Additive Manufacturing of Steel-Reinforced Concrete by Combination of Selective Paste Intrusion and Wire Arc Additive Manufacturing: Impact of Heat Generated by WAAM on Bond Behavior of the Reinforcement

Integrating Wire Arc Additive Manufacturing (WAAM) into the Selective Paste Intrusion (SPI) process represents a groundbreaking approach for fabricating reinforced concrete structures with complex geometries. This study investigates the bond strength between concrete and WAAM reinforcement under varying temperature conditions to understand the behavior of heated reinforcement bars within fresh concrete and its effect on the related bond strength. By conducting pull-out tests according to RILEM RC6, WAAM reinforcement bars were heated to predefined temperatures of 20 °C (ambient), 60 °C, 80 °C, and 200 °C for 18 min. The results show that while moderate thermal exposure (60 °C and 80 °C) led to a slight reduction in the maximum bond strength, a notable degradation occurred at 200 °C, indicated by a marked decrease in both maximum bond stress and early bond development. These findings provide initial insights into the thermal limitations of WAAM integration within SPI processes. The goal is to address the challenges associated with integrating WAAM into SPI, particularly the adverse effects of high temperatures generated during the welding process on the rheological properties of the cement paste, the penetration behavior of the paste in the particle bed, and ultimately, the mechanical properties of the hardened concrete. This technique allows for producing nearly free-formed reinforcements, thus complementing the advantage of SPI in producing free-formed structures of almost any geometry.