Weathering effects in an urban environment: a case study of tuffeau, a French porous limestone

A case study is carried out on a highly porous limestone called tuffeau located in an urban environment. Weathering effects are characterized by several complementary techniques: mechanical resistance (compressive test), imbibition (capillarity test), mercury intrusion porosimetry, chemical analysis [inductively coupled plasma-optical emission spectrometer (ICP-OES)], scanning electron microscope (SEM) image analysis and X-ray diffraction (XRD). The results show the different composition of the deteriorated zone of the stone and mainly the presence of high gypsum content in the black crust surface. The analysis also shows that the natural penetration of water into this stone under environmental conditions (atmospheric precipitation, relative humidity and temperature) is limited to 20 mm. Moreover, the presence of gypsum is only detected in this limited zone, which demonstrates the depth of alteration in this stone. Finally, this study clearly highlights the important role of water movements in the deterioration of stone.