26. Tailored yield stress for 3D printing using Low clinker cement – LCC3D

Principal investigator(s) – PI

• Dr. rer. nat. Daniel Jansen
  Friedrich-Alexander Universität Erlangen-Nürnberg, GeoZentrum Nordbayern – Lehrstuhl für Mineralogie
  
• Prof. Dr. Jürgen Neubauer
  Friedrich-Alexander Universität Erlangen-Nürnberg, GeoZentrum Nordbayern – Lehrstuhl für Mineralogie
• Prof. Dr. rer. nat. Dietmar Stephan
  TU Berlin, Institut für Bauingenieurwesen FG Baustoffe und Bauchemie

Researcher(s) in-charge – RI

• M.Sc. Clemens Ehm
  Technische Universität Berlin, Institut für Bauingenieurwesen FG Baustoffe und Bauchemie
  
• M.Sc. Cordula Jakob
  Friedrich-Alexander Universität Erlangen-Nürnberg, GeoZentrum Nordbayern – Lehrstuhl für Mineralogie
• M.Sc. Ursula Pott
  Technische Universität Berlin, Institut für Bauingenieurwesen FG Baustoffe und Bauchemie
• M.Sc. Julian Wolf
  Friedrich-Alexander Universität Erlangen-Nürnberg, GeoZentrum Nordbayern – Lehrstuhl für Mineralogie

Subject Areas

Construction Material Sciences, Chemistry, Building Physics

Term

Since 2021

Project identifier

Deutsche Forschungsgemeinschaft (DFG) – Projektnummer 386869775

Project Description

Environmental protection and the sustainable use of resources are two crucial goals of the present time. Due to the greenhouse gas CO₂, which is released during clinker production, the cement production contributes to ~3% of CO₂ emission in Germany and 6-8 % worldwide (WWF Deutschland, 2019; Schneider, 2019). To counteract the increasing problem, it is necessary to reduce CO₂ emission in the building sector. The report of the United Nations Environment Programme (UNEP) on “Eco-efficient cements: Potential economically viable solutions for a low-CO₂ cement-based materials industry“ (UN Environment et al., 2018) already presented the two most effective approaches. First, Portland cement (OPC) must be replaced by materials that produce less CO₂. This can be achieved by using so-called supplementary cementitious materials (SCM). Second, the amount of concrete in buildings has to be reduced. To achieve this, the use of concrete must be closer to the structural requirements and should only be used where it is necessary. This can, e.g., be achieved by the new technology of 3D printing (Schlueter et al., 2016).

One unsolved problem for mortars for 3D printing is the very high clinker demand compared to standard concrete (Buswell et al., 2018). The highest proportion of the binder content in printable concrete is made up of Portland cement CEM I (Chen et al., 2017). The high amount of clinker is caused by the low proportion of aggregates and is necessary for the interlayer connection as well as for the rapid strength development if high structures are printed in short times. Up to now, mainly standard OPCs are used for 3D printing with an addition of only 10-30 wt.-% of SCMs (Chen et al., 2017; Panda et al., 2018). Therefore, the experimental setup in the present application will be the use of specially designed mixtures based on the LC³ approach with a high substitution degree of OPC clinker.

The rheological properties (mainly yield stress) of printable mortars are influenced by the amount of ettringite and C-S-H, which is formed during deposition and elevation states. There are few publications dealing with controlled phase formation and in consequence tailored rheological properties of the mortar during the printing process up to now. For this reason, the investigation of the phase development and the influence of the printing process on it should be particularly examined. By this setup, we will be able to reach three goals:

1. Reduction of OPC in printable mortars with subsequent reduction of CO₂.
2. Fast and efficient 3D printing by steering the rheological properties of the mortar over time by a controlled phase formation.
3. In-situ monitoring of the rheological behavior of mortar during printing – fresh state property testing methods for printability, extrudability and buildability (Wangler et al., 2019; Nerella et al., 2019).

The construction sector has a significant influence on the current CO₂ emission and thus, there is a need to reduce it. CO₂ could be reduced by both using SCMs and 3D printing technology. For this reason, the interest and research potential in both areas is high. Up to this stage, there are many open questions, which will be addressed in our work. The objectives of the proposal arise from the following open questions:

1. Benchmarking rheology: What are the rheological parameters for successful 3D printing, and how can they be monitored? What is the process window for parameters like yield stress, plastic viscosity and thixotropy?
2. Understanding rheology: How do SCMs such as limestone and calcined clay or a combination of both affect the rheological parameters necessary for 3D printing? What is the influence of phase development (solid content), what is the influence of physically bound water (surface wetting)?
3. Tailoring rheology: How can we tailor yield stress for successful 3D printing of LC³ type cements by admixtures?
4. Printability: How can we manage to determine printability and buildability (yield stress) in real-time during the printing process?

References:
– Buswell, R.A.; Leal de Silva, W.R.; Jones, S.Z.; Dirrenberger, J.; 3D printing using concrete extrusion: A roadmap for research; Cem. Concr. Res. 112 (2018) 37-49
– Chen, Y.; Veer, F.; Çopuroglu, O.; A critical review of 3D concrete printing as a low CO2 concrete approach; Heron 62 (2017) 167-194
– Nerella, V. N.; Näther, M., Iqbal, A., Butler, M.; Mechterine, V.; Inline quantification of extrudability of cementitious materials for digital construction; Cem. Concr. Res. 95 (2019) 260-270
– Panda, B.; Unluer, C.; Tan, M.J.; Investigation of the rheology and strength of geopolymer mixtures for extrusion-based 3D printing; Cem. Concr. Compos. 94 (2018) 307-314.
– Schlueter, A.; Rysanek, A.; Miller, C.; Pantelic, J.; Meggers, F.; Mast, M.; Bruelisauer, M.; Wee, Ch., K.; 3for2: relizing spatial, material, and energy savings through integrated design, CTBUH J. (2016) 40-45
– Schneider, M.; The cement industry on the way to a low-carbon future; Cem. and Concr. Res. 124 (2019) 105792
– UN Environment, Scrivener, K.; John, V., M.; Gartner, E.M.; Eco-efficient cements: Potential economically viable solutions for a low CO2 cement based materials industry; Cem. Concr. Res. 114 (2018) 2-26
– Wangler, T.; Roussel, N.; Bos, F.P.; Salet, T.A.M.; Flatt, R.J.; Digital Concrete: A Review; Cem. Concr. Res. 123 (2019) 105780