Sacrificial anode protection for rebar??
Sacrificial anode protection for rebar??
(OP)
I have a condominium project where lack of cover has resulted in the corrosin of rebar and spalling of the concrete surface of a few balconies. The floor is post tensioned with 10'-0" lengths of #4 bars placed at regular intervals perpidicular to the longitudinal joint between the balcony and the interior finished floor joint. (balcony is approx 5' in width) Post tensioned cables are running in both directions in general proximity of the area of distress.
At this point, the corroision has resulted in less than 10% section loss of the bar. However, due to aesthetic concerns with regards to surface spalling, its adverse affect on the balcony waterproofing, and additional section loss expected if nothing is done, I feel like action is required. The presence of multiple P.T. cables in various directions scares me out of excavating to provide the cover needed or installing a new dowel with adequate cover and remove the exposed portions of the existing. The presence of the exterior wall over the exact mid-length of the bar also creates problems with regards to a remove and replace situation. Door opening elevations will not allow additional topping to be placed over the bar.
That said does anyone have experience or suggestions with regards to attaching a sacrfical anode to the exposed bar to /reduce prevent continued deterioration. Has anyone had long-term success with corrosion inhibiting coatings? Suggestions regarding methods/procedures for protecting the bar and preventing further corrosion?
At this point, the corroision has resulted in less than 10% section loss of the bar. However, due to aesthetic concerns with regards to surface spalling, its adverse affect on the balcony waterproofing, and additional section loss expected if nothing is done, I feel like action is required. The presence of multiple P.T. cables in various directions scares me out of excavating to provide the cover needed or installing a new dowel with adequate cover and remove the exposed portions of the existing. The presence of the exterior wall over the exact mid-length of the bar also creates problems with regards to a remove and replace situation. Door opening elevations will not allow additional topping to be placed over the bar.
That said does anyone have experience or suggestions with regards to attaching a sacrfical anode to the exposed bar to /reduce prevent continued deterioration. Has anyone had long-term success with corrosion inhibiting coatings? Suggestions regarding methods/procedures for protecting the bar and preventing further corrosion?






RE: Sacrificial anode protection for rebar??
Vector Corrosion link
RE: Sacrificial anode protection for rebar??
http://www.sikaconstruction.com
RE: Sacrificial anode protection for rebar??
RE: Sacrificial anode protection for rebar??
RE: Sacrificial anode protection for rebar??
JW
RE: Sacrificial anode protection for rebar??
RE: Sacrificial anode protection for rebar??
Extending from 'pinehurst' comment, unbonded PT systems of yesteryear were often paper-wrapped or heat-sealed sheaths which have significantly less durability than the current extruded seamless HDPE sheaths. Additionally, it was common practice for 6+" lengths of un-sheathed strand behind the dead and live end anchorages - if such lengths are in exterior type exposures, with or without coastal chlorides, wire corrosion can occur.
With unbonded PT corrosion it often goes UNdetected for sometimes many years - ie minimal visual evidence of wire or strand failure. So whilst "There is no reason to suspect deterioration of the PT cables" we have seen many projects where a concrete repair contractor starts just rebar spall repairs and gets into some large $ PT repairs.
Also, concrete repair contractors doing just spall repairs without PT repair experincne can be dangerous. We have seen several contractors chip at slab/balcony edges for rebar/concrete spalls only to accidently de-tension live tendons. Be careful!
We have used FOSROC GALVASHIELD XP and CC imbedded anodes successfully - VECTOR CORROSION TECHNOLOGIEs have the license in North America and sublicense to MBT, SIKA etc.
A branch of ACI (Concrete Innovations Appraisal Service -CIAS) has done some technical research on these anodes with good success.
See==> h
RE: Sacrificial anode protection for rebar??
Core tests found that the salts had penetrated ALL of the slab, with the most concentration at the bottom of the slab and decreasing towards the top.
The lawsuit went on about ten years.