Materials and Structures/Materiaux et Constructions, 1991,24,409-421 Improved prediction model for time-dependent deformations of concrete: Part 2-Basic creep

The second part ()f this series presents the formulae for the prediction of basic creep of concrete, i.e. creep at no moisture exchange. The formulae give the secant uniaxial compliance function It'hich depends on the stress level, and, as a special case, the compliance function for linear structural analysis according to the principle of superposition. The formulae are hased on the recently developed solidification theory for concrete creep which takes into accollllt simultaneous ageing, sati4ies all the hasic thermodynamic requirements, and avoids dil'ergence of ' creep curves. The formulae, which descrihe both creep and elastic properties, inroll'e only fiJl/r fj'ee material parameters. All four appear linearly, so that optimum data/its can he ohtained hy linear regression. For the frequent situations where no test data for the particular concrete to he used are available, empirical formulae for predicting these four parameters fi'om the COllerete mix composition alld the standard compressive strength are given. These formulae, however, involve considerable error. To avoid it, one should, whenever possible, carry out measurements of the elastic modulus and, if possible, also the short-time creep of 7 to 28 days duration. With such measurements, greatly improved predictions can be achieved. The predictions are compared with 17 extensive data sets taken from the literature