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51318-11584-CATHODIC PREVENTION-PROTECTION OF STEEL IN CRACKED CONCRETE

This work seeks to determine the performance of cathodic prevention (CPrev) and cathodic protection (CP) systems applied to cracked concrete in a simulated marine environment.

Product Number: 51318-11584-SG
Author: M. Dugarte / A.A. Sagüés
Publication Date: 2018
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Reinforcement steel in concrete corrodes severely in marine service when chloride ion concentration exceeds a critical threshold level (CT). Cathodic prevention (CPrev) has been proposed as a supplemental corrosion management approach to extend service life of structures under this severe environment. This work seeks to determine the performance of CPrev and cathodic protection (CP) systems applied to cracked concrete in a simulated marine environment. Experiments use reinforced concrete blocks with controlled-width cracks placed along the length of a central reinforcing steel bar, with initial cyclic exposure to a 5% NaCl solution. Crack widths ranging from 0.01 in to 0.04 in (0.25 mm to 1 mm) and polarization levels ranging from -330 mV to -540 mV (SCE) were evaluated for cathodic prevention over a 3.5 year exposure period. Specimens without any protection served as open circuit potential (OC) controls. Time to corrosion initiation increased substantially as polarization reached -540 mV (SCE), with 4 instances of no activation at that potential after >1300 days of continuing exposure, including even one instance with the widest crack (0.04 in). Interpretation of the results with an empirical equation fit procedure tentatively projected extended cathodic prevention in the presence of cracks up to 0.04 in at a polarization potential somewhat beyond (e.g., ~ -0.56 V (SCE)) the most negative values examined here. Long term verification of that projected limit is needed.

 

Key words: cathodic prevention, cathodic protection, steel corrosion, cracked concrete, chlorides.

Reinforcement steel in concrete corrodes severely in marine service when chloride ion concentration exceeds a critical threshold level (CT). Cathodic prevention (CPrev) has been proposed as a supplemental corrosion management approach to extend service life of structures under this severe environment. This work seeks to determine the performance of CPrev and cathodic protection (CP) systems applied to cracked concrete in a simulated marine environment. Experiments use reinforced concrete blocks with controlled-width cracks placed along the length of a central reinforcing steel bar, with initial cyclic exposure to a 5% NaCl solution. Crack widths ranging from 0.01 in to 0.04 in (0.25 mm to 1 mm) and polarization levels ranging from -330 mV to -540 mV (SCE) were evaluated for cathodic prevention over a 3.5 year exposure period. Specimens without any protection served as open circuit potential (OC) controls. Time to corrosion initiation increased substantially as polarization reached -540 mV (SCE), with 4 instances of no activation at that potential after >1300 days of continuing exposure, including even one instance with the widest crack (0.04 in). Interpretation of the results with an empirical equation fit procedure tentatively projected extended cathodic prevention in the presence of cracks up to 0.04 in at a polarization potential somewhat beyond (e.g., ~ -0.56 V (SCE)) the most negative values examined here. Long term verification of that projected limit is needed.

 

Key words: cathodic prevention, cathodic protection, steel corrosion, cracked concrete, chlorides.

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