Effect of vibration on rheological properties of concrete and its application in concrete 3D printing

In the last decade, 3D printing concrete has seen increasing popularity. It has the potential to increase construction efficiency and safety, as well as reduce costs. Typically, concrete that is 3D printed must achieve two targets: flow through the printer to exit the nozzle and hold its shape once printed. These two targets require the concrete to have contrasting rheological properties. This opposing requirement is typically addressed by extruding stiff cementitious material or by dosing the fluid cementitious material with chemical admixtures as it exits the nozzle to cause rapid hardening. The high extrusion pressure and/or thorough mixing at the nozzle limits the use of aggregates in printable concrete mixtures. To address the hurdles of printing aggregates, especially coarse aggregates, this study proposes and investigates the use of vibration to facilitate the rheological properties required for 3D printing. Increasing aggregate content has the potential to reduce material costs and decrease shrinkage compared to cementitious mixtures that are 3D printed currently. Vibration causes an immediate and reversible change in the rheological properties of granular suspensions such as concrete. This dissertation examines the role aggregates (granular material) play in the rheology of concrete, both without and during vibration. It was found that having more than 30 % aggregates (by volume) substantially increased the yield stress and viscosity of the mixtures compared to mixtures with less than 30 % aggregate volume. Vibrating concrete caused a reduction in yield stress by up to 76 %. The sensitivity of the rheological properties to changing the constituents of the mixture design was statistically modeled to help with mixture design for 3D printing using a central composite experimental design. The volume of paste and the water-to-cement ratio of a mixture were found to have a significant effect on the fresh and rheological properties of the mixtures. Additionally, the effect of changing vibration energy on concrete rheology was explored. It was found that the reduction in yield stress during vibration correlated well with the input vibration energy. The propagation and attenuation of different vibration amplitudes and frequencies in fresh concrete were investigated at different distances from the vibration source. The findings showed that the mixture design did not influence the attenuation of vibration. Mixtures containing coarse aggregates were successfully 3D printed using a prototype vibrating nozzle. Mixtures that were successfully 3D printed were found to have a slump between 1 – 1.5 in. and a drop table spread of 3 – 3.5 in. Rheological limits for successful 3D printing were then established by using regression analysis. Finally, a framework for 3D printing using a vibrating nozzle is proposed. Based on the performance of a trial mixture and potential issues faced while 3D printing, various possible changes that could be made to the mixture is outlined.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Pattaje Sooryanarayana, Karthik

Contributors dc:contributor

• Lange, David A
• Popovics, John S
• Roesler, Jeffery R
• Garg, Nishant
• Henschen, Jacob D

• 3d Printing
• Aggregates
• Rheology
• Yield Stress
• Icar
• Vibration

Statement dc:rights

• Copyright 2023 Karthik Pattaje Sooryanarayana

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/120206

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F120206