1. Home
  2. TRID
  3. View Record
https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

Kugelfallrheometer zur Pruefung von Selbstverdichtendem Beton / Falling-ball rheometer to prove self-compacting concrete

Selbstverdichtender Beton (SVB) ist im frischen Zustand zu Hochleistungen faehig. Seine speziellen Fliesseigenschaften erhaelt er durch ein im Vergleich zu konventionellem Ruettelbeton relativ grosses Moertelvolumen. Die Auswahl geeigneter Betonausgangsstoffe - vor allem fuer die Herstellung einer plastischen Moertelmatrix - entscheidet ueber die rheologischen Eigenschaften und somit ueber seine Leistungsfaehigkeit. Indem Zement durch Gesteinsmehl substituiert wird, laesst sich die Viskositaet des Moertels steigern und seine Festigkeit reduzieren. Zur Gewaehrleistung seiner Qualitaet verlangt SVB eine gruendliche Ueberwachung seines Fliessverhaltens. Da Frischbeton ein nicht-Newtonsches Medium ist, muss seine Viskositaet als Funktion der Schergeschwindigkeit bekannt sein. Zur Messung des scherspannungsabhaengigen Fliessverhaltens entwickelten die Autoren ein einfach anzuwendendes Rheometer. Das Messprinzip ist vergleichbar mit dem eines Kugelfallviskosimeters. Im Unterschied zum Viskosimeter wird bei dem neu entwickelten Messverfahren aus der Sinkgeschwindigkeit einer beschleunigenden Kugel eine Fliesskurve ermittelt. (A) ABSTRACT IN ENGLISH: Self-compacting concrete (SCC) is a high-performance concrete whose performance is predicated by the flow characteristics of the fresh concrete mix. In a fresh state, SCC may be viewed as a two-phase suspension containing coarse disperse aggregates as well as a viscous mortar that, when compared to conventional concrete, achieves its specific flow characteristics through a relatively high mortar content. The selection of appropriate raw materials - particularly for manufacture of plastic mortars - are essential factors in determining the rheological properties and thus performance of the concrete. By adding organic or inorganic admixtures, or a combination thereof, one may influence the flow characteristics of the mortar. Mix design for SCC is largely dictated by the rheological properties of the fresh concrete, such that the volumetric design approach, as used for conventional concrete with a given design compressive strength, is no longer applicable. This paper reviews the possibility to optimize the viscosity of mortar by replacing cement by rock powders with the objective to design SCC with normal strength. A research investigation has been conducted, investigating the effect of rock powders on flow characteristics of mortar matrices. Self-compacting concrete requires a careful control of its flow behaviour. Fresh concrete acts as a non-Newtonian fluid. It is insufficient to describe the rheological behaviour of non-Newtonian fluids with a conventional one-point workability test. Rheological measurements are essential to determine the flow behaviour dependent on the shear rate and to modify the mixture with the aim to achieve self-compacting properties. In order to measure the flow behaviour of SCC, the authors developed a rheometer which can be used simply. (A)

Language

  • German

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 01183492
  • Record Type: Publication
  • Source Agency: Bundesanstalt für Straßenwesen (BASt)
  • Files: ITRD
  • Created Date: Oct 7 2010 11:19AM