Effect of Transverse and Longitudinal Confinement on the Inter-Layer Bond in 3D Printed Concrete at Elevated Temperatures (2020-12)¶

In the last decade, the study of three-dimensional concrete printing (3DCP) has become extremely popular, with a number of researchers studying the behaviour of 3DCP at ambient conditions. The interest in 3DCP has been aroused by its ability to facilitate the realization of geometrically complex objects at reduced construction time, and potentially cost, compared to conventional construction techniques. However, it is crucial to understand the effects of this new layer-wise construction technique on the fire performance of 3DPC elements, especially since negligible research is available on the behaviour of 3DPC samples in fire. In 2019 one of the first experimental studies of 3DCP at elevated temperatures was conducted by the authors, which highlighted a new failure mechanism, i.e. self-equilibrating stresses causing tension exceeding the interfacial bond strength, as opposed to dominating spalling failure in cast concrete. It is with the above mentioned in mind that the paper seeks to investigate the effect of boundary conditions on the interlayer bond behaviour of 3DPC at elevated temperatures. Six 3DPC samples were tested by exposing the samples to an incident heat flux via radiant panels, along with an additional 5 samples to obtain ambient strength properties. The temperatures were measured at various positions within the 3DPC samples. It was found that restraining the samples from movement perpendicular to the interlayer direction, can reduce the tendency of the samples to delaminate and as a result increase the post-fire flexural capacity.