Grouting compositions have been used for many years to minimize movement of water or other fluids into, through and out of wells and other subsurface cavities. Grouts have also been used to limit the movement of water and other fluids into buried foundations and other subsurface structures. Grout compositions incorporating bentonite are known to exhibit the characteristic of low permeability to fluids. In these compositions the degree of impermeability is directly related to the amount of bentonite present. Prior to the development of this invention, high concentrations of bentonite in grout mixtures have made the mixtures rapidly become too thick, viscous and sticky to be useful. Such mixtures can quickly clog pumping equipment and related conveying hoses and pipes, making them unusable.
Mason, U.S. Pat. No. 4,463,808, describes a composition in which bentonite, especially granular bentonite, or other water swellable clay is added to a premixed water and polymer solution. The polymer is a water dispersable hydrolyzed polyacrylamide which inhibits the swelling of the clay for a sufficient period of time to allow the fluid grout thus produced to be placed at the desired location in the well borehole. Granular bentonite is stated to be particularly desirable for use in this composition because finely ground bentonite swells more rapidly and must be more rapidly emplaced in the well bore. The amount of bentonite indicated for this composition is from 2 to 4 pounds per gallon of water.
Harriett, U.S. Pat. Nos. 4,696,698 and 4,696,699, describes grouting compositions containing up to 80% bentonite or other water swellable clay, with up to 80% non-swelling particulate fillers such as fly ash, diatomaceous earth or calcined clays, up to 35% water soluble silicates as solidifiers, up to 35% gelling agents such as magnesium oxide or soda ash and up to 35% multivalent cation source. This composition optionally uses sodium pyrophosphate as a dispersing agent for the water swellable clay. Harriett cautions against the use of polymer treatment of the water swellable clay using salts of polyacrylic acid and other polymer agents in order to avoid premature gelling of the composition.