Title: Creep and Shrinkage of High-Strength Field Concretes
Author(s): Francois Larrard
Publication: Symposium Paper
Appears on pages(s): 577-598
Keywords: creep properties; high-strength concretes; mathematical models; odels; self-desiccation; shrinkage; silica fume; Design
Two bridges, the Joigny and Pertuiset, have recently been built in France using high-strength concrete. It was necessary to measure the shrinkage and creep deformation of the concretes for their design. Two series of samples were taken, corresponding to the two kinds of concretes (one with and one without silica fume). The specimens were loaded at different levels and ages (including early ages). Some cylinders were carefully sealed to avoid any drying. Besides the mathematical equations deduced from these trials and detailed in the paper, the following results were discovered: the nonsilica fume high-strength concrete (HSC) is quite comparable to the normal strength concrete (NSC); during the setting, the silica fume HSC exhibits a certain autogenous shrinkage which is higher than that of the NSC concrete; for the silica fume HSC, the magnitude of the creep deformation is highly dependent on the age of concrete at loading, compared with elastic strains, so that the creep is much lower than for NSC (except when loading occurs at a very early age); regarding NSC, the theory of superposition applies fairly to the creep of high-strength concrete for nondecreasing loadings; and, finally, the desiccation creep is reduced for nonsilica fume HSC and entirely cancelled for silica fume HSC, meaning that creep does not depend on size for these materials. Some physical models are proposed at the paper's conclusion to explain these phenomena.