Form pressure generated by self-compacting concrete

Title: Form pressure generated by self-compacting concrete
Author(s): P. Billberg
Paper category : conference
Book title: International RILEM Symposium on Self-Compacting Concrete
Editor(s): O. Wallevik and I. Nielsson
Print-ISBN: 2-912143-42-X
e-ISBN: 2912143713
Publisher: RILEM Publications SARL
Publication year: 2003
Pages: 271 - 280
Total Pages: 10
Nb references: 11
Language: English

Abstract: It is quite obvious to presuppose that casting with self-compacting concrete, SCC, results in high form pressures because its extreme flowability showing nearly Newtonian behaviour, rheologically speaking. Thus, if the concrete has no significant yield stress it can even be assumed that a hydrostatic pressure will be reached. The assumption of very high form pressures is also supported by the fact that casting with such a flowable con-crete attracts one to increase the casting rate far beyond the level used when casting conventional con-crete. In many cases from around the world when the form pressure has been monitored using SCC it is indeed reported being very high. But sometimes, such as in several cases of bridge castings in Sweden, opposite results are reported, i.e., even lower pressures than the design values for conventional concrete. The SCCs used at these occasions have not deviated from the very fluid behaviour described earlier and still show the ability to withstand the load from concrete cast above it without increasing the horizontal pressure against the formwork to the same extent. Thus, it can be concluded that these SCCs behaves thixotropically meaning that while being forced into mo-tion (mixing, transportation, pumping and placing) it behaves as a liquid but builds up an inter-nal structure at rest. If the concrete is not allowed to rest, no such structure can be traced considering the same time-scale.
A project aiming at finding out parameters controlling the thixotropical properties of self-compacting bridge concrete has been performed between 1999 and 2002. Within this project, full-scale tests using a statically well-defined and monitored wall-form was performed and form-pressure were measured and evaluated according to different mix designs, form material, logis-tics and various casting techniques. The rate of casting dominated the influence of obtained form pressure. But also deviations from this correlation can be explained and attributed to concrete age and consistency.

Online publication: 2003-08-21
Publication type : abstract_only
Public price (Euros): 0.00