Durability of Loaded Reinforced Concrete in Chloride Environment

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Title: Durability of Loaded Reinforced Concrete in Chloride Environment

Author(s): R. Francois and G. Arliguie

Publication: Special Publication

Volume: 145

Issue:

Appears on pages(s): 573-596

Keywords: beams (supports); chlorides; corrosion; cover; cracking (fracturing); damage; durability; flexural strength; loads (forces); reinforced concrete; scanning electron microscope; Structural Research

Date: 5/1/1994

Abstract:
The object of this publication is to determine the relationship between the cracking in loaded reinforced concrete and the corrosion of embedded steel. Paper deals with the synthesis carried out for 7 years on reinforced concrete elements kept in a loading state, in a confined salt fog. The test specimens are 3-m-long beams, which is a sufficient size to be representative of the actual operating conditions of the reinforced concrete structures. Steel electrode potential measurements are performed on all beams kept in a salt fog environment to evaluate the state of the steel corrosion by a nondestructive way. The development of damage in concrete specimens is monitored by means of a scanning electronic microscope. The bending of the beams leads to the development of cracks that are neither preceded nor accompanied by microcracks, but the cement paste-aggregate interfaces are damaged in the tensile areas. On the other hand, the corrosion of steel leads to a secondary cracking that is branched out. Chloride penetration in concrete is obtained by measuring out free chlorides and bound chlorides in different samples extracted from different locations of the beams. Then, several parameters are studied, such as the effect of the location of the beam in the storage enclosure, the loading state of the beam area, and the intensity of the mechanical stress applied. Moreover, a relation is established between the rate of free chlorides measured and the embedded steel corrosion. The rate of corrosion is influenced by the concrete cover thickness even in the presence of cracks.