Analyzing the early structural build-up of accelerated cement pastes
| Autor: | Tobias Dorn, Tamino Hirsch, Dietmar Stephan |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Cement
Ettringite Vicat softening point Materials science Induction period 0211 other engineering and technologies 02 engineering and technology Building and Construction Calorimetry engineering.material 021001 nanoscience & nanotechnology Isothermal process chemistry.chemical_compound chemistry Mechanics of Materials ddc:540 021105 building & construction engineering Brownmillerite General Materials Science Extrusion Composite material 0210 nano-technology Civil and Structural Engineering |
| Zdroj: | Materials and Structures. 54 |
| ISSN: | 1871-6873 1359-5997 |
| Popis: | Extrusion-based additive manufacturing imposes high requirements on the material stability right after the extrusion. Therefore, a thorough understanding of the chemical reactions that determine the early reduction in processability is necessary. Accelerators are especially considered here, which have a major influence on the early reaction. This study contributes to these issues by analyzing the influence of 0.1 wt% TEA (triethanolamine) and 2.0 wt% Ca(NO3)2 on the hydration of two CEM I 52.5 R. The hydration was analyzed by isothermal heat flow calorimetry and in-situ X-ray diffraction. Vicat needle penetration, a penetrometer of own design, and ultrasonic P-wave velocity development were used to monitor the early change in workability. The obtained results indicate that ettringite formation is the main factor influencing workability during the first 60 min of hydration. Afterwards, the influence of ettringite is exceeded by the formation of C–S–H. Ca(NO3)2 was shown to enhance C–S–H formation and had no significant effect on the workability during the first 60 min of hydration while rapidly decreasing workability during the induction period. TEA was shown to increase brownmillerite dissolution and ettringite formation and, consequently, promote the workability loss during the initial hydration period. The time of initial and final setting determined by the Vicat needle test depended mainly on the formation of C–S–H phases. |
| Databáze: | OpenAIRE |
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