Originally Posted By: mkober
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As mentioned by others, epoxy injection is frequently used as a repair medium for cracks in concrete. It can be used for both structural repairs and cosmetic repairs. The surface epoxy visible is actually an epoxy sealing gel, placed over the entire run of crack after the injection ports (usually flexible plastic tubes) are set, to prevent surface seepage of the injected, very low viscosity epoxy material. The nails are placed sequentially to plug the ports as the nozzle operator proceeds, usually from bottom to top along a vertical crack. This procedure is actually "old" technology, requiring the use of a vacuum-swivel chuck for drilling the injection port holes to avoid impacting the crack interior with drilling tailings--a far better technique involves simply placing temporary tape strips across the crack before applying sealing gel, then tearing off the tape and injecting epoxy using a rubber-tipped injection nozzle, followed by a quick swipe with a wax block to seal the opening. There are many things to look for in a repaired concrete member, but you don't necessarily have to defer to an engineer--an experienced concrete repair contractor, if available, could be just as enlightening if there is any doubt as to the effectiveness of the repair. The second picture looks like another vertical crack is present (to the left of the sealed crack), which would indicate that the wall is still subject to the forces that caused the initial cracking; this in itself would warrant further evaluation by a qualified engineer to determine exactly what is causing the wall to fail (i.e., missing or misplaced reinforcing steel, excessive lateral forces resulting from saturated backfill, weak concrete etc.). I've monitored many heavy civil concrete repair contracts working with a number of different epoxy injection contractors, and have observed properly-performed epoxy injection repairs far outnumber repairs that fail to perform satisfactorily.
Michael J. Kober, P.E. and H.I.
"NACHI Member and Proud Of It!"