Effect of Hydration Process on the Inter-Layer Bond Tensile Mechanical Properties of Ultra-High-Performance Concrete for 3D Printing (2024-10)¶

It is crucial to reveal interlayer interface characteristics for fully analysing the mechanical properties of 3D printed ultra-high performance concrete (3DP-UHPC). Despite its significance, the interlayer bonding behaviour of 3DP-UHPC has not been fully explored. To fill this gap, this study adopted different curing times and conditions to investigate the effect of hydration process on the interlayer microstructure and mechanical properties under different interlayer interval times. As the result show that, the interlayer microstructure remained dense for interval times less than 5 minutes, but interlayer gaps became increasingly apparent as the interval time exceeded this threshold. Promoting hydration, however, helped heal interlayer defects in 3DP-UHPC. Additionally, the interlayer bond tensile strength gradually decreased with increasing interval time but remained almost unchanged when the interval time exceeded 1 day. Notably, hot water bath curing enhanced the bond tensile strength of specimens with interval times within 60 minutes, but its improvement was insignificant for interval times exceeding 1 day. Based on these experimental results, a preliminary interlayer bond tensile stress-strain equation of 3DP-UHPC was derived. The findings of this study offer promising avenues for the improvement and promotion of 3DP-UHPC technology.