Flexural Concrete Strength Test

[asv]

If the specification required for concrete is 525psi @ 28days and the result of the test is 375 @ 31days, shall it be considered for demolition? Any recommendations from experts out there, please?

 

[UltimateVelocity]

Most concrete strengths are designed stronger than working strength, this allows for just such an occasion. First, the engineer who designed the structure should do a recalculation to determine the actual strength needed for the structure. If the 28 day strengths still fall short it may be necessary to demolish. But first, drill a core sample from the structure to determine its actual strength. If after these steps, the structure fails to meet the strengths necessary, it will be necessary and safer to demolish.

 

As a mater of interest what was the nature of the structure you were supporting or constructing

 

[GThomas1]

I'm assuming here that you mean that the concrete tested at 3,750 and was specified at 5,250; which means that the concrete sample only tested at 71% of designed strength. Hopefully a hold cylander was made. That is an extra cylander which may be cured for 56 days, or if time does not permit, at an earlier time in order to confirm the 28 day break. If no hold cylander was made, I'm afraid that the test sample is just as suspect as the concrete on site. In these cases the structural engineer will definately recalculate to find if it is safe to remain in place. Also he will want to determine the strength of the actual concrete in place to find if the sample was made, cured and tested accurately. First choice is the Windsor Probe which is the least destructive test. If that is borderline, he will definately want to core the structure.