Criteria for Rational Prediction of Creep and Shrinkage of Concrete

Abstract. The paper discusses the problem of formulation and evaluation of a prediction model for creep and shrinkage of concrete. Verification by comparisons to a few subjectively selected data sets is no longer justifiable because comput-ers have made statistical comparisons to the complete existing data bank easy. However, statistics based on the data bank are insufficient. There are three fur-ther criteria: (1) After optimizing its coefficients, the model should be capable of providing close fits of the individual test data covering a broad range of times, ages, humidities, thicknesses, etc.; (2) the model should have a rational, physi-cally justified theoretical basis, and (3) should allow good and easy extrapolation of the short-time tests into long times, high ages, large thicknesses etc. The last criterion is very important because good long-time predictions can be achieved only through updating based on short-time data for the given particular concrete. Various aspects of the B3 and GZ models recently considered by ACI Committee 209, as well as some aspects of the CEF-FIP model, are briefly analyzed in the light of these criteria, clarifying the way to move ahead.