Effect of varying CA2/CA ratios in Calcium-Aluminate-Calcite-mixtures analysed by combined QXRD, µ-CT and flexural-strength testing

Goergens J, Belli R, Schulbert C, Götz-Neunhoeffer F (2022)


Publication Language: English

Publication Type: Conference contribution, Abstract of a poster

Publication year: 2022

Event location: Karlsruhe DE

Abstract

Common calcium aluminate cements (CAC) may vary in their CA2 to CA ratio. While CA is the main phase of most CACs and is responsible for the initial strength, the CA2 phase has also received more attention in the last few decades. The reason for this is the higher Al-content of CA2 and thus the ability to produce more AH3 than CA as well as a higher thermic stability. In Calciumsulfoaluminate-cements (CSA), AH3 is considered to promote strength [1]. A gradual increase in the CA2 content and thus a change in the CA2/CA ratio in the clinker in CAC can be achieved by mixing of two cements, one CA-rich and one CA2-rich CAC. According to this approach, two industrial CACs were mixed in this work and six different CA2/CA-ratios were analysed with the following methods: QXRD after 1, 7 and 28 days of hydration demonstrates the quantitative progress of hydration, the clinker phase hydration degree as well as changes in AH3 and other hydrate phase quantities over time. Micro-computer tomography (µ-CT) of selected mixtures after 28 days enables a three-dimensional, non-destructive view of the inside of the sample, porosity and density heterogenities. The newly introduced B3B-method [2] for testing of the flexural strength in combination with the data evaluation according to Weibull (all mixes after 7 and 28 days) allows an interpretation of the mechanical properties. The combination of these three methodologies reveals that the mechanical properties deteriorate significantly from a CA2/CA ratio of 70:30 on to higher ones. The reasons for this are the macro-porosity, insufficient amounts of CA in the non-hydrated residue and differences in viscosity.

 

[1] Chang J, Zhang Y, Shang X, Zhao X, Yu X. Effects of amorphous AH3 phase on mechanical properties and hydration process of C4A3š-CšH2-CH-H2O system.  Construction and Building Materials 2017:133:314–322.

[2] Börger A, Supancic P, Danzer R. The ball on three balls test for strength testing of brittle discs: stress distribution in the disc. J Eur Ceram Soc. 2002;22:1425-36.

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APA:

Goergens, J., Belli, R., Schulbert, C., & Götz-Neunhoeffer, F. (2022, September). Effect of varying CA2/CA ratios in Calcium-Aluminate-Calcite-mixtures analysed by combined QXRD, µ-CT and flexural-strength testing. Poster presentation at 4th International Conference on the Chemistry of Construction Materials - ICCCM 2022, Karlsruhe, DE.

MLA:

Goergens, Julian, et al. "Effect of varying CA2/CA ratios in Calcium-Aluminate-Calcite-mixtures analysed by combined QXRD, µ-CT and flexural-strength testing." Presented at 4th International Conference on the Chemistry of Construction Materials - ICCCM 2022, Karlsruhe 2022.

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