Interfaces between filaments of 3-D printed concrete structures have been shown to have lower resistance than the virgin material in mechanical action. The adhesive tensile and shearing resistance is influenced by amongst others the pass time, i.e. the duration between printing the filament layer and its substrate layer, the consistency of the material, the filament layer shape and deposition height. Recent studies have shown that the interface may dominate the response in fire, forming a debonding failure mechanism due to the thermal gradient and associated tensile stress. The debonding failure could lead to structural instability. Whereas fiber reinforcement of the 3-D printable material is possible and reported, transverse reinforcement across interfaces presents the missing link for in-plane and out-of-plane shear and flexural resistance, as well as thermo-mechanical reinforcement. This contribution presents comparative flexural responses of 3-D printed elements with and without reinforcing links, comparing the responses of reference unheated specimens with those of specimens cooled down from elevated temperatures. The concept of automated link reinforcement of a 3-D printed fiber-reinforced concrete modular load-bearing walling system is presented.
Courtesy of American Concrete Institute