A transient technique for determining diffusion coefficients in hygroscopic materials

摘要

A transient technique is described to find the diffusion coeffients of moisture transfer in building materials as a function of moisture content. Measurements that take many months by steady-state methods can be done in days or even hours. The matrial is subjected to a staircase function of relative humidity steps, the transient weight changes noted, and a numerical algorithm used which extracts the Kirchhoff potential, one value for each relative humidity step and corresponding moisture content. Diffusion coefficients are then calculated from the Kirchhoff potential.