The concrete testing frequency has varied over the years. For many years, the concrete testing frequency was typically every 50 yards. This typical testing frequency has changed and has a greater variance from project to project. Ultimately the testing frequency is up to the approved project specifications and documents. However, there are building code requirements that have be developed as a minimum base line to use as a reference. Often engineers will reference these building codes or specifications in the project specifications.
According to ACI 318 Section 5.6 (Building Code Requirements for Structural Concrete), the following testing frequency should be performed:
- Samples for strength tests of each class of concrete placed each day shall be taken not less than once a day, nor less than once for each 150 cubic yards of concrete, nor less than once for each 5000 square feet of surface area for slabs and walls
- On a given project, if total volume of concrete is such that frequency of testing required by 5.6.1.1 would provide less than five strength tests for a given class of concrete, tests shall be made from at least five randomly selected batches or from each batch if fewer than five batches are used.
- When the total quantity of a given class of concrete is less than 50 cubic yards, strength test are not required when evidence of satisfactory strength is submitted to and approved by the building official.
According to ACI 301 (Specifications for Structural Concrete), The following testing frequency should be performed:
- Obtain at least one composite sample for each 100 cubic yards, or fraction thereof, of each concrete concrete mixture placed in any one day.
- When the total quantity of a given concrete mixture is less than 50 cubic yards, the strength tests may be waived by the Architect/Engineer.
Typically, the concrete is tested no less than every 100 cubic yards. The Department of Transportation and other miscellaneous projects , in some cases, will increase the testing test frequency past 100 cubic yard. To be safe, the project specifications should be reviewed prior to the start of concrete placement to determine the testing frequency.
