Comparison of vulnerability conditions of adobes’ structure – the study of historical and restored adobes of Kooh-e Khajeh ancient site (Kohan Dezh castle) in Sistan, Iran

Abstract

Adobe constructions are very frequent in dry, hot and desert regions. Due to weather conditions and the availability of suitable resources and earth to make adobes, Kohan Dezh castle, at the foot of Kooh-e Khajeh hill (Sistan region) is among the first places where such constructions were made. Owing to the particular properties of the adobe, the constructions have always been vulnerable to weather conditions, especially moisture. Before restoring such monuments and altering their structure, sufficient research on their morphology and scientific-based restoration experiments need to be carried out ; the results are integrated in planning the restoration project and the related scientific research. In Kohan Dezh Castle Restoration Workshop Project, restoration adobes produced in a previous restoration project were compared to the original adobes in order to understand the differences in their structure and constituent components. In the next stage, results were used to carry out necessary experiments to examine the vulnerability conditions for each of these samples against moisture. Finally, the strengths and weaknesses of restoration adobes were also studied. The analyses included gradation of the soil comprising the adobes, determination of density and porosity percentage, capillary tension test, water immersion test, abrasion resistance test, compressive strength test, and artificial rain which proved that the adobes produced for restoration were more vulnerable to moisture-induced damage then the historical ones. In order to optimize the structure of restoration adobes and increase their resistance against moisture-induced damage, their structure and gradation of their compounds and particles were modified so as to resemble those of the historical ones.