The proof of concrete quality is field performance under actual loading and environmental conditions. But before concrete experiences much of this exposure, it's necessary to determine its acceptability and make projections about its long-term performance. These judgements are based, in part, on the results of tests performed on hardened concrete. Standardized tests are available for:
- Estimating mechanical properties, such as compressive, tensile, or flexural strength
- Estimating stiffness or elasticity
- Indicating concrete durability factors, such as permeability or resistance to freeze-thaw, scaling, and abrasion
When given the opportunity to select or specify tests of concrete, determine specifically what is the required performance. If general concrete quality or compressive strength is the only issue, specify the ASTM C 39 compression test. If your application is more sensitive to flexural cracking, them maybe the ASTM C 78 or C 293 beam tests are more appropriate. If durability is the key to the concrete's success, consider tests that measure permeability, absorption, and abrasion resistance. Don't rely on conventional wisdom that says if compressive strength is satisfactory everything else will be OK.