Title:
How Support Materials Can Reduce the Need for Buildability in 3D Printed Concrete Mix Design
Author(s):
Grout
Publication:
Web Session
Volume:
ws_S24_Grout.pdf
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
3/23/2024
Abstract:
A major issue complicating concrete mix designs for the purposes of concrete 3D printing is the need to meet the conflicting demands of being both low enough viscosities to maintain pumpability and the need to be inelastic enough to maintain buildability under subsequent printed layers. This research looks at how using sand as a support material during printing can reduce the demand for buildability and, therefore, reduce the need for the expensive admixtures currently needed to create the complex mix designs used in concrete 3D printing today. This is demonstrated by printing three different domes using a mix with a low buildability. The low buildability was created with an increased water-to-cement ratio of 0.35. Due to material limitation, buildability failure could not be induced through excessive water content alone. To induce failure, weights were gradually added to the top of a completed print to simulate the weight of additional layers until failure due to buildability was reached. The first dome was printed solid. Weights were added until the print collapsed under the additional weight. The weight that caused that failure was recorded. The second dome was created by using sand as a support material. At the completion of each layer, the print was paused, and sand was placed on the inside of the dome to a height level with the top of the completed layer. Once the print was completed, weights were added until the print collapsed under the additional weight and that weight was recorded. The third dome was printed inside retaining walls. At the completion of each layer the print was paused, and sand was placed inside the dome to a height flush with the top of the completed layer. The space between the print and retaining wall was also filled with sand.