A method of limiting or reducing permeability of a matrix to liquid or gas flow is described. The method includes limiting inflow of water and/or gas into passages such as cavities, fissures, voids and the like, encountered in formations such as geological formations. The method includes steps of measuring one or more parameters relating to the matrix and selecting one or more components of a multi-component sealing composition with reference to the measured parameters. The selected components are introduced into the passage where it is set or coagulated to form a seal. Method is also described whereby the passage is sealed with a sealing composition comprising a grout component and a grout curing agent. A portion of the grout component is mixed with a portion of grout curing agent, the ratio of each being selected with reference to the measured parameters. The combined grout/curing agent are introduced into the passage where rate of curing or setting is controlled by modifying the ratio.