CCR Digital Concrete 2020 SI (2020-06)¶

The development of digital fabrication of cement-based materials (DFC) is taking the construction industry by storm. New horizons come into view by the promises of geometrical freedom, high construction speed, lack of hard physical labour, and reduced use of primary and secondary materials. However, this comes at a price. Behind the seemingly easy free deposition of fresh material, complex phenomena and fundamental questions hide. DFC engages the material in a phase that is normally left untouched: during the transition from fluid to solid. The (partial) absence of formwork that characterizes most DFC processes, poses many fascinating new challenges, in fields ranging from material design (including reinforcement) and process modelling, to quality control and product application. The complete interaction between design, material, process, and product needs to be rethought (Fig. 1a). This is now attracting attention from research groups around the world. In the slipstream, an increasing number of conferences on the topic has been initiated as well. Two years ago, Digital Concrete 2018, hosted by the ETH Zurich, was the first dedicated conference in this field worldwide. In July of this year, the TU Eindhoven hosts Digital Concrete 2020, the 2^nd RILEM International Conference of Concrete and Digital Fabrication, online. In a mere two years, the number of papers has almost quadrupled, which illustrates the rapid expansion of the field. The Digital Concrete conferences are sponsored by the RILEM Technical Committee 276 Digital Fabrication with Cement-based materials, and are set to be continued under the umbrella of subsequent RILEM Technical Committees after the termination of TC 276, with the follow-up event expected to take place at Loughborough University in 2022. Digital Concrete 2020 is the topic of this Special Issue of Cement and Concrete Research. In a sense, it is the successor of issue 112, which was dedicated to the 2018 event. The current issue collects 13 keynote and invited papers across the scale of the conference scope: from the studies of the crucial physico-chemical phenomena, through process modelling, to mixture design, and finally applications. A bird's eye view of the field is provided by Khan et al. [1]. They present a solid historical and technological embedding of the technologies now recognized under the umbrella of DFC. Based on their broad review, featuring a particularly worthwhile section on numerical modelling, the authors conclude the future for 3D printing in construction is bright and outline a path for its further development. This paper thus provides an excellent introduction into the subject matter.