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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 14 Abstracts search results
Document:
SP249-10
Date:
March 1, 2008
Author(s):
A.S. Ngab, F.O. Slate, and A.H. Nilson
Publication:
Symposium Papers
Volume:
249
Abstract:
The realtionship between tiem-dependent deformation and internal microcracking of high strength concrete was investigated experimentally. Direct comparison was made to the behavior of normal strength concrete subjected to similar relative uniaxial compressive stresses and under the same environment conditions. Sealed and unsealed specimens were analyed for microcracking after they were subjected to short-term loading, to shrinkage, and to sustained loading. Results confirm that microcracking, always present eve in unloaded specimens, is increased by short-term loading, shrinkage, and sustained loading. However, the amoutn of cracking, as well as the increase relative to the initial state, is significantly less in high strength concrete than in normal strength material. The amount of creep strain associated with internal cracking in high strength concrete is negligible, whereas such creep is significat in normal strength concrete, particularly at high stresses. The research also indicates that the ratio of the sustained load strength to the short-term strength is higher for high strength than for normal strength concrete. This also can be explained in terms of differences in microcracking. Time-dependent engineering properties for high strength concrete, such as creep coefficient, specific creep, and shrinkage characteristics, are reported in a separate paper.
DOI:
10.14359/20131
SP249-12
J.P. Romualdi and G.B. Batson
Due to copyright issues, this paper is only available by purchasing the SP-249. The application of linear-elastic fracture mechanics reveals that the strength of concrete in tension is limited by internal holes and micro-cracks. Fracture arrest can be achieved by reducing the spacing of reinforcement to a suitable scale. Reinforcement diameter decreases in proportion to reduction in spacing in order to maintain steel percentage. Theoretical results indicate that the tensile cracking strength of concrete increases in proportion to the inverse square root of the reinforcement spacing. Tests on closely spaced wire reinforced beams support the theoretical calculations.
Due to copyright issues, this paper is only available by purchasing the SP-249.
10.14359/20133
SP249-11
A. Hillerborg, M. Modeer, and P.E. Petersson
Due to copyright issues, this paper is only available by purchasing the SP-249. A method is presented in which fracture mechanics is introduced into finite element analysis by means of a model where stresses are assumed to act across a crack as long as it is narrowly opened. This assumption may be regarded as a way of expressing the energy absorption Gc in the energy balance approach, but it is also in agreement with results of tension tests. As a demonstration the method has been applied to the bending of an unreinforced beam, which has led to an explanation of the difference between bending strength and tensile strength, and of the variation in bending strength with beam depth.
10.14359/20132
SP249-13
T.C. Powers and T.L. Brownyard
This paper deals mainly with data on water fixation in hardened portland cement paste, the properties of evaporable water, the desnisty of the solid substance, and the porosity of the paste as a whole. The studies of the evaporable water include water-vapor-adsorption characteristics and the thermodynamics of adsorption. The discusssions include the following topics: 1. Theoretical interpretation of adsorption data 2. The specific surface of hardened portland cement paste 3. Minimum porosity of hardened paste 4. Relative amounts of gel-water and capillary water 5. The thermodynamics of adsorption 6. The energy of binding of water in hardened paste 7. Swelling pressure 8. Mechanism of shrinking and swelling 9. Capillary-flow and moisture diffusion 10. Esimation of absolute volume of solid phase in hardened paste 11. Specific volumes of evaporable and non-evaporable water 12. Computation of volume of solid phase in hardened paste 13. Limit of hydration of portland cement 14. Relation of physical characteristics of paste to compressive strength 15. Permeability and absorptivity 16. Freezing of water in hardened portland cement paste
10.14359/20134
SP249-05
D.A. Abrams
A discussion preceding a demonstration of actual field proportioning of concrete by Stanton Walker. Mr. Walker has prepared a resume of the methods used which appears on p. 182 of this volume.
10.14359/20126
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