Reinforced Concrete: Correlation Between Cracking and Corrosion

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Title: Reinforced Concrete: Correlation Between Cracking and Corrosion

Author(s): Raoul Francois and Ginette Arliguie

Publication: Special Publication

Volume: 126

Issue:

Appears on pages(s): 1221-1238

Keywords: concretes; corrosion; cracking (fracturing); microcracking; reinforced concretes; Materials Research

Date: 8/1/1991

Abstract:
Determines the relationship between the cracking in loaded reinforced concrete and the corrosion of embedded steel. The test specimens used in this work are 3 m long beams and their constructive dispositions and loadings are in conformity with French specifications (BAEL 83). A salt fog and gas mixture with the same percentage of carbon dioxide and atmospheric air are the two aggressive environments. The authors use the single-replica technique, which enables crack openings of 0.1 micrometer to be discerned by scanning electronic microscope. The loadless initial state of concrete and the load damage state after bending can also be described. At this resolution, the reinforced concrete beams exhibit an absence of microcracks in both initial and loaded states. The study of the diffusion aggressive ions in concrete allows the microstructural state of cement paste-aggregate interfaces to be defined. The authors conclude that damage of the aureole of transition in the tensile zone of bending beams occurs. The aggressive ions quickly reach the reinforcement through the cracking, whatever their widths, and then progress along the embedded tension steel. The influence of concrete cover is clearly proved, as well as the aggressive difference between conservation environments. The authors follow the corrosion development by using steel electrode potential measurements. Previous results are corroborated; in particular, crack existence appears to be an essential parameter but not crack width. The aggressive environment is an important factor that should be taken into consideration by building regulations. Concrete thickness cover is also important, as well as its permeability, but the latter cannot be studied due to the use of only one concrete composition.