Design Provisions for Shrinkage and Creep of ConcreteDesign Provisions for Shrinkage and Creep of ConcreteDesign Provisions for Shrinkage and Creep of Concrete

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Title: Design Provisions for Shrinkage and Creep of ConcreteDesign Provisions for Shrinkage and Creep of ConcreteDesign Provisions for Shrinkage and Creep of Concrete

Author(s): N. J. Gardner

Publication: Special Publication

Volume: 194

Issue:

Appears on pages(s): 101-134

Keywords: concrete; creep; modulus of elasticity; shrink-age; strength development

Date: 5/1/2000

Abstract:
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.