Direct printing test for buildability of 3D-printable concrete considering economic viability

Buildability, i.e. the ability of a deposited material bulk to retain its dimensions under increasing load, is an inherent prerequisite for formwork-free digital concrete construction (DC). Since DC processes are relatively new, no standard methods of characterization are available yet. The paper presents direct printing test as a practice-oriented approach, in which buildability test parameters are determined by taking various process aspects and construction costs into consideration. In doing so, direct links between laboratory buildability tests and target applications are established. A systematic basis for calculating the time interval (TI) to be followed during laboratory testing is proposed for the full-width printing (FWP) and filament printing (FP) processes. The proposed approach is verified by applying it to a high-strength, printable, fine-grained concrete. Comparative analyses of FWP and FP revealed that to test the buildability of a material for FP processes, higher velocities of the printhead should be established for laboratory tests in comparison to those needed for FWP process, providing for equal construction rates.