Let's assume the driveway mentioned earlier has exhibited a durability problem, such as surface scaling. Here are a few preliminary steps to take in examining a concrete defect before actually testing the hardened concrete.

Take a condition survey.Once all the project documents have been reviewed, the driveway slab should be visually surveyed and the conditions photographed to quantify the extent of the problem. The survey might include hammer tapping or chain dragging surfaces to detect unsound areas (ASTM D 4580, Standard Practice for Measuring Delaminations in Concrete Bridge Decks by Sounding). Plotting defects and other relevant characteristics such as cracks, popouts or scaling areas onto a sketch of the slab helps to assess the extent of defects and note patterns of interest.

Conduct sampling.Concrete sampling is conducted so that material properties can be evaluated to establish the cause(s) of deterioration. Consult a technician, construction professional or engineer experienced in troubleshooting concrete problems when considering sample numbers and locations. It's frequently beneficial to obtain samples from so called "good" vs. "bad" spots to isolate the cause of some defects. Some guidance on sampling is provided in ASTM C 823, Examination and Sampling of Hardened Concrete. Although multiple tests can be conducted on a single core sample, limiting samples to one core is not recommended since a single sample may skew the results if the sample is nonrepresentative. If you can't find a local coring company or testing lab to cut core samples, go to the Concrete Sawing and Drilling Association website (www.csda.org) to locate a member near the project who can then provide you with an estimate to conduct the sample removal. CSDA members are located across the country and are well trained and equipped to handle a wide array of concrete cutting needs.

Choose a testing laboratory.Concrete samples should be tested by a certified laboratory. Check with the laboratory on their experience dealing with the type of problem you are examining. Experience is a big plus, so you should select a particular testing lab based on experience and not just price alone.

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