The deterioration process of limestone in the Anahita Temple of Kangavar (West Iran)

Abstract

The well-known archaeological site of Anahita Temple at Kangavar is one of the most important Iranian stone monuments. It has been dated by various authors in an interval extended from Achaemenid to Sasanian Persian Empires (sixth century BCE to seventh century AD). Significant weathering has been occurred in various stone blocks used in the construction of this monument. The aim of this research is to study the deterioration process of the stone blocks used in the Temple. It includes chemical and mineralogical analysis of stones, characterization of deterioration patterns and processes, and identification of factors influenced the process. Results have been obtained by on-site and laboratory studies, including optical microscopy, petrography, X-ray fluorescence, X-ray diffraction and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy methods. They showed that low-porosity limestone and dolomitic limestone have been used in the construction of the Temple, which have a compact micritic structure with variable size calcite veins (sparite) and clay veins. According to the on-site and laboratory studies, the deterioration patterns are partially similar in majority of the stone blocks and include different types of detachments as well as biological colonisations. The multianalytical results proved that the deterioration process is mainly of physical weathering type, due to structural and chemical characteristics of the limestone as well as climate factors, temperature fluctuations in particular. It turned out that limestone characteristics (including presence of clay veins as well as heterogeneity of calcitic matrix (micrite and sparite)) can affect the behaviour of stone blocks against climate factors; helping us to find reasons behind physical weathering of limestone in the cultural/historical sites and monuments.

Diagnosis, Photogrammetry and Conservation Treatment with Nanomaterials of Sacidava Fortress

“…Similar results have been reported in the literature [19,20]. XRD technique (Figure 4) correlated with XRF analysis of mortars identified several crystalline phases: quartz (SiO 2-28 (2q)) and calcite/dolomite (carbonate Ca and Mg-30, 38(2q)), small amounts of feldspaths (cations containing alkali metal aluminosilicate and alkaline earth metals), as well as mica and berlinite [18].…”

Petrophysical properties of limestones: influence on behaviour under different environmental conditions and applications

“…Textural and porous properties are the main factors ruling the stone behaviour, but weather conditions will enhance the degradation of the high porous materials. Barnoos et al (2020) mention the presence of secondary calcite veins and clay veins in the microstructure of a limestone as cause for delamination and fragmentation and washing out during exposure to water, respectively. Yagiz (2011) identi ed random microcracks in lled with calcite, which turns the rock weaker than anticipated.…”

“…The knowledge of the PMP of stones used in heritage monuments is a critical issue, both to know the constraint factors dominating the evolution under speci c environmental conditions and predict the durability and span of life of the buildings, and to choose the best solution when repairing works are necessary. The identi cation of the PMP of building stones can lead to their better maintenance and safekeeping (Taghipour et al 2016; Korkanç et al 2021), avoiding the use of inappropriate restoration material (Barnoos et al 2020). When repairing or replacement of damaged stones is necessary, the best option is to use stones with similar properties from the original ancient quarries (Taghipour et al 2016).…”

Petrophysical Properties of Limestones - Influence On Behaviour Under Different Environmental Conditions And Applications

“…Further studies are necessary to assess if clay swelling minerals are present in the micrite groundmass around or in the stylolitic planes. As mentioned above a small clay content can have a deep impact on stone expansion(Berthonneau et al 2016;Nasri et al 2019;Barnoos et al 2020).…”

“…Usually, limestones show low hydric dilatation because these rocks have low clay content(Siegesmund and Dürrast, 2014). The presence of swelling clay is the cause for the dilation behaviour of natural stones and contributes to degradation(Wedekind et al 2013;Cherblanc et al 2016;Nasri et al 2019;Barnoos et al 2020) Berthonneau et al (2016). mention the effect of a low clay content (< 1.3%) in the macroscopic physical process of the hydric dilation Aly et al (2018).…”