ALBERT

Description: Salt absorption in porous building stones contributes greatly to the degradation of monuments. Two French porous limestones with similar main characteristics (total porosity, densities and mechanical resistance) were studied: white Tuffeau and Sebastopol stone. Accelerated ageing (weathering) tests were carried out by applying immersion-drying cycles with water containing sodium sulphate or sodium chloride. Samples of the two stones were tested separately and then in sets containing both rock varieties. The results facilitated interpretation of the observed and measured responses of these two limestones to the cycling salt crystallization. The durability of studied stones was evaluated by determining the normalized weight changes during the applied cycles. The Sebastopol stone amplified the amount of salt stored in the Tuffeau with increasing number of cycles performed, inducing its more rapid degradation. Water retention and water transfer in the pore space were found to be two main factors controlling the rate and the type of stone decay due to the salt crystallization.

Description: We used teleseismic P-wave receiver functions recorded by the Eastern Turkey Seismic Experiment to determine the crustal structure across an active continent-continent collision zone. Moho depth and Vp/Vs variations in the region are mapped by incorporating crustal multiples and later two-dimsional (2-D) seismic profiles are produced using a common conversion point technique with our crustal Vp/Vs estimates. Moho depths do not correlate with surface topography and reveal a relatively thin crust consistent with the high plateau being supported by hot asthenosphere near the base of the crust. Under the Arabian plate, the crust is thinnest (c. 35 km) and exhibits high Vp/Vs ([≥]1.8) associated with mafic compositions. In the east, the crust gradually becomes thicker towards the north and exceeds 45 km in the northeastern side whereas in the west, the crust thickens sharply near the Bitlis suture and displays pronounced Moho topography within the Anatolian plate that suggests the presence of multiple fragments. Vp/Vs variations show an anomalously high Vp/Vs corridor ([≥]1.85) along the North Anatolian Fault and near the youngest volcanic units (c. 3 Ma) and support the presence of partial melt. This corridor is spatially limited from both north and south by low Vp/Vs regions implying a change in crustal composition. Near the Bitlis suture, a layered Vp/Vs model points to the source of low Vp/Vs in the lower crust that may be rich in quartz. Furthermore, the seismic profiles indicate a prominent low velocity zone in the lower crust across a large area beneath the plateau that may act as a decoupling zone between the crust and upper mantle.

Description: 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.

Description: Preservation of cultural heritage, especially historic monuments, is a vital task. In addition, waste recovery is an essential goal of sustainable development. In this study the properties of a food waste, eggshells, and a quarry waste, powder obtained from stone-extraction operations, are evaluated in terms of their possible use in restoration mortar. An excellent lime has been developed based on eggshell calcination. A lime-based mortar exclusively composed of this eggshell lime and tuffeau powder was developed and characterized in order to demonstrate its compatibility with restoration works. To pursue this objective, microstructural, physical and mechanical properties were investigated and compared to those of the tuffeau limestone. The tested formulation using tuffeau powder was found to meet compatibility requirements up until the hygrometric environment lowered the water content of the mortar. The desiccation of the mortar can then generate shrinkage cracks leading to mortar crumbling. As a consequence, hygrometric susceptibility of the mortar is an essential parameter to be investigated in order to study the durability of lime-based mortars made out of limestone powder.