Precast concrete that is generally blemish free raises the stakes considerably when it comes to delivering a top class repair. The same could be said for self compacting in situ concrete.
Whilst as with any remedial work the key starting point is flush, true and texture appropriate filling, colour matching such good original work up’s the anti to dizzy heights. Achieving a close colour match in terms of tone is not an issue per se. It is the successful diffusing of minute tonal variation to convince the eye to believe.
If the concrete is pre cast or site batched in steel shuttering then this adds a significant advantage as the surface quality of steel formed concrete tends to have a nice balance of light reflectivity. Not too shiny and not too dull.
The images here are the before and after of construction damage on a pre cast column for BP. It is irrelevant to the repair process but it is probably a PFA blended mix. The blotchy marks have come from differential curing not the casting p...