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what is "seriously fails"? and technically, nothing fails at 7 days however if the results are alarmingly low, it provides the team an opportunity to halt what they are doing and check to see where the problem might lie.
if you are the testing firm, check with the tech that made the cylinders to gather their thoughts. double check to see how the samples were made, transported, stored (includes initial storage by contractor), cured, etc. also check cylinders to see if something looks "strange" (slag, no paste, coke bottles, etc). and check delivery tickets since the wrong mix may have been sent or sat on site for 4 hours. if you are not testing, then check with the testing firm get info from them. other than that (assuming this is the first low break), wait to see what happens at 28 days or do preemptive coring. if your job has a break history and this is the first crazy low break, it may just be the anomoly that will occur from time to time. also, never rule out that the cylinders got disturbed by the contractor while they were curing onsite (even though the contractor is responsible for providing a water bath tank in a secure location).
if you are the testing firm, check with the tech that made the cylinders to gather their thoughts. double check to see how the samples were made, transported, stored (includes initial storage by contractor), cured, etc. also check cylinders to see if something looks "strange" (slag, no paste, coke bottles, etc). and check delivery tickets since the wrong mix may have been sent or sat on site for 4 hours. if you are not testing, then check with the testing firm get info from them. other than that (assuming this is the first low break), wait to see what happens at 28 days or do preemptive coring. if your job has a break history and this is the first crazy low break, it may just be the anomoly that will occur from time to time. also, never rule out that the cylinders got disturbed by the contractor while they were curing onsite (even though the contractor is responsible for providing a water bath tank in a secure location).
obtain the contractors test results (if he did any) and compare to yours?
Notify the contractor and owner immediately of your concern.
Ask them for a contingency plan to repair, replace or otherwise strengthen the structure if the concrete really does not meet spec.
Determine if the structure can still function adequately with some below strength concrete.
Plan to take cores from the structure to verify the cylinder results (either now or at 28-days).
But as stated, nothing has failed any test yet. The specs require 28-day strengths.
Notify the contractor and owner immediately of your concern.
Ask them for a contingency plan to repair, replace or otherwise strengthen the structure if the concrete really does not meet spec.
Determine if the structure can still function adequately with some below strength concrete.
Plan to take cores from the structure to verify the cylinder results (either now or at 28-days).
But as stated, nothing has failed any test yet. The specs require 28-day strengths.
Check the curing temperature as well. Low temperatures will slow the curing rate.
Another cause could be the use of PFA which slows the rate of cure down compared to OPC.
Stephen Argles
Land & Marine
Another cause could be the use of PFA which slows the rate of cure down compared to OPC.
Stephen Argles
Land & Marine
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