Control of Strand Properties Produced with Shotcrete 3D Printing by Accelerator Dosage and Process Parameters

Shotcrete 3D Printing (SC3DP) has recently evolved as a large-scale additive manufacturing technique. The major advantage of this technique is the high manufacturing speed for creating large-sized monolithic structures. However, to control this technique properly, the combined effects of process parameters and rheological properties of the concrete need to be fully understood. Therefore, the effect of accelerator dosage (0%, 2%, 4%, 6%) on the material’s yield stress is quantified with a penetrometer up to 90 min after deposition. The vertical deformation of strands is also found to correlate with yield stress. Moreover, the resulting geometry of the strands is analyzed. Here, an increase in strand height and a decrease in strand width is determined with increasing accelerator dosage. Among other factors, this is deduced to the opening angle when material leaves the nozzle. To compensate unwanted changes in geometry due to accelerator, process parameters to modify the geometry are studied as well. Therefore, the effect of traverse speed, nozzle-to-strand-distance and volume air flow on the geometry is quantified. Finally, the possibilities to use the findings of the effect of accelerator dosage and process parameters during printing process purposefully are discussed.