A Direction-Independent Reinforcement by Combination of Fiber Reinforced Cementitious Composite and Automated Pin Insertion

In recent years, 3D concrete printing (3DCP) systems have attracted great attention in the construction field and is in fierce development competition. 3DCP systems cause discontinuities between layers and results in mechanical performance degradation of the laminated structures. Therefore, numerous reinforcement methods have been proposed, however, many of proposals include problems such as limited effective reinforcement directions and the necessity of combining conventional labor-intensive construction site work. In this study, we proposed a novel reinforcement mechanism which the combines fiber-reinforced cementitious composites (FRCC), for reinforcing the horizontal direction, and an automated insertion mechanism of reinforcement steel pins, penetrating between layers for the vertical direction. FRCC layers with reinforcing pins inserted by the automated insertion system were prepared to realize this proposal. A bending test was conducted on the obtained specimens by cutting from the laminates. The results showed the direction-independent reinforcing effect of both parallel and vertical to the printing direction. In the horizontal direction, strength and toughness were increased due to the FRCC characteristics, and in the strength in vertical direction, in which the FRCC effect was limited according to previous studies, was increased up to approximately 50% by the inserted reinforcing pins between layers.