Figure 6. Summary of the flexural strength results
Because of the compilation, it can be stated that all sample batches produced with the new tool can generate high flexural strengths with little deviation. Similar to the pressure tests, the sprayed samples also showed the highest strength.
To assess the bond between the sprayed layer and the extruded layer, the area was subjected to a tensile test. The mean value is 2 MPa (Min. 1.9 MPa Max. 2.2 MPa). The fracture took place in the extrudate. According to DIN 18555-6 it is a cohesive fracture. This means that the contact zone is more resilient than the joining partners are.
Overall, it can be stated that the extrudates produced with the new tool achieve a very high level in terms of strength and deviations.
4. Conclusions
The aim of the work was to determine and compare the material properties of test specimens produced by casting (in accordance with standards) and by means of extrusion technology to be able to draw conclusions about anisotropic material behaviour caused by the extrusion process. As a part of the investigation, process-related influences on the mechanical parameters of additively manufactured concrete elements were examined and evaluated in more details. Based on the findings obtained, design and dimensioning of components can be conducted and thus guidelines for components can be achieved. With the guidelines derived from this, material utilization and economic efficiency can be improved and the principles of lightweight construction can be implemented.
Acknowledgements
The European Regional Development Fund (ERDF) via the Saxon Development Bank (SAB) funded the extrusion system used for this article. A priority program SPP 2187 of the DFG funded the development of the tool and the research performance. The authors would like to thank the donor of subsidies for the financial support.
References
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[12] DIN EN 12390-3: Prüfung von Festbeton - Teil 3: Druckfestigkeit von Probekörpern. 2009 .
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[14] DIN 18555-6: Prüfung von Mörteln mit mineralischen Bindemitteln; Festmörtel; Bestimmung der Haftzugfestigkeit .1987 .
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