Oxygen and Concrete Curing 1

[hairman]

Is oxygen used in the curing of concrete? I'm looking for a cause of low oxygen levels in a new manhole. Oxygen was measured at 2% and CO2 8% in a manhole that was 3 weeks old.

 

[Ron]

Oxidation does occur during the curing process but not to extent of depletion of ambient oxygen supply. Assuming this is an active manhole, I would look to the influent/effluent as being a probable cause.

Considering the levels you have noted, I would also check the instrument to see if it is reading properly. Two percent oxygen is extremely low. Have you checked for volatiles (methane, etc.)?

 

[hairman]

The manhole in question was a sealed watervalve manhole, ie no effluent. The manhole was tested with three different monitors and the only gasses that were abnormal were O2 and CO2. Thanks for your input. Any other ideas?

 

[Ron]

The only thing I can think of is that since the manhole is sealed, there could have been negative pressure created either by wind blowing across the top or by some other means of evacuation. The concrete curing would not cause this condition.

 

[dicksewerrat]

You may want to look at the soils that the manhole is in. If it is high in organics, the O2 is being used by the rotting of the organics. Check all the manholes within a few thousand yards. Mark this manhole well as a hazardous area. We had a guy go down when in a manhole with low O2. It also was a water valve MH. I know I had to pull him out.