Experimental study on conservation and preservation for historical architecture using plaster finishing material

Abstract

Historical architectures and buildings have been built in Japan, often using plaster and mortar for surface finishing materials on the walls and ceilings regardless of structural types of masonry, wood and concrete. These plaster finishing materials are called Shikkui in Japanese, and the chemical ingredient is almost entirely Ca(OH)2. It resembles cement mortar and it becomes carbonized on the surface area during long term use. For example, the Himeji castle and the Gunkan Island (Battleship Island) of world heritage in Japan have used plaster materials as interior or exterior. Some of these historical architectures and buildings have been placed in harsh environment and occurred natural disaster frequently. Some historical architectures and buildings were damaged by the Great East Japan Earthquake 2011. There were some accidents caused by falling the ceiling, with dismal consequences for the buildings,and moreover lost the value of the building including the historical and traditional properties. Therefore, this study focused on the fundamental properties of strength and durability of plaster finishing materials applied to the ceiling. In this experiment, we produced many types of plaster specimens to evaluate the relationship between mix proportions and fundamental properties. These mix proportions have different contents of water, plaster, sand and natural plant fiber, and we conducted these experimental evaluations in detail. As these results in this study, it has been found that the mechanical strength of ceilings were related between plaster density within fiber and carbonated conditions. In addition, it would be expected to increase the potential fundamental properties and protect of authenticity by optimizing the use ratio of plaster materials.