Interface Bonding Characteristics of 3d Printed Ultra-High Performance Concrete after Elevated Temperatures

Abstract

This study explored the influence of elevated-temperature exposure and interlayer time intervals on the interface bonding behaviour of hybrid fibre 3D printed ultra-high performance concrete (3DP-UHPC). Mould-casting concrete (MC-UHPC) specimens of different casting time intervals were also used as references to analyse the differences in bonding performance. The bonding strength of both 3DP-UHPC and MC-UHPC after elevated-temperature exposure was measured, and a relationship model for the bonding strength of hybrid fibre 3DP-UHPC in elevated-temperature environments was proposed. Results revealed that local damage occurred during heating up to 800°C. The addition of 0.5% polypropylene fibres delayed bursting behaviour of 3DP-UHPC during heating and enhanced its resistance to elevated temperatures by providing a pathway for moisture loss. The bonding strength decreased with longer time intervals, as well as above 400°C, the melting and volatilization of polypropylene fibres negatively affected the bonding strength of 3DP-UHPC. This study's findings offer insights for the development and design of 3DP-UHPC structures in elevated-temperature environments.

Keywords: 3DP-UHPC, hybrid fibre, elevated-temperature, interface bonding performance, bonding strip