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- Alkali-Kieselsäure-Reaktion (1)
- Alkali-silica-reaction (1)
- Automated testing (1)
- Baustoffe (1)
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- Drop-drop coalescence (1)
- Electrocoalescence (1)
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Eingeladener Vortrag
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Zur Vermeidung der schädigenden Alkali-Kieselsäure-Reaktion in Betonbauwerken wird die Alkalireaktivität von Gesteinskörnungen im Vorhinein getestet. Der 60°C-Betonversuch ermöglicht eine vergleichsweise schnelle Einschätzung nach fünf-monatiger Testzeit. Dazu wird die Dehnung von Betonprüfkörpern, die mit der zu testenden Gesteinskörnung hergestellt wurden, manuell alle 28 Tage gemessen. Ein alternatives, an der BAM in den vergangen Jahren entwickeltes Verfahren setzt Dehnungssensoren ein, um kontinuierlich und online zu messen. Die Dehnungskurven sind eine gute Grundlage sowohl für die Prognose vom Expansionsverhalten während des Tests als auch für die Validierung von Expansionsmodellen.
The concrete prism test at 60°C facilitates accelerated testing of alkali-silica reactivity of aggregates within five months. Manual measurement is usually conducted to determine expansion of test specimen every 28 days. This conventional procedure gives only limited insight to expansion behaviour of ASR-affected prisms. Due to the large time intervals, expansion exceeding the critical value of 0.3 mm/m is likely to be noticed late. Continuous recording applied in this work resolves this problem and delivers beneficial information on the shape of the expansion curve.
Different types of aggregate have been tested applying continuous and manual measurement to the concrete specimens.
Models of ASR-induced expansion, available in the open literature, so far are validated with discontinuous data hardly tracing the modelled curve. Continuous measurement improves validation and further model development.
Electrocoalescence of aqueous droplets in oil emulsions is commonly contemplated for enhancing separation.
High voltage electric fields can induce charges to Drops evoking merging of adjacent droplets. The newly formed larger Drops then sink faster in gravitational common settlers. Therefore, separation performance of an electrostatic coalescer is strictly linked to characteristics of the electric field and properties of the liquid−liquid system. In this work, the coalescence Performance of water droplets sinking in dodecane at a pulsed DC electric field is investigated. An experimental setup allowing the simultaneous injection of similar sized drops, setting of voltage and pulsation frequency, and particle tracking at high frame rate and resolution is designed. The generated data are used to check the validity of modeling approaches for drag, dipole−dipole forces, and film-thinning. Furthermore, CFD simulations are carried out using a volume of fluid method tracking the interfaces between the two phases.