Rivet Reinforcement for Concrete Printing (2023-03)¶

This study demonstrates and experimentally evaluates a novel reinforcement strategy capable of rapidly bridging the interlayer interface in printed concrete. Modified male-female blind rivets and flexible stainless-steel wire ropes are proposed as orthogonal and longitudinal reinforcement, respectively. To investigate the proposed orthogonal reinforcement, the displacement of a rivet strand during the fastening process is analysed through digital image correlation to compare two different nosepieces attached to a riveting tool. Additionally, the compressive force exerted on a strand and the time elapsed during fastening are evaluated. Tensile forcedisplacement, elasticity and yield strength responses are presented for rivet strands and rope samples. Fourpoint flexural tests are conducted on orthogonally reinforced printed prisms and compared with unreinforced prisms. Rivet strands are rapidly realised with 0.54 mm average lateral displacement when a novel nosepiece, specifically developed in this research, is attached to the pneumatic riveting tool. Further, a rivet-to-rivet connection is made in 0.29s on average. Hardening and ductile behaviour are observed in the tensile results of rivet strands (82 MPa average fracture stress at 1.808% strain) compared to the more consistent but lesser hardening and ductility of the wire ropes (1645 MPa average fracture stress at 1.582% strain). Nevertheless, the flexural performance of the concrete prisms is significantly improved by the addition of the proposed rivet reinforcement, providing hardening behaviour as opposed to the softening behaviour exhibited by the unreinforced control group, resulting in a 230% average increase in the elastic moment capacity.