Reinforced concrete structures provide a highly alkaline and protective environment for steel bar reinforcements. The protective environment is destroyed upon the introduction of chloride ions, allowing for corrosion if moisture and oxygen are present. Microwave nondestructive testing is one method to detect chloride in cement‐based materials. A comprehensive understanding of how chlorides are deposited in mortar that is exposed to cyclical salt water soaking and oven drying is desired. Modeling is a necessary component of this process. This paper presents the modeling process using mixing models and possible salt distributions in conjunction with a multi‐layer code that provides simulated results. © 2003 American Institute of Physics