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The effect of ambient temperature and humidity to which concrete is exposed prior to or during loading should be taken into account; when creep and shrinkage are predicted. The purpose of this study is to clarify the effect of ambient temperature and humidity on the creep and shrinkage of concrete. In this study, we carried out creep and shrinkage tests under constant and varying histories of temperature and humidity. Creep and shrinkage tests sub-jected to ambient temperature and humidity were also carried out in the room where the effect of rain and wind were negligible. The effect of temperature on shrinkage is much bigger than that of changes in humidity. The shrinkage strain on concrete subjected to increase in temperature is much bigger than that measured under constant temperature. The magnitude of creep and shrinkage is highly influenced by the difference of the season in which concrete is cast. The effect or variance of humidity on creep seems to be small. The temperature of curing water before application of load significantly influenced creep of concrete.

This paper, supplementing the exposition of model B3 in this volume, examines various basic questions in formulating and evaluating a prediction model for creep and shrinkage of concrete. Verification by comparisons to a few subjectively selected data sets is no longer justifiable because computers have made statistical comparisons to the existing internationally accepted compre-hensive data bank very easy. The statistics based on the data bank alone, however, are insufficient. There are three further criteria: (1)After optimizing its coefficients, the prediction 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, physically justified theoretical basis, and (3) should allow good and easy extrapolation of the short-time tests into long times, at high ages at loading, large thicknesses etc. The last criterion is paramount because good long-time predictions can be achieved only through updating based on short-time data for the given par-ticular concrete. Various aspects of the B3 model and the GZ model (also appearing in this volume), 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 their advantages and differences.

A simple model for the characterization of concrete creep and shrinkage in design of concrete structures is proposed. It represents a shortened form of model B3 which was presented in [2] (as and improvement of the original version [3]) and appears in this volume, and an update of a previous short form [4]. The main simplification compared to model B3 comes from the use of the log-double-power law as the basic creep compliance function. The B3 formulae for predicting material parameters in the model are simplified by dropping the dependence of these parameters on the composition of concrete mix, leaving only dependence on the strength and the specific water content of the concrete mix. The model is justified by statistical comparisons with all the data in the internationally accepted RILEM data bank. The differences be-tween the present short-form and model B3 are discussed and limitations of the short form are compared to model B3 are noted. The model is suitable for design of concrete structures with the exception of highly creep-sensitive struc-tures for which the full model B3 is necessary

This paper presents a simple design-office procedure for calculating the shrinkage and creep of concrete using the information available at design; namely the 28 day specified concrete strength, the concrete strength at end of curing or loading, element size and the relative humidity. The method includes strength development with age, relationship between modulus of elasticity and strength, and equations for predicting shrinkage and creep. The only arbitrary information are the factors appropriate to the cementitious material, which can be improved from measured strength age data. At the most basic level the proposed method requires only the information available to the design engi-neer. The prediction values can be improved by simply measuring concrete strength development with time and modulus of elasticity. Aggregate stiffness can be taken into account by back calculating a concrete pseudo strength from the measured modulus of elasticity. Measured short term shrinkage and creep values can be extrapolated to obtain long duration predictions for simi-lar sized elements. The predictions are compared with experimental results for seventy nine data sets for compliance and sixty three data sets for shrink-age. The comparisons indicate shrinkage and creep can be calculated within +/- 25%. The method can be used regardless of what chemical admixtures or mineral by-products are in the concrete, casting temperature or curing regime.

This paper discusses possible mechanisms of basic creep and autogenous shrinkage and their couplings. The starting point is a kinetics analysis of the basic creep of different types of concrete, a normal strength concrete and a high performance concrete. This approach reveals two domains: short term creep kinetics, active for some days after loading, and long term creep kinet-ics, characterized by a pronounced and non-asymptotic aging. Then, by ex-ploring the creep-shrinkage interaction under sealed conditions, we confirm that the long term autogenous skrinkage, which cannot be explained by pure hydration effects, can be associated with a matrix creep under internal pore pressure. This pressure seems to depend mainly on the water:cement ratio. Finally, we present some preliminary experimental results on the creep dila-tancy behavior of concrete. The results indicate that the short term creep is characterized by a viscous dilatant behavior (i.e., positive volume increase rate), while the long term creep is of rather non-dilatant nature occurring at constant volume.