Hydrophilic Grout Systems


Hydrophilic expansive grouts react upon contact with water, absorb water while curing,and cure to a flexible foam or gel. They are generally used to seal leaks in joints or cracks and to repair leaking water-stops. Hydrophilic expansive foam grouts chase and absorb the water in the crack and in all of the fractures that branch off from the main crack. A key characteristic of any liquid is its viscosity (cps) compared to water. Water has a cps of 1, where hydrophilic expansive grouts could range from 300-2500 cps. The lower the cps (the lower the viscosity) of any hydrophilic expansive grout the better suited for tighter cracks (for better penetration) and for applications that might require greater travel. The higher the cps (the higher the viscosity) of any hydrophilic expansive grout the better suited for high flow/high volume applications so as not to become diluted. Hydrophilic gel grouts work by stabilizing the soil outside the structure, like acrylamide.The grout prepolymer is usually mixed with water at ratios of 6:1, 8:1, and up to 12:1 (water to polymer ratio) to obtain a gel ranging from firm to weak.


Hydrophilic expansive foam grouts have an initial cure and final cure. The initial cure is the time it takes for the polyurethane grout to foam up, and the final cure is the time it takes for the grout to fully expand. This final cure time, which may take up to 12 hours,is critical to the success of the grouting process. Hydrophilic foams have been successfully used in above- as well as below-grade applications, but hydrophilic gels should be used below grade as they will shrink in a dry environment. Hydrophilic expansive gel grouts can be mixed with large amounts of water to offer an alternative grouting material in areas such as curtain grouting, manhole grouting, and soil stabilization. Most polyurethane grouts are considered to be “non toxic” although safe handling procedures should be closely followed with these and all other chemicals.Hydrophilic expansive foam grouts are typically single component products requiring small delivery systems for the injection process. These types of grouts are used in below grade structures, basements, and other areas that are often wet, such as subways and interior portions of a concrete dam. If injecting a hydrophilic gel grout for soil stabilization, manhole grouting, or curtain grouting a multi-ratio delivery system would be needed. Pumping systems for hydrophilic foam grouts tend to be high pressure and low volume, while the gels utilize high volume and lower pressure systems.Some hydrophilic foam grouts are certified to be used with potable drinking water systems. These hydrophilic grouts have been certified by UL or by NSF if used in accord with the American National Standards Institute (ANSI) 61 testing standards.Typical costs for a hydrophilic grout range from $45 to $65 per gallon. The expansion rate of hydrophilic foam grouts can be up to 5 to 7 times its original volume, and hydrophilic gels typically do not gain volume upon curing.