3D printing concrete (3DPC) is a fairly new technology that is being developed in many countries around the world. The aim is to (i) increase the productivity on site, (ii) improve the quality by reducing the number of errors due to the human factor and (iii) make more advanced member shapes possible. The 3DPC technology is most competitive for making slender and thin structural members. In cases where massive concrete members are needed, 3DPC will have difficulties to compete with cast concrete, e.g., self-compacting concrete (SCC). In many cases, the combination of 3DPC and SCC might be the best solution. One example is columns where the 3DPC constitutes the (permanent or lost) formwork that in a second step is filled with SCC. In an ongoing research project at KTH, composite concrete columns of this type are investigated through a literature survey and laboratory tests. The literature is scarce but promising. Two B.Sc. projects were conducted during spring and autumn 2021. 3DCP forms of a maximum height of 2,4 m were able to withstand the form pressure from SCC without cracking, leakage or any other damage. Bond strength measurements on one of the composite columns showed values between 0,3 and 1,4 MPa, i.e., in the same range as frequent values in the field. This project constitutes the platform for further tests where higher composite columns will be subjected to load-carrying capacity tests as well as durability tests. If also these tests will be successful, it will be possible to save both natural resources and costs by making the 3DPC in high performance concrete and the SCC in a lower strength class with a reduced cement content.
Part of proceedings ISBN 978-294064315-8
QC 20221109