Prediction of the lateral pressure exerted by self-compacting concrete on formwork Y. Vanhove,  C. Djelal  and A. Magnin† Universite ´ d’Artois; Laboratoire de Rhe ´ologie, INPG This study concerns the prediction of lateral pressure exerted by self-compacting concrete (SCC) on formwork during the casting process. This estimation is obtained using Janssen’s model as used in the statics of ensiled granular material. The model has been adapted to SCC. The friction coefficient between the concrete and the wall occurring in the model is measured with a new type of tribometer. The case of SCC placed in 12 m high formwork by three companies using two different techniques is presented. Comparison of the predicted results with on site measurements shows good agreement. Notation A area of a formwork section e formwork thickness F mes interference friction force with fresh concrete friction force F par interference friction force g gravity acceleration h height h m maximal height of hydrostatic pressure K coefficient k reduction factor of the hydrostatic pressure L formwork width N normal force delivered by the pneumatic jack. P vertical pressure in the formwork P9 lateral pressure on the formwork P hyd hydrostatic pressure P concrete corrected pressure of Janssen’s model P Janssen pressure estimated by Janssen’s model S spread value with the slump test V Sliding velocity Æ correlation coefficient taking into account physical phenomena j internal friction angle r density of the material ô friction stress ô 0 yield shear stress ì friction coefficient Introduction One of the essential properties of concrete is its ability to fit the form into which it is poured before curing starts. In recent years the addition of new pro- ducts, notably admixtures, has opened the way for pre- viously impossible types of concrete. A new generation of concrete is in the news, known as self-compacting concrete (SCC). SCC is extremely fluid and has been developed for a number of reasons: reduced labour costs, improved working conditions, an end to noise caused by vibration, etc. On account of its high fluidity the lateral pressure exerted by SCC on formwork is different from conven- tional concrete. Overestimating pressure entails excess formwork costs. Underestimating pressure may cause deformation of structural elements or the collapse of formwork. Since 1950 there has been a growing determination to find a formula for calculating the pressure exerted by concrete on formwork. Quantitative laws have been established on the basis of extremely varied data, that are difficult to link, the aim being to identify the factors at work and determine their influence in so far as possible. 1–3 Magazine of Concrete Research, 2004, 56, No. 1, February, 55–62 55 0024-9831 # 2004 Thomas Telford Ltd  LAMH, Universite ´ d’Artois, Rue de l’universite ´, 62 408 Be ´thune cedex, France. † Laboratoire de Rhe ´ologie, INPG, UJF (Grenoble 1) CNRS UMR 5520, BP53 X, 38 041 Grenoble cedex, France. (MCR 1066) Paper received 25 July 2002; last revised 26 January 2003; accepted 4 June 2003.