocking element for material spreading. The adhesion of the concrete to the reinforcement during spraying creates a shielding effect that increasingly leads to void formation. Finally, the potential and limitations of using prefabricated reinforcement structures in SC3DP are discussed.


Download data is not yet available.


Buswell, R.A.; Bos, F.P.; Da Silva, W.R.L.; Hack, N.; Kloft, H.; Lowke, D.; Freund, N.; Fromm, A.; Dini, E.; Wangler, T.; et al. Digital Fabrication with Cement-Based Materials: Process Classification and Case Studies. In Digital Fabrication with Cement-Based Materials; Roussel, N., Lowke, D., Eds.: Springer International Publishing: Cham, 2022, pp. 11–48, https://doi.org/10.1007/978-3-030-90535-4_2. DOI: https://doi.org/10.1007/978-3-030-90535-4_2

Bos, F.P.; Menna, C.; Pradena, M.; Kreiger, E.; da Silva, W.L.; Rehman, A.U.; Weger, D.; Wolfs, R.; Zhang, Y.; Ferrara, L.; et al. The realities of additively manufactured concrete structures in practice. Cement and Concrete Research 2022, 156, 106746, https://doi.org/10.1016/j.cemconres.2022.106746. DOI: https://doi.org/10.1016/j.cemconres.2022.106746

Kloft, H.; Empelmann, M.; Hack, N.; Herrmann, E.; Lowke, D. Reinforcement strategies for 3D‐concrete‐printing. Civil Engineering Design 2020, 2, 131–139, https://doi.org/10.1002/cend.202000022. DOI: https://doi.org/10.1002/cend.202000022

Mechtcherine, V.; Buswell, R.; Kloft, H.; Bos, F.P.; Hack, N.; Wolfs, R.; Sanjayan, J.; Nematollahi, B.; Ivaniuk, E.; Neef, T. Integrating reinforcement in digital fabrication with concrete: A review and classification framework. Cement and Concrete Composites 2021, 119, 103964, https://doi.org/10.1016/j.cemconcomp.2021.103964. DOI: https://doi.org/10.1016/j.cemconcomp.2021.103964

Freund, N.; Lowke, D. Interlayer Reinforcement in Shotcrete-3D-Printing. Open Conf Proc 2022, 1, 83–95, https://doi.org/10.52825/ocp.v1i.72. DOI: https://doi.org/10.52825/ocp.v1i.72

Freund, N.; Dressler, I.; Lowke, D. Studying the Bond Properties of Vertical Integrated Short Reinforcement in the Shotcrete 3D Printing Process. In Second RILEM International Conference on Concrete and Digital Fabrication; Bos, F.P., Lucas, S.S., Wolfs, R.J., Salet, T.A., Eds.: Springer International Publishing: Cham, 2020, pp. 612–621, https://doi.org/10.1007/978-3-030-49916-7_62. DOI: https://doi.org/10.1007/978-3-030-49916-7_62

Kloft, H.; Empelmann, M.; Oettel, V.; Ledderose, L. 3D Concrete Printing – Production of first 3D Printed Concrete Columns and Reinforced Concrete Columns. BFT International, no. 6 2020, 28–37.

Dörrie, R.; Laghi, V.; Arrè, L.; Kienbaum, G.; Babovic, N.; Hack, N.; Kloft, H. Combined Additive Manufacturing Techniques for Adaptive Coastline Protection Structures. Buildings 2022, 12, 1806, https://doi.org/10.3390/buildings12111806. DOI: https://doi.org/10.3390/buildings12111806

DIN EN 1992-1-1:2011-01, Eurocode_2: Bemessung und Konstruktion von Stahlbeton- und Spannbetontragwerken_- Teil_1-1: Allgemeine Bemessungsregeln und Regeln für den Hochbau; Deutsche Fassung EN_1992-1-1:2004_+ AC:2010; Beuth Verlag GmbH: Berlin, https://dx.doi.org/10.31030/1723945. DOI: https://doi.org/10.31030/1723945

Kloft, H.; Krauss, H.-W.; Hack, N.; Herrmann, E.; Neudecker, S.; Varady, P.A.; Lowke, D. Influence of process parameters on the interlayer bond strength of concrete elements additive manufactured by Shotcrete 3D Printing (SC3DP). Cement and Concrete Research 2020, 134, 106078, https://doi.org/10.1016/j.cemconres.2020.106078.Dreßler, I.; Freund, N.; Lowke, D. The Effect of Accelerator Dosage on Fresh Concrete Properties and on Interlayer Strength in Shotcrete 3D Printing. Materials Journal, Special Issue “Concrete 3D Printing and Digitally-Aided Fabrication” 2020, https://doi.org/10.3390/ma13020374. DOI: https://doi.org/10.1016/j.cemconres.2020.106078

DIN EN 14488-2:2006-09, Prüfung von Spritzbeton_- Teil_2: Druckfestigkeit von jungem Spritzbeton; Deutsche Fassung EN_14488-2:2006; Beuth Verlag GmbH: Berlin, https://dx.doi.org/10.31030/9710986. DOI: https://doi.org/10.31030/9710986

Lootens, D.; Jousset, P.; Martinie, L.; Roussel, N.; Flatt, R.J. Yield stress during setting of cement pastes from penetration tests. Cement and Concrete Research 2009, 39, 401–408, https://doi.org/10.1016/j.cemconres.2009.01.012. DOI: https://doi.org/10.1016/j.cemconres.2009.01.012

Hack, N.; Kloft, H. Shotcrete 3D Printing Technology for the Fabrication of Slender Fully Reinforced Freeform Concrete Elements with High Surface Quality: A Real-Scale Demonstrator. In Second RILEM International Conference on Concrete and Digital Fabrication; Bos, F.P., Lucas, S.S., Wolfs, R.J., Salet, T.A., Eds.: Springer International Publishing: Cham, 2020, pp. 1128–1137, https://doi.org/10.1007/978-3-030-49916-7_107. DOI: https://doi.org/10.1007/978-3-030-49916-7_107

Maboudi, M.; Gerke, M.; Hack, N.; Brohmann, L.; Schwerdtner, P.; Placzek, G. Current Surveying Methods for the Integration of Additive Manufacturing in the Construction Process. In The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLIII-B4-2020, 2020 https://doi.org/10.5194/isprs-archives-XLIII-B4-2020-763-2020. DOI: https://doi.org/10.5194/isprs-archives-XLIII-B4-2020-763-2020

Lachmayer, L.; Dörrie, R.; Kloft, H.; Raatz, A. Process Control for Additive Manufacturing of Concrete Components. In Third RILEM International Conference on Concrete and Digital Fabrication; Buswell, R., Blanco, A., Cavalaro, S., Kinnell, P., Eds.: Springer International Publishing: Cham, 2022, pp. 351–356, https://doi.org/10.1007/978-3-031-06116-5_52. DOI: https://doi.org/10.1007/978-3-031-06116-5_52



How to Cite

Freund, N., Dörrie, R., David, M., Kloft, H., Dröder, K., & Lowke, D. (2023). Enclosing Reinforcement Structures in Shotcrete 3D Printing: The Effect of Reinforcement Geometry and Accelerator Dosage on the Formation of the Bond Area. Open Conference Proceedings, 3. https://doi.org/10.52825/ocp.v3i.227

Conference Proceedings Volume


Contributions to the symposium "Visions and Strategies for Reinforcing Additively Manufactured Constructions 2023"
Received 2023-04-15
Accepted 2023-05-30
Published 2023-12-15