Study on Effectiveness of Three Materials Nano-SiO2, Nano-Ca(OH)2 and (NH4)2HPO4 as a Novel Superficial Consolidant on the limestone used in Pasargadae World Heritage Site

The materials that are now being used in the conservation of historic and cultural heritage are originally available in the market of industry. Recently, some of the materials are improved in the fields of conservation of heritage and they are so common in the consolidation of artificial objects or monuments. The aim of the study is identification of the proper material for consolidation of beige stone against environmental factors. Thus, three materials were chosen from the recent products which are more compatible with composition of limestone. Stone specimens were consolidated with Nano Estel (Nanostructure silicon dioxide SiO2 dispersion in water), Nano Lime (Ca(OH)2) (Nano-lime dispersion in isopropyl alcohol), and Dibasic ammonium phosphate ((NH4)2HPO4) well known as HAP method. Samples were characterized by FE-SEM and tested by Microdrilling resistance. The porosity also was analyzed by MIP. The results show Nano-lime has the lowest surface effectiveness which barely changed the physical properties of the stone in comparison with the others. In the case of covering, in both Estel and HAP, some microcracks (with branch and net pattern) were observed on the layer above substrate, in contrast, nano-lime made a homogeneous layer. Also, nano-lime treatment caused 6% reduction of the porosity which had the most effectiveness on stone porosity.