Influence of Clay Minerals Nature on the Hydromechanical and Fracture Behaviour of Stones

Overview & Synopsis

Elastic properties and fracture behaviour evolutions of two sedimentary stones are under study to estimate their influence on scaling effect of monumental stone heritage. Young moduli and toughness of Villarlod molasse and Thüringer sandstone are measured under moisture content variations with respect to their natural anisotropy. Several relative humidity levels are considered to investigate their effect upon humidification and drying. The stone property evolution is in close correlation with the identified clay phases of the matrix. It appears that clay minerals as smectite and glauconite influence the stone properties at very low moisture contents, whereas less swelling clays have impact only when high moisture contents are reached. This is in close correlation with the inherent deformation ability of these minerals. It is observed that nature and distribution of clay phases largely influence on the macroscopic behaviour under natural exposure conditions, as they modify the stone properties and represent the weakness planes of the stone.