Multi-scale analysis on the influence of moisture on the mechanical behavior of ferruginous sandstone

Moisture is known to decrease the mechanical properties of brittle construction materials. The present study focuses on the influence of moisture on the mechanical behavior of ferruginous sandstone in order to understand and quantify this effect. The investigated Diestian and Brusselian ferruginous sandstone have frequently been applied in monumental constructions and many of these monuments presently suffer from material degradation and, in some cases, stability concerns. Experimental analysis is performed on different levels, from micro to macro behavior, in order to obtain a more detailed picture of the acting processes. Therefore, a methodology is proposed which combines established as well as advanced experimental techniques, involving non-destructive testing for pre-classification of the sandstone's quality, mineralogical analysis and investigation of mechanical properties under dry and saturated conditions. It was observed that the decrease of mechanical properties, such as strength and stiffness, is more pronounced for lower-quality ferruginous sandstone. It was also found that water adsorption by the sandstone during acoustic emission-controlled creep tests shifts the specimen's behavior from meta-stable creep damage to accelerated failure. These observations were linked to the results of the mineralogical study, in which the consolidation degree and clay content were analyzed and to the results of the microfocus computed tomography which visualized the fracture progress on a micro scale.