University of Natural Resources and Life Sciences, Vienna (BOKU) - Research portal
Gewählte Master / Diploma Thesis:
Stefan Gamel
(2009):
Bluten von Beton: Prognosemodell zur baustellennahen Abschätzung der Wasserabgabe.
Master / Diploma Thesis,
BOKU-Universität für Bodenkultur,
pp 134.
UB BOKU
obvsg
FullText
- Abstract:
- In the past years, bleeding of fresh concrete has become a major concern for quality in foundation engineering particularly for bored piles and diaphragm walls. Bleeding may give rise to poor quality of foundation works, e.g. large settlement of concrete, which is known as caries in bored piles; poor surface finishing in diaphragm wall reduced concrete cover. The susceptibility of concrete to bleeding is known to depend on the composition (concrete recipe) and pressure in fresh concrete. Concrete bleeding is also a concern in structure engineering. The testing method for concrete bleeding in structure engineering is described in the Austrian Standard EN 480-4. In foundation engineering the pressure is usually higher and the concrete softer. As a consequence, the standard EN 480-4 is not well suited for bleeding in foundation engineering. To meet the special needs in foundation engineering, a mobile testing device has been developed at BPV (Bautechnische Prüf- und Versuchsanstalt). The device consists of a pressurized chamber with a filter-outlet in the bottom. During the test, some readings of the amount of water squeezed out of the fresh concrete in the chamber are taken. A bleeding test will take about one hour. While this device presents an improvement to the testing method in EN 480-4, the testing time is still too long for some construction sites. In the present thesis, an empirical model is discussed, which allows a reliable prediction of the susceptibility to bleeding based on the testing results in the first 10 to 15 minutes. The model is based on the relationships in a single storage. Some correlations among the parameters are worked out. The calculations are summarized in diagrams, which allow easy handling and fast calculation on site.
- Beurteilende(r): Wu Wei