Frozen concrete cylinder
Frozen concrete cylinder
(OP)
I had a test report from testing company, which show lower strength of cylinder at seven days and more than specified strength at 28 days. The reason specified by testing company for lower strength at 7 days was frozen cylinder during initial curing. Is it possible for concrete to gain strength at 28 days if it frozen during initial curing?
I also checked actual concrete at poured location, there was no signs of frost on the surface.
I also checked actual concrete at poured location, there was no signs of frost on the surface.






RE: Frozen concrete cylinder
Are you sure this wasn't a field-cure? Either way, more important that the actual placement was not allowed to freeze. You should ensure proper cold-weather concreting practices are utilized by the contractor.
If the concrete does freeze prior to reaching 1000psi, it probably would not have gained specified strength. If you got your strength it's probably okay.
Low temperatures obviously result in slower curing. Cold weather concreting with moderate to high fly-ash contents can result in some really low 7-day breaks, but normal performance at 28 days.
RE: Frozen concrete cylinder
If there was no evidence of freezing at the site, then the cylinders probably didn't freeze either.
RE: Frozen concrete cylinder
Dik
RE: Frozen concrete cylinder
How many cylinders in the batch? - Individual or averages?
In many modern labs the cut-off on the testing machine for routine testing cuts off as soon as there is a yield, but the cylinder can increase in strength.
Were the samples taken by the testing lab and curing controlled by the lab?
Who transported the cylinders from the site to the lab? - Important because 7 day cylinders are especially fragile and if they are not strapped to a pallet and/or cushioned a bump could show and early failure that is not representative of the in-place concrete strength.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Frozen concrete cylinder
Many testing labs are very good at what they do. They are careful not to compromise data in any way. Over the years, profit has become more difficult to achieve and training has suffered. This is certainly true of engineering technicians who do sampling and testing.
A universal testing machine, particularly with a high capacity range, is very expensive. As CM noted, many technicians are taught to drop the load before breaking the cylinder all the way down....this can lead to erroneously low results. It does prolong the life of the machine, but it does not follow the testing protocol they say they are following. Not good!
To evaluate this discrepance properly, you must go back over each step of the batching, delivery, placement, sampling, transport, testing, review and reporting of the data.
RE: Frozen concrete cylinder
RE: Frozen concrete cylinder
Specimens in the field are cured and tested in the lab under STANDARDIZED conditions to check the mix design...not the concrete in the structure. One reason standardized procedures are used is to have repeatable results from person to person and lab to lab (within the criteria of within-test and within-lab variations).
RE: Frozen concrete cylinder
RE: Frozen concrete cylinder