Low Concrete Breaks

[mmpossum]

I have a question about some concrete breaks that we are getting on our site. We need to have a psi of 5000. Some are making this by 14 day breaks and some aren't. There is fly ash in the mix and I'm wondering how much gain I can see, if any due to the fly ash at a later date (28 day breaks)? There is about 143 lbs of fly ash per cy and about 469 lbs of cement. Not sure what other info is needed but I can supply more info.

Thanks

 

[Ron]

Post a copy of the mix design...that will help.

Variability in a fly ash mix is expected; however, achieving the design strength in 14 days is a bit unusual unless you have an overdesign condition that needs such.

Fly will cause a slower strength gain, typically on the order of a 20% reduction in early strength (at 7 days). The ultimate strength at 28 days is not greatly affected; however, the concrete will typically gain strength beyond the 28-day point.