Concrete Discoloration
Concrete Discoloration
(OP)
I have a project where we poured this architecturally exposed concrete wall. The contractor took 2 days to pull forms.
For some reason, the forms taken off during the 2nd day have left the concrete a unique "darker" color.
Everything, except the form removal, is identical. Same truck, same mix, same forms.
The wall points North.
The south side, curiously, is perfect. No checker board discoloration.
The concrete is about at day 15 in terms of curing process.
The owner is flipping out. No one knows what is going on. The end goal, is that all the concrete needs to match (same color).
Has anyone ever seen this?
PHOTO IS ATTACHED.
For some reason, the forms taken off during the 2nd day have left the concrete a unique "darker" color.
Everything, except the form removal, is identical. Same truck, same mix, same forms.
The wall points North.
The south side, curiously, is perfect. No checker board discoloration.
The concrete is about at day 15 in terms of curing process.
The owner is flipping out. No one knows what is going on. The end goal, is that all the concrete needs to match (same color).
Has anyone ever seen this?
PHOTO IS ATTACHED.






RE: Concrete Discoloration
RE: Concrete Discoloration
As far as seeing different color between form panel removal times; not really. I've seen concrete hold water in the pores and evaporate between form removal giving the appearance of different colors but after drying it goes away.
Only thing I can think of is some sort of reaction between something on the forms? Is it just surface deep? What color is the concrete when you grind away the surface with a rubbing brick?
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Concrete Discoloration
Sell the "feature" route and continue the pattern on up hahah.
RE: Concrete Discoloration
At first glance, everyone was like "let it dry". Now everyone is getting worried.
RE: Concrete Discoloration
The only thing that discounts a form flaw (something reacting) is that the only ones it happened on where the forms that were left on until the 2nd day.
RE: Concrete Discoloration
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Concrete Discoloration
That said, I think your odds of a uniform color improve if all of the formwork is removed at the same time, and all panels have been given the same time, temperature, wind, and humidity to cure. If the client (and the contract) demand a uniform look, I might give it a few more weeks and then consider some sort of abrasive removal of the skin surface (sand or water blasting??) It might fix the problem if the discoloration is mostly at the surface. Of course then the owner would have to live with a different surface profile (i.e. not a smooth finish).....pick your poison.
RE: Concrete Discoloration
Also surprising is that they didn't start top down with the removal.
RE: Concrete Discoloration
Regarding pulling all the forms, I'm not clear on why they didn't pull them all down, and how in the world they removed the bottom forms first.
RE: Concrete Discoloration
(Random side note; I once did a reasonably complex pipe routing 20 ft overhead using nothing but a portable self-leveling laser, a crayon to mark the floor slab, a magnetic tape, and a camera with a good zoom. 3D modeled all the existing pipes, cable trays, conduits, and what not. Didn't have any field install issues that I heard of.)
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Concrete Discoloration
RE: Concrete Discoloration
More hydration = darker color of grey.
RE: Concrete Discoloration
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com