AASHTO TP 55-98 (2005)

This method covers the procedures for determining acid-soluble chloride ions in concrete and concrete mix ingredients.

The age of concrete, mortar, or hydrated portland cement at the time of sampling will have an effect on the acid-soluble chloride ion content. Therefore, unless early age studies are desired, it is recommended that the material be well cured and at least 28 days of age before sampling.