The Effects of Nozzle Diameter and Length on the Resulting Strand Properties for Shotcrete 3D Printing

Abstract

Additive Manufacturing in Construction (AMC) enables new design methods and strategies within the construction industry. In particular, Shotcrete 3D Printing (SC3DP) offers a high degree of design freedom by enabling the deposition of concrete at variable layer orientation based on a wet-mix shotcrete process. However, the mechanical properties and geometry of the printed layers are dependent on the material and process parameters used. In this context, the effects of air and concrete flow rates, path planning parameters, and material parameters have been investigated in previous research. The here presented study investigates the influence of the nozzle geometry on the resulting strand properties, e.g. strand geometry, layer bond strength, and compressive strength, to evaluate nozzle diameter and length as control parameters for the SC3DP process. Experimental investigations were performed with fixed nozzle diameters between 10 and 30 mm and nozzle lengths ranging from 100 to 200 mm. The results show a significant influence of the nozzle diameter on the resulting strand geometry as well as the mechanical properties. Finally, concepts for a nozzle with a controllable outlet diameter were developed and evaluated.

Shotcrete 3D Printing ‐ Interaction of nozzle geometry, homogeneity and hardened concrete properties

“…3 point bending tests are performed with a centrally located interface according to DIN EN 196-1 [23], see Figure 5b. The raw data of the results for flexural strength were originally published in [19] and are presented here in a reproduced form.…”

“…To increase the controllability of the SC3DP process, David et al [19] investigated the possibility to influence the layer geometry by changing the nozzle outlet diameter. A strong influence of the outlet diameter on the resulting layer geometry was observed.…”

“…While small nozzle outlet diameters resulted in flat and wide samples, large nozzle outlet diameters resulted in narrow and high samples. Furthermore, a prototype of an automated nozzle has been developed that can change the nozzle diameter in parallel with the process, thus allowing the layer geometry to be changed during printing [19]. However, it was observed that in addition to an effect on layer geometry, the outlet diameter also affected the mechanical strength of the printed specimens.…”