Why test concrete?
Concrete is tested to ensure that the material that was specified and bought is the same material delivered to the job site. There are a dozen different test methods for freshly mixed concrete and at least another dozen tests for hardened concrete, not including test methods unique to organizations like the Army Corps of Engineers, the Federal Highway Administration, and state departments of transportation.
Question and answer courtesy of Portland Cement Association (PCA). More information is available at: http://www.cement.org/tech/cct_faqs.asp.