Polyurethane Grouting - Foundation Professionals of Florida

Slab lifting with polyurethane foam

A very popular application for polyurethane foam is to lift and re-level sunken concrete slabs (slab jacking). By drilling holes through the slab and injecting the expanding foam, slabs are accurately lifted back to their original grade. If deep, loose soils are to blame for the slab settlement, the compaction grouting should be performed prior to completing the slab lift. After the slab is lifted, the holes are cleaned and patched with a cementitious or high strength epoxy grout. After polyurethane foam injection, sunken driveways are ready for vehicular traffic immediately due to the fast reaction and curing time of the structural foam.

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Polyurethane grout for void filling

Polyurethane grouts are a lightweight, high capacity, and environmentally safe option for filling underground voids. As compared with cement grout for void filling, the lightweight nature of polyurethane foam minimizes the potential for additional sinking/settling (heavy cement may sink/settle further into the soil with time).

Soil stabilization with polyurethane grouts

Injecting polyurethane resins and gels into loose soils, voids, pores, and fissures increases strength, stiffness, solidifies and provides watertight encapsulation. There are a variety of polyurethane grouts ranging in viscosity, reaction time, reaction with water, expansion characteristics, and flexibility of cured grout to match the soil conditions as well as project objectives.

Reduce I&I into manholes and sewer lines with polyurethane grouting

Polyurethane curtain grouting has proven to be a highly effective means to control inflow and infiltration into manholes and sanitary sewer systems. Polyurethane grouts can be injected directly through the walls of manholes and sewer structures forming a watertight barrier between the soil and structure. This minimizes/reduces the potential for groundwater to make contact with the sewer pipes or structures.

Waterproofing basements, tunnels and other underground structures

Using the curtain grouting or probe grouting method, polyurethane grouts can be used to create a watertight barrier between groundwater and underground structures. By drilling holes through the walls and/or floors and injecting a polyurethane gel or foam, a watertight barrier is created, minimizing groundwater from making contact with the structure.

Stop gushing leaks (up to 15,000 GPM) with polyurethane grouts

Polyurethane grouts have been used to stop active, gushing leaks in tunnels up to 15,000 gallons per minute. High-pressure pumps and highly expansive two-part expanding polyurethane foam can be used to quickly inject and seal off high volume leaks. Once the stream is reduced significantly, hydrophilic polyurethane gels can be used to seal the remaining leaks and complement the existing foam.

Advantages of polyurethane grouts:

• Lightweight
• High-Capacity
• Non-Invasive
• Accurate Lift
• Waterproof
• Fast Cure Time
• Environmentally Safe
• Target Grout Injection (TGI)

Hydrophilic vs Hydrophobic

Hydrophilic is derived from the Latin, with “hydro” meaning “water” and “philic” meaning loving. So hydrophilic grouts “love” and actively seek out and react with water creating a tight bond with wet concrete. Hydrophilic chemical grouts can produce either closed-cell foam or non-cellular gel when mixed with water. When activated, foams can expand to 5-8 times their volume.

Hydrophobic is just the opposite of hydrophilic. Hydrophobic means “water-fearing”. A hydrophobic polyurethane grout pushes water away further into the substrate as it makes contact – creating an impermeable mass of soil-grout. Hydrophobic polyurethane grouts require a catalyst to be mixed into the resin prior to injection. The measure of catalyst mixed in controls the expansion speed and volume – using the maximum ratio of catalyst (10% by volume) the foam can expand to 29 times in volume in just 10-12 seconds.

Foundation Professionals of Florida has used polyurethane grouts on small residential slab lifting and basement waterproofing projects to large sewer structure grouting and soil stabilization projects. We service 9 states including Florida, Georgia, Alabama, Mississippi, South Carolina, North Carolina, Tennessee, Kentucky, Virginia as well as the Virgin Islands and the Florida Keys.

With over 40 years of experience and multiple awards as a geotechnical contractor – we welcome the opportunity to bid on your next project requiring polyurethane grouting. Contact us today for a free estimate.

