Non-destructive methods for determining weathering in historical monuments: a case study from Merv City, Turkmenistan

Any changes or restorations to archaeological sites or historical buildings that are protected by law are prohibited without permission. In order to preserve the architectural heritage of a structure or a residential area that has retained its original character as a historical legacy, it is important to identify the weathering of used structural material or deterioration of strength, which can occur due to environmental conditions, or damage caused by natural or artificial factors over time. It is desirable, however, to avoid applications that will cause permanent damage in the structures, such as core sampling or stripping, when such studies are made. Non-destructive methods can eliminate this problem, but must be investigated to show their applicability. In this study, ultrasonic velocity and crack depth compressive strength determinations are applied to assess the integrity of brick structures in Merv, an ancient city of Turkmenistan. Two towers and two mausoleums are investigated, where Hakem El Gifari and Bureyde el-Eslemi are lying. The structural integrity of the towers and mausoleums are classified as weak and poor, respectively, according to classifications of the International Atomic Energy Agency. Crack depth classification infer class II and III for the structures, and the compressive strengths show a variation between 2-8 MPa in towers and 20 MPa in mausoleums. This variation in brick performance can be attributed to winds that blow from NW direction and the differences in the workmanship in the restoration over the buildings’ history. When restoration shall be conducted according to the results obtained, both historical heritage can be better preserved and any budget for structural reinforcement could be reduced