concrete deterioration
concrete deterioration
(OP)
The bottom of a cast in place grandstand is deteriorating. The paint is delaminating in several spots because the concrete is extremely soft and crumbling. Not sure if deicing chemicals were ever used on the top surface, which is also painted and looks sound. Anyone have any ideas for the cause and how to investigate? Location is the Southeast - age is approximately 50 years. I haven't determined yet the depth of the softness - looks like it is at least 1" to 2". I will suggest removing unsound material and repairing with a repair product, but I would like to know why it it doing this if it is possible to find out.






RE: concrete deterioration
Is is just the deterioration of concrete and delamination of the paint? Are there any deeper issues such as spalling due to corrsion of reinforcing steel. You will need to consider doing a condition study to see what is really going on.
RE: concrete deterioration
RE: concrete deterioration
There are also some insitu compression tests that can be done to estimate residual strength.
I would recommend propping it up before carrying out any works.
RE: concrete deterioration
Some things that might be considered:
Verifying that the reinforcement hasn't lost significant area due to rusting (cleaning off rebar and measuring diameter of "good" steel).
Testing concrete for chloride content (if there is high chlorides you should consider adding zinc sacrificial anodes to the repair).
Removing old "soft" concrete and replacing with patching compounds or with just concrete or with shotcrete repair methods (remove concrete to at least 3/4" around reinforcement to ensure good bond.)
RE: concrete deterioration
The only way to test for it that I am aware of is to have it examined under a micro scope.
If this is the case, simply covering it will not solve your problem.
A call to the state DOT may reveal if reative aggregates are present in the local area.
RE: concrete deterioration
What you've described sounds like advanced carbonation and efflorescence.
Removing 2" of concrete will likely get you to the rebar level. If that's the case, you'll need to consider some supplemental reinforcement, pinning, or carbon fiber overlay.
Get the petrography done. It should tell you a lot. If you are in the Atlanta area, there are several firms in the area that can do petrography.