Refinement of categorization and scaling of weathering-related damage to natural stone: case study on oolitic limestone from El-Shatbi Tombs (Egypt)

Natural rocks, as well as artificial building materials, in coastal regions are subject to severe attack by salts, primarily from sea spray, acid rain and/or domestic water in industrial and highly populated cities. As the oolitic limestone is the main rock through which the Greco-Roman sites had been excavated, then, the main aims of the current study are to define the damage category (DC) for the weathered oolitic limestone bedrock at coastal regions, with the Greco-Roman El-Shatbi Tombs serving as a case study. Additionally, it aims to modify the DC scale of Fitzner and Heinrichs (The Karolinum Press, pp. 11-56, 2002) to be applicable for defining the damage categories for a given archaeological site where the existing scale isn't based on any numerical limitations to previously define the DC of a given archaeological site. Detailed field investigations including photo-documentation, measurement of the dimensions of these weathering forms and consideration of the wall side orientation to sea spray at El-Shatbi Tombs have been used in tandem with the modified damage category scale to assess the damage category at these tombs. The net result of processing the field data indicated very severe damage at this site. The laboratory analysis for the small rock samples collected at El-Shatbi Tombs indicated that salts act within the pores of this limestone, particularly in 0.01-0.1-mu m pores, at this semi-arid region.