Geochemical characteristics of surface efflorescence on the seventh century stone pagoda in Republic of Korea

Abstract

This study presents detailed description and geochemical characteristics of the efflorescence caused by interaction of water and the concrete on the surface of the seventh granitic stone pagoda in Republic of Korea. The pagoda comprised light gray medium-grained biotite granite with partial porphyritic texture, and it has been repaired for the destroyed parts using concrete in the 1910s. The surface of the pagoda was found to be contaminated by efflorescence at present. As a result of the study, the efflorescence is more concentrated within the areas of water pathway and the northern faces, and in the time of winter season. The efflorescent pollutants were mainly composed of carbonates. Through the extraction experiment, inorganic components of the efflorescence were quantitatively analyzed and discussed for an application with regard to the surface cleaning. The cleaning solvent with pH 6.2 is more effective than pH 5.0 to remove the efflorescent pollutants in general, however, the pH 5.0 solvent showed better results only for anions. Cleaning using chemical agents should be conducted only for small spots with sufficient water washing. And the cleaning effectiveness shows the maximum with the duration of 1 h in which soluble elements dissolve in the solvent the most.