The influence of stone joints width and roughness on the efficiency of biocementation sealing

Biocementation is being used to seal cracks in stone and concrete for retrofitting and consolidation works, as alternative to conventional solutions such as using polymeric mortar. As when such traditional techniques are used, joint thickness and roughness play an important role on sealing efficiency and this must be investigated when using biocement. The efficiency of biocementation to seal joints in stone samples considering simultaneously their width and roughness is discussed in this paper. Joints with 0.4, 0.7 and 1 mm width, having smooth and rough surfaces, were artificially created on basalt stone disks. The joints were treated by biocementation until become sealed, i.e., until fluid stop flowing through the joint. Adhesion achieved with the treatment was evaluated by tensile strength measurements in Brazilian splitting tests, in which the samples were split by the sealed joint. The joint surfaces separated after the splitting test were analysed by digital analysis of photographs and stereomicroscope images to check the presence and homogeneity of the precipitated biocement. The tensile strength was larger for the artificial joints with larger width and rough surfaces (maximum values found are 3.94 and 5.67 MPa for the smooth and rough surfaces, respectively). The values found were half the values measured for the intact rock (8 MPa), but still in the order of magnitude of Mega Pascal, therefore indicating strong adhesion between the stone and biocement. Biocementation treatment therefore appears to be adequate for sealing stone joints with different widths within the range investigated and variable roughness.