ASTM C39 has remained the industry standard for testing the compressive strength of cylindrical concrete specimens for more than 80 years. Specimens sampled from fresh concrete are mold cured in a cylindrical fashion for intervals ranging from 24 hours to 90 days. Additionally, ASTM C39 covers drilled core samples which can be used to test the strength of a newly finished concrete structure or one that is showing signs of distress.
ASTM C39 requires the prepared concrete sample to be placed on the lower platen of a compression testing system and carefully aligned with the loading axis (centered between the platens). To ease the burden of handling heavy concrete specimens, we offer a loading device that helps to ensure operator safety and improve productivity. To meet the alignment requirements of the standard, we recommend using a combination of our standard platen (bottom) and spherically-seated compression platen (upper). Also, be aware of the concrete capping methods outlined in ASTM C39 as they play a critical role with respect to result integrity.
Once a technician begins a test, load should be applied without shock at a stress rate consistent with the standard. We suggest using the soft start feature in Partner™ Materials Testing Software to prevent shocking the specimen and to set the appropriate loading rate. Application of force should continue well past the point at which the ultimate load is achieved, and the specimen exhibits a well defined fracture pattern.
One of the benefits of our testing systems is that they can be used for a variety of construction related standards and materials. For instance our Industrial Series DX, HDX, KPX, and LX Model frames can be used to test ASTM C39 as well as rebar, fasteners and a variety of other concrete shapes. Additionally, we have RD and DX Model compression-only systems for customers with less diverse requirements.
We recommend reading and reviewing ASTM C39 in order to fully understand the test setup, procedures, and results requirements.