Q. We're building a concrete swimming pool in a rural area. For any placement using more than 5 cubic yards of concrete, the specifications require cylinders to be molded and tested for compressive strength. The closest testing lab is 100 miles away, so getting the cylinders to the lab is going to be expensive. Is there any way to avoid having to test the concrete?
A. How many cubic yards are you using? Section 188.8.131.52.c of ACI 301-96, "Standard Specifications for Structural Concrete," allows strength tests to be waived by the architect/engineer if, in his judgment, adequate evidence of satisfactory strength is provided and when the total quantity of concrete with a given mix design is less than 50 cubic yards.
If your concrete supplier has records showing the average strength for the concrete being supplied, and batch tickets can demonstrate that the design water-cement ratio hasn't been exceeded by jobsite-added water, the specifier may dispense with the requirement for strength tests.