Restrained shrinkage of massive reinforced concrete structures: results of the project CEOS.fr

Within the CEOS.fr national research project, several experiments on massive concrete structures were conducted to improve the knowledge on the cracking phenomenon. In this paper, experiments where deformations at early age are restrained are presented. Testing bodies are I-shaped and two largely dimensioned steel struts are placed laterally between the two transverse heads to prevent almost any shrinkage. Three testing bodies were realized: RG8, the reference one; RG9, with a reduced reinforcement and RG10, with an increased cover. A full set of measurement was used for auscultation of these beams during early age. Optical long base fibres gave information on the relative displacement of the central part of the beam. Local measurements of strains in concrete were given thanks to Vibrating Wire Extensometers. Gauges on rebars produced data of the strain on the first reinforcement layer, and the force in struts was monitored. With this, the force and stresses in concrete and rebars could be deduced. This huge amount of data allows verifying the phenomenology of the concrete. Various hypotheses were analysed to explain the strain measured and the corresponding forces in each component during specific period of early age. A first analysis of the cracking process shows that the cracks could appear for stresses below the tensile strength.

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