Anisotropic properties of additively manufactured lightweight concrete
elements
Marco Lindner*, Ralf Gliniorz, Henrik Funke, Sandra Gelbrich
E-mail: marco.lindner@mb.tu-chemnitz.de
Keywords: Robotic 3D printing, additive manufacturing, extrusion with
concrete, anisotropic properties,
Robotic concrete extrusion is a novel additive manufacturing process (3D
concrete printing) and is part of a continuously digitally controlled
value chain. According to the state of the art, concrete is considered
to be an isotropic material due to the manufacturing process. However,
for the additive manufacturing process, the isotropic approach hast to
be reconsidered due to the layered structure. It can be assumed that due
to the layered structure, the material properties vary depending on the
deposition direction and the geometry of the layers. The aim of the work
was to record the material-technical characteristics of extruded
elements manufactured according to standards in comparison with concrete
recipes. Process-related influences on the mechanical parameters of
additively manufactured concrete elements were examined and evaluated in
more detail. Based on the findings obtained, the dimensioning, design
and measurement of components can be carried out and thus guidelines for
components can be derived. With these derived guidelines, the material
utilization and economic efficiency can be improved.
1. Introduction
Rapidity, precision, economics and resource saving are the most
important requirements of the construction industry of the future.
Modern lightweight construction technologies can implement these
requirements and add the aspects of design freedom, efficiency, and
sustainability. Therefore, the development of new manufacturing
technologies for highly stressable, durable and free-forming
prefabricated concrete components with low material and energy input is
the focus of the research group “Lightweight Constructions in Civil
Engineering” (LBW) at the Chemnitz University of Technology. In
general, the well-known building material concrete is considered
isotropic due to the material properties and classical processing
methods (casting, laminating e.g.). In contrast, the application of
additive manufacturing processes result in anisotropic material
properties because of the layered structure of the concrete elements by
means of extrusion.
The aim of the work was to determine and compare the material properties
of test specimens produced by casting (in accordance with standards DIN
EN 12390) and by means of extrusion technology to be able to draw
conclusions about anisotropic material behavior because of the extrusion
process.
In addition, numerical investigations were conducted to reproduce the
results of the mechanical tests. As a part of the investigation,
process-related influences on the mechanical parameters of additively
manufactured concrete elements were examined and evaluated in more
detail. Based on the findings obtained, design and dimensioning of
components can be conducted and thus guidelines for components can be
achieved. With these derived guidelines, material utilization and
economic efficiency can be improved and the lightweight construction
principles can be implemented.
2. Material and methods
2.1. Experimental procedure
Additive manufacturing with mineral materials, in particular
robot-assisted concrete extrusion, is a new manufacturing technology in
construction and offers architects and civil engineers a variety of
options for implementing lightweight construction concepts. At the same
time, it requires great care in selecting the correct manufacturing
parameters and material composition. The development was executed at the
research facility “LBW RoboArena” (Table 1 .) at Chemnitz
University of Technology [1, 2, 3, 4, 5, and 6].
Table 1. Research facility “LBW RoboArena” at research group
LBW