Creep of Mass Concrete at Early Ages

Smith, Donald M.; Hammons, Michael I.

doi:10.1061/(asce)0899-1561(1993)5:3(411)

Cited by 3 publications

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“…Therefore, in order to predict the risk of cracking in concrete elements, it is important to focus on the mechanical properties of concrete in tension, and particularly on its delayed behavior, the effects of which (cracking or stress relaxation) are not yet well understood. Since Freyssinet highlighted the creep of concrete in France in 1912, regardless of Hatt's findings in the United States in 1907 [3], the phenomenon has been extensively studied, as shown by the numerous publications on this topic (see [4][5][6][7][8][9][10] for example).However, due to the difficulties of performing a tensile test on cement-based materials [11], particularly for fixing of the samples to the loading device [12] and measuring the values of the strains, which are too small for most extensometers to cope with, the majority of experimental studies on concrete creep have dealt with compressive creep. When experiments involve tensile creep of cement-based materials, the tests are usually limited to early age behavior [11,[13][14][15][16][17][18][19][20][21][22][23].…”

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Basic creep of concrete under compression, tension and bending

Ranaivomanana

Multon

Turatsinze

2013

Construction and Building Materials

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Investigations on concrete creep are often limited to the compression behavior due to the difficulty of performing tensile tests on cement-based materials. This paper describes the experimental setup developed to achieve direct tensile and bending concrete creep. The precautions taken to obtain relevant data are described. For comparison, tensile, flexural and compressive basic creep test were conducted in parallel. Although the approach is still controversial, the basic creep strain was determined by subtracting the shrinkage strain and instantaneous strain from the total strain. Results available for specimens subjected to 50% of the strength in tension or in compression are presented. The final discussion compares the basic creep under the different types of loading.Because of its poor strain capacity and low tensile strength, concrete is brittle and highly sensitive to cracking. In most cases, cracks can significantly reduce the lifetime of a structure by allowing the ingress of aggressive agents. Cracks have various origins, which are all associated with the existence of extensions: effect of external loading, physicochemical pathologies leading to the formation of new expansive products (Alkali-Aggregate Reaction -AAR, Delayed Ettringite Formation -DEF, corrosion). A non-uniform state of deformation associated with thermal or hydric gradients or restrained strain in bonded cement-based overlays induce built-in tensile stresses which can also initiate cracking. The heterogeneity of concrete also plays an important role in the mechanism of crack formation. Even if a specimen is tested in compression, the first damage that occurs at the paste-aggregate interface is the consequence of tensile stresses resulting from the differences between the two phase moduli (for paste and aggregate) and from the interfacial transition zone (ITZ) [1], which has limited mechanical performance. According to Liners [2], the application of a compressive preload on a specimen can generate damage in tension, resulting in a significant drop in the tensile strength of up to 50% depending on the level and the duration of loading application. Therefore, in order to predict the risk of cracking in concrete elements, it is important to focus on the mechanical properties of concrete in tension, and particularly on its delayed behavior, the effects of which (cracking or stress relaxation) are not yet well understood. Since Freyssinet highlighted the creep of concrete in France in 1912, regardless of Hatt's findings in the United States in 1907 [3], the phenomenon has been extensively studied, as shown by the numerous publications on this topic (see [4][5][6][7][8][9][10] for example).However, due to the difficulties of performing a tensile test on cement-based materials [11], particularly for fixing of the samples to the loading device [12] and measuring the values of the strains, which are too small for most extensometers to cope with, the majority of experimental studies on concrete creep have dealt with compressive creep. When experimen...

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Basic creep of concrete under compression, tension and bending

Ranaivomanana

Multon

Turatsinze

2013

Construction and Building Materials

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“…Since then much has been found about the physical nature and mechanisms of the phenomena [21][22][23][24] and several mathematical laws to determine the relationship between strain and stress over time are available [19,[25][26][27][28][29]. However, the composition of dam concrete, with large fly ash content and large aggregates, requires more research regarding the hydration and aging processes and the calibration of the existing model with specific experimental results [30][31][32][33].…”

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Dam and wet-screened concrete creep in compression: in situ experimental results and creep strains prediction using model B3 and composite models

2016

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This paper proposes a methodology for the prediction of the compressive creep strains of dam concrete based on wet-screened experimental results at constant elevated temperature conditions measured in situ. Due to its large aggregate dimensions, the experimental characterization of dam concrete has particular constraints. The wet-screened concrete, obtained by sieving the aggregates larger than a given dimension, after mixing, is used to cast standard specimens and to embed monitoring devices. An experimental in situ installation using creep cells was used to obtain the compressive creep strain development over time for the maturing conditions of the dam core. The study of the effect of wet-screening procedure on creep in compression considers three types of concrete, dam concrete and two wet-screened concretes tested at three loading ages, 28, 90 and 365 days. The comparison between different types of concrete at different maturing conditions requires the definition of a reference state given by the maturity method, using the equivalent age, and relies on the fit of compressive creep strains to the RILEM recommended model B3. To take into account the effect of the aggregate content on the deformability properties of dam concrete, an equivalent two-phase composite model was applied. The equivalent composite model considered the equivalent matrix as the wet-screened concrete and the inclusions as the larger aggregates that are removed during the wet-screening procedure. Predictions obtained with the composite model are close to the dam concrete experimental results, for the tested loading ages.

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