Study On Surface Reinforcement Of Calcareous Cultural Relics Based On Calcium Oxide

The limestone cultural relics are confronted with the serious weathering problems corresponding to the natural and contrived factors. The main forms were salting-out, exfoliation and crack extension, etc. Therefore, the seven Qing dynasty steles were investigated for evaluating their current preservation situation, infrared spectroscopy (IR), X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), Environmental scanning electron microscopy (ESEM) were applied to reveal the corrosion mechanism, which will provide important reference data to select proper protective methods.In this paper, the naturally occurring calcium-based biofilms on the surface of some monuments inspired us to use a novel calcium source—calcium alkoxides as the precursor to prepare the consolidated protective layers as calcium carbonate through biomimetic synthesis method.The following works have been accomplished by experiments:(1) Calcium-methoxide was prepared by direct reaction between metal calcium and anhydrous methanol, the mineralization mechanism of calcium alkoxides was discussed after its mineralization process was studied in atmospheric environment;(2) Calcium carbonate and calcium oxalate layers were synthesized by calcium alkoxides. The results indicate that calcium methoxide can slowly translate into calcium carbonate in the suitable humidity and carbon dioxide concentration;(3) Ca(OCH3)2 and soluble poly(acrylic acid) additive(PAA) were prepared as the calcium precursor solution which will formed a homogeneous CaCO3 biofilm above the chitosan matrix;(4) The porous simulated limestone samples were prepared after the aging test. The calcium carbonate particles would form after coating the calcium methoxide solution on its surface which could fill the holes of the surface layer. Meantime, a series of calcium carbonate, calcium oxalate and apatite inorganic protective layers were synthesized on the surface of the simulated limestone samples which enhance the strength of surface.The weathering degree of stone cultural relics should be evaluated first which benefit us to choose the different protective methods. The particle-filled consolidation layers are suitable to the porous surface under a serious weathering condition, while the calcium-base inorganic biofilm is used to protect the stone with a smooth surface under low degree of weathering. Moreover, when the protective layers disappear, they can be recoated on the stone surface.