Air entrainment 4

[lsmfse]

We have a project where the specifications call for 4%-5% air entrainment for an underground concrete water tank. Testing during the pour showed air content greater than 12% for some of the batches. The site isn't subject to freeze/thaw. Based on my research, other than the concrete looses about 5% of strength per 1% of air, what other issues might be of concern?

 

[beton1]

So it sounds as if this episode is ending positively? Maybe there were some testing problems since the cored samples came up with a much higher f'c and permeability is low. Also, your design works with a lower f'c. A good end to the year?!

 

[MultiVar]

All's well that core-tests well. Happy New Year... hope you get paid on time. ;')

Seems commons sense that test cylinders should be cured exactly as the pour is, yes/no? But I've been on sites where the test tech is putting the samples away in the construction trailer, or the crew cab of his truck, etc... WTH?

 

[Ron]

MultiVar....NO NO NO!! The cylinders should be cured under standard conditions, not field conditions. The cylinders are to check the mix design, not the in place concrete.

 

[conceng]

Ron is right...the cylinders are to measure the quality of the concrete DELIVERED. By exposing cylinders to the same variables as the in place concrete, the conditions could influence the stengths of the cylinders such that you wouldn't know what you've got. It's also important to point out that the cylinders are much more sensitive to environmental variables due to their relatively small size and thermal mass.

Greg