1 / 9

1. Concrete Corrosion Fundamentals

1. Concrete Corrosion Fundamentals. Reinforcement Protection by Passive Film. Ca, Na, K hydroxides in hydrated cement raise the pH to ~13.5 A dense protective  ferric oxide (Fe 2 O 3 ) passive film forms around the reinforcement

tacey
Download Presentation

1. Concrete Corrosion Fundamentals

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 1. Concrete Corrosion Fundamentals

  2. Reinforcement Protection by Passive Film • Ca, Na, K hydroxides in hydrated cement raise the pH to ~13.5 • A dense protective  ferric oxide (Fe2O3) passive film forms around the reinforcement • This passive film stops iron dissolution, and is stable at pH >10

  3. Causes of Reinforcement Corrosion

  4. Causes of Concrete Deterioration

  5. Causes of CorrosionChlorides • Airborne, marine, industrial, groundwater, cast-in • Cl– can penetrate through the passive film • At Cl- > “threshold”, passive film breaks down, corrosion initiates • Cl- “threshold” value is typically 0.05% by wt of concrete (0.02% prestressed concrete) • Pitting corrosion • Chlorides are main cause of reinforcement corrosion

  6. Causes of CorrosionCarbonation • CO2 gas dissolves in pore water  Carbonic Acid • Neutralises Alkalis in Concrete, pH ~ 9 • Passive Film dissolves • General corrosion starts

  7. Anodic Reaction (Oxidation) Fe  Fe2+ + 2e- Secondary Reactions Fe2+ Fe(OH)2, Fe3O4, Fe2O3 Corrosion Reactions Depassivation due to: Chlorides CO2 (carbonation) Cl- Cl- +ve Ions +ve Ions e- e- Anode Cathode Cathodic Reaction (Reduction) O2 + 2 H2O + 4 e-  4OH- High pH Maintained Anodes and Cathodes Oxygen & Moisture Oxygen & Moisture Fe Fe++ Rebar Cathode

  8. Rebar loss Spalling Cracks with Rust Staining Delamination Corrosion Damage

  9. Corrosion Damage

More Related