Metal Casting Technology

Prepared by Udaybhan Singh RanaStudent Id: 104334971University of Windsor, ONSubmitted to Professor Jerry Sokolowski

Objective •Reinforcement corrosion in concrete

•Chloride induced corrosion •Carbonation induced corrosion

•Mechanical analysis of corrosion induced cracks

Comparison of crack propagationTensile stress distribution

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What is corrosion in reinforcement concrete?

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Overview

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In the high PH environment, a dense film of gamma-iron oxide, which acts as a passivating film, is formed on a surface.

Concrete is having a PH of around12-13.

At this high PH this passivating film is thermodynamically stable.

Iron in Concrete

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Chloride induced

Carbonation induced

Reinforcement corrosion in concrete

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Chlorides ingresses in the concrete from fine pores and further damage the passivating film.

Once this films ruptures, iron bar is exposed to the outside atmosphere, results in the initiation of corrosion.

Chloride induced reinforcement corrosion

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What happens next …? once corrosion is initiated, the corrosion products

continuously accumulate and subsequently the expansion effect induces cracking in the concrete and leads to rapid performance degradation of the structure.

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Model under experiment This corrosion process involves three

major issues:

The mechanical analysis of the cracking and its propagation in RC structural members.

the second issue involves various transport phenomena in concrete, such as temperature, humidity, chloride ions and oxygen and

The third is the electrochemical analysis for active corrosion in steel.

a>3C, results will independent of S,C rebar diameter.

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An experiment is performed and a finite element model is constructed in the software Abacus/Standard. This model provides a means for the recognition of crack patterns.

Cracks are first initiated at the concrete/steel interface, they mainly propagate along two directions: the vertical direction (path 1) and the 45 degree direction (path 2), as demonstrated in figure only when they fulfill

Mechanical analysis for corrosion induced cracking in concrete

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Comparison of crack propagation

VERTICAL CRACK Graph shows the penetration of

the crack front into the sound cover concrete along the vertical direction. As can be seen, it is not a monotonically outward propagation process, as the crack ends at point C. After cracks are first initiated at the concrete/steel interface (when ds = 0.00075 mm), the vertical crack soon appears on the concrete surface at ds = 0.00611 mm, while it penetrates through the concrete cover at ds = 0.07676 mm.

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Propagation of cracks along the 45 direction as radial displacement increases

When ds = 0.09263 mm, the inclined crack front reaches the concrete surface. These graphs provide a direct relationship between the imposed radial displacement ds and the crack propagation.

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Tensile stress distribution in concrete Larger tensile response of the

concrete occurs near the outer surface compared with the middle part of the concrete cover.

This is because of this tensile stress distribution that vertical crack propagates from concrete surface.

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Broomfield J (1997) Corrosion of steel in concrete, understanding, investigating & repair. E & FN Spon, London

Tanaka Y, Kawano H, Watanabe H (2006) Study on cover depth for prestressed concrete bridge in airborne-chloride environments. PCI J 51(2):42–53

Tuutti K (1982) Corrosion of steel in concrete (Tech. Rep.). Swedish Cement and Concrete Research Institute, Stockholm

Liu Y, Weyers RE (1998) Modelling the time-to-corrosion cracking in chloride contaminated reinforced concrete structures. ACI Mater J 95(6):675–681

Martin P (1999) Service life prediction of R.C. highway structures exposed to chlorides. Ph.D. thesis, University of Toronto, Canada

Li CQ (2003) Life cycle modeling of corrosion affected concrete structures-initiation. J Mater Civ Eng 15(6):594–601

References

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Further topics to be covered Method for diffusion analysis

Electrochemical analysis for active corrosion in steel

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Thank you