matching appearance of existing and patched concrete

[samdamon]

Gents-

Have a client who wants to repair fifty year old exposed architectural concrete and have the new patching match the older existing material as closely in appearance as possible. The repairs required are typically patching of partial-depth spalls (due to poor cover on bars).

The old concrete is of course weathered and carries some dirt, and will need to be cleaned. Are there ways that new concrete or new vert/overhead repair mortars can be tinted or colored (but not painted) after or before placement? I have heard that a skilled mason can sometimes match old brick mortar, is it feasible to do the same thing in concrete with trial colored mixtures etc?

The texture of the new materials also has to be adjusted to match if possible.

This appears to be a very difficult and maybe impossible task and I wonder if anyone else has attempted it.

 

[dik]

Nearly impossible to do... you may want to contact a specialty firm similar to Nawkaw (sp?)...

Dik

 

[MiketheEngineer]

Lots of luck!!

Could you possibly "patch" the whole thing?? Probably out of the question....

 

[bridgebuster]

On an episode of "This Old House" or "Hometime" - I don't recall which - the crew repointed a portion of a wall by grinding up the old mortar and mixing it with the new mortar, in order to match the color.

Might be worth a try but I agree that be it will be difficult, particularly if it's a large area. You're right -it comes down to the mason's skill.

 

[SkiisAndBikes]

Ten or so years ago, I was on a similar project. We did some testing for colour using various mixes, including the addition of super white cement to some of the mixes. In the end, nothing really matched but we did get a bit closer. The opinion of the architect on the project was that A) over time the walls will get dirty and somewhat conceal the patches and B) the personnel involved in the project are very aware of the colour differences, however, the general public walking at ground level do not have the same awareness nor interest, thus it's less of a problem. In the end, we were solving a problem of falling concrete which was the priority.

The workers did conceal some epoxy lines with ground up stone dust, applied while the epoxy was still tacky. Again, it took many trials to get something close to blending.

Good luck.

 

[Prepakt1]

Had this problem with foundations of a very long 14th century bridge. We were instally scour mats around the bridge which would be exposed at low tide and they did not want to see new concrete. Took six months of samples before a colour was finally agreed.

Intrusion Prepakt /marineconcrete.com

 

[dicksewerrat]

Sometimes you can mix in a little carbon black to get an older greyer color. Also do the repair then sandblast the whole bldg. Do test patches ina hidden place.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com