Surface Preparation
All loose and spalled concrete should be removed in accordance with ICRI Guideline No. 310.1R-2008 Guideline for Surface Preparation for the Repair of Deteriorated Concrete Resulting from Reinforcing Steel Corrosion. The Sika FerroGard® anode positioning should be considered when removing the existing concrete.
Preparation
For correct electrical connection and anode function, the surface of the reinforcing steel should be untreated and cleaned to a near white surface condition in areas designated for the connection of the FerroGard® anode. Refer to SSPC SP-10. Note, pre-soaking the SIKA FerroGard® anodes in clean water for several minutes prior to installation is recommended to minimize dehydration of the repair mortar.
Continuity
The reinforcing steel within the patch area should be tested for continuity: DC resistance between bars should be ≤ 1 Ω. Make continuity corrections, if needed, by welding steel bonding wire between bars to achieve a DC resistance ≤ 1 Ω.
Positioning
In most applications, the FerroGard® anode should be positioned at the perimeter of the repair and on plane with the reinforcing steel to provide a proper level of cover. Anodes must be positioned so that the entire anode and the wire connections to the reinforcing steel are totally covered by the repair material once the repair is complete. Note: Do not modify the shape of the anode to fit a hole.
Attaching
Tighten the two pairs of pre-twisted wires around the reinforcing steel in a double wrap pattern to achieve a sound electrical bond. The pre-twisted wire connectors provide a sound base, good electrical contact and proper spacing from the reinforcing steel to which the anode is attached. No additional form of attachment or electrical connection is necessary. Note: Use only the connector wires attached to the anode; do not use supplementary connection methods between the connector loops and the rebar nor use a twisting tool to tighten the wires.
Verification
Verify sound electrical connection of the FerroGard® system to the reinforcing steel by checking for a DC resistance ≤ 1 Ω.
Note: Conventional, commercially available repair mortars with a resistivity ≤50,000 Ω-cm should be used to repair the concrete and encase the FerroGard® anodes. Corrosion protection has been shown to be most enhanced when using mortars with a resistivity of ≤20,000 Ω-cm, however mortars with a resistivity up to 50,000 Ω-cm may be used. High polymer content and silica fume, which are known to have a resistivity >50,000 Ω-cm, should not be used in the mix. If the repair design requires a mix with resistivity >50,000 Ω-cm, then use an encasement mortar to encase the anode and bridge the area between the anode and the existing concrete. SikaRepair® 222 (with water) or SikaRepair® 223 (with water) are acceptable encasement mortars. Place encasement materials in accordance with conventional techniques to assure good consolidation.
Rebar coatings such as Sika Armatec 110 EpoCem and Sikadur 32 can and should be used along with Sika FerroGard anodes as full
system repair approach. The sketches below depict the proper way to install the rebar coating (and bonding agent). All the usual preparation techniques are employed (geometry of the repair area, cleaning the steel, surface preparation). The anodes are tied to the steel, continuity is verified and the rebar coating is applied as per the PDS. Please note, avoid coating the anode itself. The tie wires may be coated too as long as continuity to the steel is ensured.
Do not use any form of battery or impressed current in association with the FerroGard® anode or apply an electrical current to the reinforcing steel prior to or after the repair. Do not install a preformed high resistivity or non-conductive barrier between the FerroGard® anode and the reinforcing steel. Do not apply corrosion inhibitors directly on the FerroGard® anode body or connecting wires, especially on or near the wire connection point with the reinforcing steel.
Maximum Anode Spacing for Moderate-Low Corrosion Risk Environment
CI content <1% by weight of cement, or Steel Potential more positive than -350 mV, CSE
| Steel Density Ratio | Inches |
| <0.2 | 31 |
| 0.21-0.46 | 28 |
| 0.47-0.70 | 27 |
| 0.71-0.93 | 25 |
| 0.94-1.15 | 24 |
| 1.16-1.36 | 22 |
| 1.37-1.56 | 21 |
| 1.57-1.75 | 21 |
| 1.75-1.93 | 20 |
| 1.94-2.1 | 19 |
Maximum Anode Spacing for High Corrosion Risk Environment
Cl content >1% by weight of cement, or Steel Potential more negative than -350 mV, CSE
| Steel Density Ratio | Inches |
| <0.2 | 28 |
| 0.21-0.46 | 25 |
| 0.47-0.70 | 24 |
| 0.71-0.93 | 22 |
| 0.94-1.15 | 21 |
| 1.16-1.36 | 19 |
| 1.37-1.56 | 18 |
| 1.57-1.75 | 18 |
| 1.75-1.93 | 17 |
| 1.94-2.1 | 16 |
Common Steel Density Ratio Examples
| Bar Size | One Mat/One Way | Two Mat/Two Way |
| #4 | 0.13 | 0.52 |
| #5 | 0.16 | 0.65 |
| #6 | 0.20 | 0.79 |
| #7 | 0.23 | 0.92 |
| #8 | 0.26 | 1.05 |
Assumption: Bars are 12" On Center
Calculating Steel Density Ratio (Surface Area of Steel ÷ Surface Area of Concrete):
Surface Area of Steel ÷ Surface Area of Concrete
Surface area of steel = π x D x L x n
Surface area of concrete = 12” x 12” = 144 in2
π = 3.14
D = bar diameter
L = length of bars in calculated area (always 12” in this calculation)
n = number of bars in calculated area (12”÷ spacing)
Sample Calculation #1
Heavily Reinforced: #8 bars, 2 mats, 2 ways, 8” oc
Top mat, transverse: 3.14 x 8/8” x 12” x 12”/8" oc ÷ 144 in2 = 0.39
Top mat, longitudinal = 0.39
Bottom mat, transverse = 0.39
Bottom mat, longitudinal = 0.39
Total = 1.57
Sample Calculation #2
Moderately Reinforced #5 bars, 2 mats, 2 ways, 12” oc
Top mat, transverse: 3.14 x 5/8” x 12” x 12”/12" oc ÷ 144 in2 = 0.16
Top mat, longitudinal = 0.16
Bottom mat, transverse = 0.16
Bottom mat, longitudinal = 0.16
Total = 0.65
Sample Calculation #3
Lightly Reinforced: #4 Bars, 1 mat, 2 ways, 16” oc
Transverse = 3.14 x 4/8” x 12” x 12”/16" oc ÷ 144 in2 = 0.1
Longitudinal: 0.1
Total: 0.2
