Research On Repairing Broken White Marble Stone By Microbially Induced Carbonate Precipitation Techonology

The mechanic fracture of stone cultural relics will lead to the overall fracture and partial shedding of cultural relics.The paper applied microbially induced calcium carbonate precipitation(MICP)technology to repair broken white marble beams and weathered stone components of different sizes by injection grouting or gravity driven infiltration.The repair quality of stone beams was evaluated by X-ray CT scanning technology,bending test and ultrasonic testing technology and the factors affecting the repair quality were studied on the scale of mortar materials and stone beams.This paper will provide a new choice for restoring the fractured stone relics.Firstly,this paper repaired broken stone beams(40?40?160mm)by injection grouting.The repaired crack surface matches the original stone to guarantee the overall aesthetics of white marble cultural relics.The average flexural strength is 3.68 MPa,which reaches 35% of the strength before repair.CT scan results show that the density of the bonding layer increases with the repair process and the presence of water channels or connected pores in the bonding layer are important factors in influencing the flexural strength.Then,this paper repaired broken stone beams(40?40?160mm)by gravity driven infiltration and studied the effect of the repair method and the roughness of the contact surface on the repair quality.The results show that the repair quality of grouting method is always higher than that of infiltration method,the repair quality is higher with rougher contact surface and the average flexural strength of restored stone beams is 4.21 MPa and 3.81 MPa,respectively.The four-point bending strength of the broken stone beams(100?100?400mm)repaired by the two methods is 0.67 and 0.57 MPa,respectively.One the one hand,the effects of restoration methods and nutrient concentration on the strength of microbial mortar were studied on the scale of mortar material.The results show that the UCS of grouting cemented sand column is 19.40 Pa,the maximum value is 36.66 MPa,and the optimum nutrient concentration is 1.0M.The strength of cemented sand column by infiltration method is lower than that by grouting method.The solidification quality of sand column treated by integral infiltration is poor near the int erface of each layer,while that of sand column treated by stratified infiltration is far from the entrance.On the other hand,the effects of restoration methods,nutrient concentration and calcium salt types on the quality of restoration were compared fr om the scale of stone beam members(40?40?160mm)The results show that the strength of grouting method is less affected by the concentration,and the optimum concentration of permeation method is 1.0M.Calcium chloride as calcium source of stone beam repair quality is higher than calcium acetate.In the test,the strength of stone beams after repair can reach 75% of that before repair at most.In addition,the two methods are also applied to the laboratory repair of weathered white marble components.The in filtration method has successfully repaired the components with irregular cross section,and the grouting method has failed because the grouting system is difficult to seal.Finally,the results of ultrasonic testing in the process of repairing stone beams show that the velocity of wave changes little in the grouting process,and has poor correlation with the quality of repairing,and is affected by the fixture and water content.The results of indoor surface crack repairing test by ultrasonic horizontal me asurement show that the wave velocity sucessfully reflects the quality of surface crack repairing.