75. Effect of stabilizers on thixotropy and reduction of formwork pressure

Title: 75. Effect of stabilizers on thixotropy and reduction of formwork pressure
Author(s): S. Oesterheld, O.H. Wallevik
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: 497 - 502
Total Pages: 6
Nb references: 5
Language: English

Abstract: Self-compacting concrete (SCC) is prone to generate more pressure on formwork than conventional vibrated concrete, thus demanding more robust formwork. Normally the hydrostatic pressure is used for the calculation of formwork pressure when applying SCC.
This project deals with use of stabilizers (ST), also known as viscosity enhancing agents (VEA), in order to reduce formwork pressure, thus achieving more economical formwork.
The STs are expected to increase the thixotropy of the mixes. Thixotropic materials, here mortar and concrete, build after placing an internal structure, which should result in lower form pressure. Their effect is usually stated as actual form pressure relative to corresponding hydrostatic pressure.
The effect of the STs was measured through thixotropy in mortar and concrete mixes, using ConTec Viscometers 5 and 6 as rheology measuring devices. STs of different types were evaluated for their effect on rheological properties in mortars and, if promising, also in SCCs. Only a few of them showed considerable increase in thixotropy. Two of those which also effected favourably on bleeding and segregation were tested further in concrete mixes.
The actual form pressure reduction was measured in a column of 0,1 x 0,1 x 4,0 m. The maximum pressure reduction attained was around 40 % of hydrostatic pressure.

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