Strain Gage Installation on Concrete Reinforcement

Surface Preparation

1. Degrease with a degreaser ( CSM-1A ) over at least a 6-in (152-mm) length of the bar at the proposed gage location.
    
2. Descale and smooth the rebar around its circumference with a grinder wheel. (Aluminum oxide or silicon carbide abrasive of approximately 50 mesh is preferred.) A 3-in (76-mm) length generally provides a sufficiently large descaled area for gage and protective coating installations. Surface finish after this operation should be about 180 microinches (5 micrometers) rms.
    
3. Wet abrade with Conditioner A and 220-grit silicon carbide wet-or-dry paper ( SCP-1 ). Use sufficient Conditioner A to prevent material from drying on the rebar surface before wiping dry.
    
4. Wipe dry with a clean gauze sponge ( GSP-1 ), then repeat Step 3 (with 320-grit paper ( SCP-2 )) and dry again.
    
5. Surface finish should be 63 to 125 microinch (1.6 to 3.2 mictometers) rms at the completion of the second wet-abrading operation.
    
6. Lay out the gage locations.
    
7. Scrub the installation area with fresh Conditioner A and a cotton applicator ( CSP-1 ). Wipe dry with gauze sponges ( GSP-1 ).
    
8. Scrub the area thoroughly with Neutralizer 5A and a cotton applicator and wipe dry with a gauze sponge as previously noted. This step must be accomplished thoroughly to neutralize all traces of Conditioner A used in Steps 3 through 7.
    
9. Mask an area with PCT-2A cellophane tape at the gage location to minimize flow-out of adhesive for subsequent protective coating application.

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