Abstract
The creation of concrete shells from customized prefabricated modules is a novel approach that facilitates the construction of free-form surfaces considerably. In the framework of the Adaptive Concrete Diamond Construction (ACDC) project at TU Dresden, a material for 3D printing of the outer contours of such modules has been developed based on the principles of Strain Hardening Cementitious Composite (SHCC). In addition to its high ductility, the required material must also be suitable for 3D printing while enabling the achievement of high geometric accuracy in the manufacture of the modules. To gain the required performance, cellulose ether and starch ether were used specifically to extend the open time, for a longer period of maintaining initial workability, as well as for enhancing shape stability and surface quality. An extensive experimental program was carried out to evaluate the outcomes of the material modifications, including flow table tests, water retention tests, and several specific tests to determine the adhesiveness of the fresh SHCC. For hardened SHCC, surface roughness was assessed using a laser 3D scanner in addition to testing its mechanical properties.
Highlights
Concrete shells have been known at least since the construction of the Roman Pantheon in the 2nd century AD
To achieve better conformity between the tested material and the material subjected to extrusion in the 3D printing process, the Strain Hardening Cementitious Composite (SHCC) was remixed for 30 s every 10 min and immediately prior to testing
Where Ws is the mass of water retained by the substrate and WSHCC is the mass of water in the sample of SHCC placed in the ring
Summary
Concrete shells have been known at least since the construction of the Roman Pantheon in the 2nd century AD. The necessary measures include a considerable reduction in the use of building materials, which, in sum, currently account for about 11% of all CO2 emissions [4] Against this background, concrete shells, the construction of which requires relatively small amounts of material, may experience a new dawn. Smooth contact surfaces can be achieved by means of post-processing, the authors’ effort is to avoid methods such as robotic milling or grinding to keep the production chain as efficient and timesaving as possible Helpful in this context is that it is planned to place elastic rubber gaskets between the modules during assembly.
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