ABSTRACT
The characteristics of long-term deformation of the new concrete to be used in underpinning must create as little impact as possible on the existing structure (compatibility of relative deformations). The evolution of time-dependent deformations has never been used as a selection criterion. The researchers used that criterion in designing the height increase of the Minaret of the Great Hassan II Mosque in Morocco. The chapter provides a comparison between the Beton Precontraint aux Etats Limites (BPEL, limit state design of prestressed concrete) laws and the predictive laws derived experimentally, which describe the behavior of high performance concrete containing silica fume. The BPEL code is based on a law describing much more gradual evolution of shrinkage. The Code shows that the coefficient of creep decreases much more slowly as a function of concrete age at loading than the decrease observed on the high peformance concretes studied.
