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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 13 Abstracts search results
May 1, 2000
D. J. Carreira and R. G. Burg
This paper summarizes most of the aspects and details related to testing for creep and shrinkage in concrete. The experimental determination of con-crete creep and shrinkage is discussed in detail, analyzing each of the condi-tions likely to be encountered during planning, testing and reporting test data. The subjects discussed are: objectives of test programs, test concept, as-sumptions, designing a test program, standard test methods for creep and shrinkage, test specimens, equipment for measuring deformations, concrete-mixing, batching and preparation of test specimens, testing environments, tem-perature and humidity tolerances, deformation measurement schedule, docu-mentation and interpretation of test results. Test programs are presented in detail. Field studies are discussed and correlated to laboratory test programs for three types structures sensitive in varying degrees to effects of creep and shrinkage. That is, field studies of reinforced and prestressed concrete nuclear containments, the uneven long-term shortening of columns with respect to the shear walls in reinforced concrete high rise buildings with shear walls, and the determination of prestressing forces, cambers, deflections and prestress loss in prestressed members.
Editor: Akthem Al-Manaseer / Sponsored by: ACI Committee 209
This Symposium Publication contains 12 papers presented at the Adam Neville Symposium in Atlanta, Georgia, in 1997. Topics relating to creep and shrinkage include admixture and cementitious materials effects, special high-performance considerations, temperature and humidity influences, reinforced and prestressed concrete analysis and design procedures, and much more.
Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order.
W. H. Dilger and C. Wang
Creep and shrinkage of concrete are important factors in the design and analysis of concrete structures, particularly for the long-term serviceability and durability and for the construction stage of long span, prestressed con-crete structures. Because of very low water-cementitious ratio (w/cm), chemical admixtures and sometimes mineral admixtures, the evolutions of moisture state and rate of cement hydration in high-performance concrete (HPC) are significantly different from those in normal concrete. For example, the cement hydration in HPC terminates earlier due to the lack of water, resulti ng in faster development of relative strength at early ages and little long-term strength gain. At the same time, self-desiccation in the form of a rapid decrease in internal relative humidity starts in HPC at very early ages. Consequently, base (autogenous) shrinkage of HPC is very high compared with normal concrete. The moisture permeability, which affects the development of creep and shrinkage of concrete, is at least one order smaller for HPC than for normal concrete. As a result well as creep and the development shrinkage property of strength and modulus of elasticity as es of HPC are remarkably different from those of normal concrete. The current prediction models for time-dependent properties, particularly creep and shrinkage, which have been derived from experimental data on normal concrete, are not applicable to HPC. This paper will discuss the main parameters affecting the time-dependent properties and the differences between HPC and normal concrete, based on the results of an extensive experimental program at the University of Calgary and data from the literature. A recently developed model to estimate creep and shrinkage of HPC is also presented and examined.
F. Ulm, F. Le Maou, and C. Boulay
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.
N. J. Gardner
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.
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