Penetration Reinforcing Method for 3D Concrete Printing

Large scale construction 3D Concrete Printing (3DcP) has gained much attention worldwide with the recent developments of many new technologies and proof of concept structures. One inherent limitation in 3DcP is the automatic laying of reinforcement. So far, the methods proposed for integrating vertical reinforcement are rudimentary and involve manual post processes. Majority of 3DcP wall structures overcome this issue by using the printed section as a shell and after hardening involve manual post processes to reinforce the structure. In this paper a new method of reinforcing is introduced termed the Layer Penetration Reinforcing Method (LPRM). This process involves the printing of a predetermined number of layers, then the subsequent penetration of pre-cut reinforcement through the fresh layers. To prove the concept a lab scale wall (300 mm tall) is printed and reinforced with 7 mm deformed steel bar and ×9 mm stainless steel helical bar. The wall is cut into 100 mm × 60 mm × 300 mm beam sections and tested in 3-point bending with the bar sitting a depth of approximately 70 mm to measure the flexural strength. The samples are compared to conventionally reinforced concrete. Results have shown that the printed beams with deformed bar and helical bar increase the flexural strength of the wall by 184% and 142% respectively. Deformed bar proved superior over helical bar in reinforcing a 3DcP section by obtaining a flexural strength 83% that of a conventional reinforced section, compared to 47% for helical bar.