The Assessment of the Buildability and Interlayer Adhesion Strength of 3D-Printed Mortar

Abstract

In recent years, 3D printing, also known as additive manufacturing (AM), has been gaining popularity in the field of construction. The application of 3D printing in construction has allowed for automation to reach an industry currently facing shortages in labor and natural resources, increasing costs, and increasing demand for sustainability and affordable housing in all markets. However, one of the primary challenges in upscaling current 3D printing technology in construction is the ambiguity in its testing procedures due both to the novel methods of applications and unique material properties. To date, only a few official testing standards for 3D construction printing are available (i.e., ICC-ES AC509, UL 3401). These standards, however, are still at their early stages and have yet widely adopted. This study focuses on the assessment of the material properties at both fresh (plastic) and hardened stages of a commercially available 3D-printed mortar. This manuscript also presents the development of new test methods to assess the interlayer adhesion strength of 3D-printed mortar and the buildability of the material. The interlayer adhesion strength in 3D-printed mortar was assessed by testing printed specimens for tensile strength perpendicular to the printing direction. The buildability of the mortar was defined by its ability to maintain its shape and integrity during the printing process without completely collapsing or showing signs of significant deformation. For this purpose, a buildability test was developed by printing and recording the maximum achievable printing height of a specific structure under specific printing parameters, such as the shape and dimension of the structure and filament, printing speed, extrusion rate, water level, and printing environment. These printing parameters were specifically defined and controlled to maintain the consistency and repeatability of the test. The buildability test results indicate that a faster vertical building rate leads to a lower maximum height for the given material and vice versa.