Climatic conditions and limestone decay in Al-Namrud monuments, Iraq: Review and discussion

The preservation of historic monuments needs understanding different parameters inducing the degradation of their construction materials. This study concerns the effect of climatic conditions on the degradation of an ancient historic site Al-Namrud-Iraq, about 3000 years old. These monuments constructed with a porous limestone are located in a rural area, about 30 km to the south east of Mosul city. In situ, observations show different types of stone decay such as sanding, spalling, granular disintegration, powdering, stone detachment and differential erosion. The present research assumes that the stone degradation is related to the long-term mechanical behavior under cyclic environmental conditions. Temperature and relative humidity will be taken into consideration after analyzing the Mosul meteorological data for two periods 1963-1965 and 1969-1970. The estimation of weathering of Al-Namrud monuments due to climatic conditions is analyzed through the effect of thermal stress, condensation and freezing-thawing action on the stone. Since the effects of condensation and freezing are limited, the major source of damage is supposed to be related to thermal stress, that increases if the daily stone temperature variation increases.