Interpretation for the bound water content of sludges measured via a dilatometric test is given in this paper. Thermodynamic analysis was conducted on the basis of the hypothesis that there exists a ''binding strength'' between the solid phase and the bound water which reduces the free energy of moisture artificially. To choose a freezing temperature is thereby equivalent to choose a threshold binding strength dividing the bound/non-bound water in a sludge. The portion of bound water thus identified is close to the physically absorbed moisture. A continuous moisture distribution is constructed. Copyright (C) 1996 Elsevier Science Ltd