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Influence of bar diameter on top-bar effect in self-compacting concrete



Title: Influence of bar diameter on top-bar effect in self-compacting concrete
Author(s): P. Desnerck, G. De Schutter, and L. Taerwe
Paper category : conference
Book title: International RILEM Conference on Advances in Construction Materials Through Science and Engineering
Editor(s): Christopher Leung and K.T. WAN
ISBN: 978-2-35158-116-2
e-ISBN: 978-2-35158-117-9
Publisher: RILEM Publications SARL
Publication year: 2011
Pages: 239 - 246
Total Pages: 8
Nb references: 9
Language: English


Abstract: Settlement and bleeding of fresh concrete cause the formation of voids under horizontal reinforcement bars and reduce steel-concrete bond. The reduction in bond with horizontally embedded bars located in the upper sections of structural elements as opposed to those located near the bottom is known as the ―top-bar effect‖. It is caused by several factors including the properties of the concrete, the position and the shape of the bars, the methods of concrete placement, and the type of formwork.
This paper describes the results of a study carried out to assess the impact of the use of self-compacting concrete (SCC) on bond properties around steel reinforcement and the top-bar effect in columns and wall elements. Pull-out tests were carried out to determine bond strength between reinforcing steel bars and concrete. Two optimized SCC mixtures with slump flow values greater than 700 mm and a control concrete with a slump of 20-30 mm were investigated. The results showed that the maximum bond strength not always decreased when the diameter of the steel bar increased from 10 to 12 to 16 mm or when a lower strength class was used. The top-bar effect is clearly larger in the column made out of conventional vibrated concrete while the bond strengths in the SCC mixtures show little variations along the height of the column or wall.


Online publication: 2011-10-31
Publication type : full_text
Public price (Euros): 0.00