Custom-fit components, optimized vehicle parts or weight-reduced aircraft components - 3D printing technology is already being used in many different industries. With additive manufacturing, or better known as 3D printing, components are produced by applying the material in layers. The technology allows the geometrical shape and structure of the components to be formed as required. In architecture, functions such as thermal insulation or light transmission can be directly implemented in façade components. Efficient production reduces energy and material consumption. Each component can be designed individually.
In a project called "LC3D" (Lightweight Concrete 3D Printing), researchers at the Technical University of Munich have investigated the possibilities of additive processes with optimized lightweight concrete formulations. Dennert Poraver GmbH, manufacturer of the mineral lightweight aggregate expanded glass granulate, is an important industrial partner in the project and supplies expanded glass granulate in various grain sizes as a raw material for the production and optimisation of printable lightweight concrete. The objective was to develop a concrete formulation with low bulk density, good thermal insulation properties, sufficient compressive strength and suitable stability.
The researchers at TUM have designed and built an extrusion plant for processing the special lightweight concrete. The concrete mix is pumped through a nozzle and formed into strands about 1 x 2.5 centimeters thick. The nozzle itself mounted on a robot arm. This allows the material to be applied precisely to the points calculated by the computer and the desired shape can be formed.
A particular challenge was the necessary rapid setting of the concrete, which decisively determines the stability and quality of the printed elements during production. In addition, the pumpability and flow behavior had to be taken into account during the development of the recipe. Poraver® expanded glass as a lightweight aggregate in the concrete recipe supports these factors positively. Thanks to the microporous structure inside the Poraver® grain, stable and small cavities can be introduced in a controlled manner, thus improving thermal insulation. The low bulk density also results in a considerable weight saving in the mortar. This allows filigree construction elements and larger overhangs.
The results so far are already promising and could in the near future boost the use of 3D concrete printing in the construction sector as an innovative manufacturing technology. The final report is still pending and will be available shortly. In the following video you will get a very good impression of the processing and the test setup in the rooms of the TU Munich:
(Video: Technical University of Munich)
The classic construction method with concrete is by casting concrete. The liquid concrete is poured into a prefabricated formwork and cured in it. However, there are limits to the shaping of components with this process.
Besides selective binding, the extrusion process is a widely used 3D printing process. The extrusion technology developed by most research institutes is the so-called multi-layer extrusion, in which the material is placed layer by layer over a controllable nozzle to create the object. Well-known multilayer extrusion processes are Contour Crafting andConcrete Printing
Contour Crafting is a multi-layer extrusion process invented by Behrokh Khoshnevis at the University of Southern California. It is a pressure device mounted on a crane, which is used on site. Using the controllable nozzle, a strand of cement mortar is applied in layers of approximately 13 mm.
The CONPrint3D- technology was developed at the Technical University of Dresden, which allows monolithic cross-sections of several decimetres to be printed in a single pass. With this process, concrete with standard aggregates of up to 16 mm grain size can be used to produce solid concrete structures as a substitute for masonry.
Concrete Printing (3DCP) is also a multi-layer extrusion process for concrete mortar, invented at Loughborough University. The Concrete Printing process offers finer layer thicknesses around 4-6 mm. This allows better control of the geometry produced. The technology is being further developed at various institutions, such as TU Eindhoven.
If you have any questions about 3D concrete printing or lightweight concrete, feel free to contact us. We will be happy to support you in optimizing formulations and advise you on the various Poraver® grain sizes.