The previously repaired concrete surface was damaged again after many years. Whether previously repaired areas should also be rediscovered, if they are visually undamaged?
When reinforcing the surface, previously repaired places should also be uncovered, because that's the only way to check, that no further damage has occurred under the filling mortar. Apart from that, the same set of materials should be used, to eliminate adhesion problems and the risk of cracking between old and new repairs.
At what width of cracks should they be filled??
Fill cracks with an opening width above 0,3 mm. It is especially recommended to fill the cracks with a mass pressed under pressure.
What resins should be used to fill cracks under pressure?
For filling cracks caused by external forces, np. cracks crossing the direction of stresses in prestressed concrete, epoxy resin should be used. For all other scratches, polyurethane resin can be used.
Please describe the course of works on pressure filling of Fig
Scratches are drilled obliquely from the side, the drilled hole must intersect the crack. The mutual distance between successive holes should be small enough, so that when the crack is filled with resin later, the entire crack is closed.
After drilling, holes and cracks should be cleaned, np. by blowing with compressed air. Injection nozzles are screwed into the drilled holes, then resin is injected under pressure into the hole and crack using an airless device, which should completely fill the void. Because these are cracks caused by forces, epoxy must be used.