Interlayer Strength of 3D-Printed Mortar Reinforced by Postinstalled Reinforcement

Abstract

This work was designed to evaluate the interlayer strength of 3D-printed mortar with postinstalled interlayer reinforcement. Two methods of postinstalled interlayer reinforcement were considered according to the amount of overlapping. The first method did not include overlapping of the interlayer reinforcement, while the second method included overlap lengths of 20 and 40 mm. Additionally, two different curing conditions were considered: air-curing conditions and water-curing conditions. The compressive, splitting tensile, and flexural tensile strengths of 3D-printed mortar specimens with different reinforcement methods and curing conditions were investigated under three loading directions. The three loading directions were defined based on the three planes of the printed specimens. The compressive, splitting tensile, and flexural tensile strengths were dependent on the loading directions. In particular, the splitting and flexural tensile strengths decreased considerably when tensile stresses acted on the interlayers of the 3D-printed mortar specimens. However, when longitudinal interlayer reinforcement penetrated the printed layers, the flexural tensile strength or interlayer bonding strength of the printed specimens increased significantly at the interlayers. In addition, mortar specimens reinforced with overlap lengths of 20 and 40 mm were investigated in this study. The flexural tensile strength or interlayer bonding strength of 3D-printed mortar decreased after treatment under air-curing conditions because the interlayers of the printed mortar formed more pores under these conditions and were more vulnerable under loading. Finally, the findings of this study suggested that interlayer reinforcement is a potential method for improving the interlayer bonding strength of 3D-printed mortar.

Automated Reinforcement during Large-Scale Additive Manufacturing: Structural Assessment of a Dual Approach

“…As such, in the present study, 150 mm was considered as the maximum length of penetration. Park et al used two different lapping lengths of 20 mm and 40 mm, which is approximately 6 and 13 times of rebar diameter (3 mm), respectively, for 100-300 mm length reinforcement [36]. These studies show that different lapping lengths could be required based on reinforcement characteristics.…”

“…Park et al studied interlayer reinforcement inserted in 3D-printed specimens with and without overlapping. Anisotropic properties were observed in all specimens, indicating further research is needed to understand the effects of overlapping [36]. Marchment and Sanjayan investigated center-and off-center-lapping for lengths of 20, 17, 14, and 11 times the bar diameter (7 mm diameter deformed steel bar) and found that a minimum lap of 20 times diameter was necessary for the 3D-printed specimen to achieve a flexural strength comparable to that of a single rebar [35].…”

A Feasibility Study on the Lateral Behavior of a 3D-Printed Column for Application in a Wind Turbine Tower

“…Hass and Bos [19] presented a novel reinforcement method utilizing screw-type reinforcements, which showed improved interlayer bonding strength in printed concrete according to the failure patterns observed in 3-point bending and pullout tests. Park et al [20] investigated the effect of the overlap length of screwed interlayer reinforcement on the bonding strength of 3D concrete. It was reported that the longer overlap length of the interlayer reinforcement significantly improved the postcracking behavior of 3D-printed concrete.…”