Experimental measurement of disjoining force at the glass–salt interface: A direct evidence of salt degradation potential caused by crystallization pressure

Abstract Salt degradation is a well-known but still poorly understood problem. Determination of crystallization pressure that growing crystals exert on the pore walls represents a challenge solved by authors from different points of view. Nevertheless, few papers are aimed at the experimental measurement of the crystallization pressure magnitude. A novel high precision device able to detect repulsive forces generated by a crystal at the crystal/glass interface has been designed. Although some problems with determining the correct contact area of the confined crystal surface, which is most probably not atomically smooth, still exist, the results are comparable to data from other experimental studies. Crystallization experiments were performed with sodium chloride under 30 ± 2% and 60 ± 2% relative humidity (RH) conditions and with sodium sulfate in 30 ± 2% RH. The disjoining pressure values were variable but did not exceed 1 MPa. Special interest was aimed at determination of disjoining pressure of sodium sulfate during phase transition after wetting, since this phenomenon creates most damage during standard crystallization tests. The disjoining pressure values were between 0.957 and 3.159 MPa – sufficiently high to overcome the tensile strength of most of the porous building materials.