Effects of Microbiologically Induced Calcium Carbonate Precipitation (MICP) on Properties of Historic Brick and Mortar in the Historic Site

Abstract

Thai historical buildings are located in the open air without protection, which exposes them to deterioration of the constructed materials and eventually results to the structural instability. This study explores the improvement of the materials of ancient buildings (consisting of bricks and mortars) by the Microbiologically Induced Calcium Carbonate Precipitation (MICP) method to fill in the hair cracks and voids on the material surface. Better engineering properties are thus expected. This method of improvement complies with the requirements of the Fine Arts Department that does not allow vibration around the area of ​​the historical site. The bacteria used in this study was Lysinibacillus which is a bacteria with high potential for calcium carbonate production. The bricks were adopted from factories in Ayutthaya and mortars mix were recommended by the Fine Arts Department. In the tests, both bricks and mortar were submerged in solution of Lysinibacillus in the laboratory for 14, 21, 28 days. An analysis by SEM (Scanning Electron Microscope) revealed that cracks and voids in the ancient materials were filled and the porosity decreased. The compressive strength was also increased.