Testing of salt-contaminated materials:: use of aqueous solutions for control of relative humidity

Today, many kinds of laboratory tests are performed on salt-contaminated materials. In these tests the relative humidity is often controlled inside closed containers by means of selected salt solutions or pure water. This paper discusses the influence of the contaminant salts on the environmental conditions inside such containers. Two experiments were performed by monitoring the relative humidity and temperature when NaCl samples were kept over pure water. The results showed that the NaCl samples significantly disturbed the environmental conditions inside the containers. This indicates that methods of generating constant relative humidity by means of salt solutions or pure water can be inappropriate in the case of salt-contaminated materials. As a precautionary measure, monitoring of the environmental parameters inside the containers should be carried out.