17. SCC flowability: Effect of changes in particle surface area, and how to compensate for this

Title: 17. SCC flowability: Effect of changes in particle surface area, and how to compensate for this
Author(s): O. Esping
Paper category : conference
Book title: 5th International RILEM Symposium on Self-Compacting Concrete
Editor(s): G. De Schutter and V. Boel
Print-ISBN: 978-2-35158-047-9
e-ISBN: 978-2-35158-088-2
Publisher: RILEM Publications SARL
Publication year: 2007
Pages: 123 - 130
Total Pages: 8
Nb references: 10
Language: English

Abstract: Due to the large particle surface area, quantification of fillers and the fine part of aggregates is essential for the ability to control physical properties, such as workability of self-compacting concrete. In the presented work, the effect of the specific surface area of gravel and limestone filler on the rheology of self-compacting concrete has been evaluated. The surface area was measured with a simplified BET-method, using water as adsorbate. A model is presented, where a change in specific area by BET(H2O) is translated to a change in water demand for the concrete mix. The model is based on an assumption that 30 full molecular layers of water, covering the particle surface is required to decrease interactions and provide lubrication, sufficient to create flowability. The results indicated that a change in BET(H2O)-area of 1000 m2/kg corresponds to approximately 0.8% moisture content of the gravel. E.g. a SCC with 1000 kg gravel (0-8 mm) that increases by 1000 m2/g in area will need 8.5 litre extra water, in order to retain its consistency. In cases where traditional methods for geometrical characterization (size distribution, water absorption, modulus of fineness, etc.) is kept within acceptance a normal gravel for concrete can vary by up to 7000 m2/kg in surface area.

Online publication: 2009-06-16
Publication type : full_text
Public price (Euros): 0.00