Chloride and carbonation testing of concrete

Chloride profile testing

Powder samples drilled at increasing depths, or cores sliced in the lab, are tested for chloride content to ASTM C1152 (acid-soluble) or ASTM C1218 (water-soluble).

Plotting chloride against depth answers two questions. Where did the chlorides come from? A profile that is high at the surface and falls with depth points to salt from outside, while a roughly uniform profile suggests chlorides cast into the original concrete. And how close is the corrosion threshold to the steel?

Carbonation depth testing

A phenolphthalein indicator is sprayed on a freshly broken core or drilled surface. Uncarbonated concrete turns pink; carbonated concrete stays colorless. Comparing the carbonation depth with the concrete cover at the same spot shows whether the steel has lost its protection.

Carbonation matters most in older buildings, in sheltered areas such as garages and interior slabs, and wherever the cover is thin.

Why the results matter for repairs

A repair that removes only the cracked concrete can leave contaminated concrete around the steel and speed up corrosion next to the new patch. Chloride and carbonation results define:

• How much concrete must be removed around the bars
• Where galvanic anodes or cathodic protection are worth the cost
• How long a repair can be expected to last, which also feeds the remaining useful life in a SIRS

How samples are taken

Sample locations are chosen from the half-cell potential map so they represent both corroding and passive areas. Cores and drill holes are small and patched when we finish, and each result is tied to a location on your drawings.