Abstract
A new experimental approach that allows separation of the components of the Pickett effect due to surface microcracking and stress-induced shrinkage is developed and demonstrated for early age concrete subjected to tensile loads induced in restrained shrinkage tests. The experiment measures creep of three concree materials subjected to same loads, but under different environments: moist-cover, sealed, and drying conditions. The key features of the experiment are the suppression of shrinkage in the moist-cover test, and the uniform internal drying in the sealed test. The results confirm that the Pickett effect in tension has two sources: stress-induced shrinkage and microcracking. The new approach provides insght to creep, shrinkage, softening, and cracking behaviour under tensile load, and explains behavioral differences between plain and fiber reinforced concrete.
Résumé
Une nouvelle approche expŕimentale permettant la séparation des composants de l'effet de Pickett dû à la microfissuration extérieure et au retrait provoqué par la traction est développée et démontrée pour le béton au jeune âge soumis à traction lors d'essais sous retrait restreint. L'expérience mesure le fluage de trois matériaux à base de béton soumis aux mêmes chargements, mais sous différents environments, à savoir en condition d'humidité, en condition étanche et en condition de séchage. Les principales caractéristiques de l'expérience sont la suppresion du retrait dans l'essai en conditions d'humidité et le séchage interne uniforme dans l'essai en condition étanche. Les résultats confirment que l'effet de Pickett en traction a deux sources: le retrait provoqué par la traction et la microfissuration. Cette nouvelle approche fournit un aperçu sur le fluage, sur le retrait, sur le radoucissement et sur les comportements de déformations sous chargement en traction, et elle explique les différences de comportement entre le béton normal et le béton renforcé de fibres.
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Editorial Note Prof. David A. Lange is a RILEM Senior Member. He participates in the work of RILEM TC 181-EAS ‘Early age shrinkage induced stresses and cracking in cementitious systems’.
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Altoubat, S.A., Lange, D.A. The Pickett effect at early age and experiment separating its mechanisms in tension. Mat. Struct. 35, 211–218 (2002). https://doi.org/10.1007/BF02533082
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DOI: https://doi.org/10.1007/BF02533082