There are many options for repairing leaks in concrete structures. One of the oldest, yet least understood repair methods utilizes polyurethane chemical grouts that react with water.  They either bond with the concrete to form watertight, permanent seals or become rigid to fill voids and stabilize the soil. 

According to the National Association of Sewer Service Companies (NASSCO), chemical grouting was first developed in . Since that time, it has been used in sewers, manholes, tanks, tunnels, and many other applications all over the world. More than 40 years later, it’s still a cost-effective, long-term defense against infiltration of groundwater into structurally sound sewer systems.

Reducing Infiltration

Municipalities are frequently seeking effective repair options to ease the load on their water treatment plants by reduce groundwater infiltration. 

Infiltration occurs when leaks in sewer lines, manholes, pump stations, and storm drains allow groundwater to enter the system. This infiltration adds to treatment costs and increases the risk of sanitary sewer overflows (SSOs). Groundwater leaks also carry sand, silt, and other debris into the system, increasing wear and tear on equipment. 

Leaks can also create voids and in extreme cases, undermine structures, leading to unstable foundations and settlement. 

Studies show that 40% of groundwater infiltration in sewer systems enters through manholes. Repair usually involves a waterproof liner, but groundwater infiltration must be eliminated prior to installing the lining. 

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Many contractors use a quick-set hydraulic cement, which stops the leak temporarily, and provides enough time for the lining to be installed. But this type of patch is actually quite temporary, and can lead to a weak bond and failure of the lining system.

With polyurethane grout, leaks can be stopped in a matter of seconds, permanently and with immediate cost-savings.

Installation

Polyurethane chemical grouts are usually sold as liquid resins injected into or around the leak. Once the resin contacts water, a chemical reaction occurs and it expands into a closed cell foam. The foam created can be flexible and resilient (hydrophilic) or rigid (hydrophobic). 

To inject the resin, a hole is drilled in the vicinity of the leak and the chemical grout is injected through the wall into the water source. The force of the water pushes the material back into the structure and seals the leak from the outside, so the seal penetrates the entire wall.  

Choosing the Product

Choosing the right material has a great impact on the longevity of the repair, and there is not a single product on the market today that is a “fix-all, do-all” for repairing  leaks in concrete.  While many products will temporarily fix a leak, only a few will be permanent, and those must be applied correctly by trained applicators.  

Knowing the differences in hydrophobic and hydrophilic chemical grouts is a crucial.

Hydrophilic Grouts: These products produce a closed cell foam when mixed with water. The reaction time is typically 30 to 45 seconds, and they expand five to eight times the initial volume. “Hydrophilic” means “water-loving” in Greek, and is able to bond exceptionally well to wet surfaces. The resin can even work its way into water-filled pores in the concrete. Hydrophilic chemical grouts are flexible and resilient after full cure and will allow movement to occur in the structure without damaging the seal or bond. 

Hydrophobic Grouts: These are two-part grouts.  They require a catalyst, blended into the resin prior to installation, in order to expand. The amount of catalyst controls the reaction time and the volume of foam. Using the maximum dosage of catalyst, (10% by volume), hydrophobic resins have an aggressive expansion—as much as 29 times in volume—and the reaction time is 10-12 seconds.

Hydrophobic chemical grouts repel water after activation, but when injected into a wet crack, hydrophobic resins can trap water in the pores of the wet concrete. This trapped water becomes a bond inhibitor. Hydrophobic resins cure to a rigid, hard foam, and do not recover if compressed, so if the structure moves there is good chance the cell structure will be damaged and leaks will reappear. 

Hydrophobic chemical grout is used for foundation stabilization and soil consolidation. It’s low viscosity (fairly runny) so it permeates loose and non-consolidated soils easily. 

If the repair project involves a non-structural defect in concrete or masonry, a hydrophilic chemical grout should probably be used to seal the leak.

Hydrophilic foams are appropriate sealing water leaks above-grade and below. They are typically 85% air after expansion, and have excellent elongation, compression and rebound for use in expansion joints, cracks, or any other non-structural defect in concrete structures.

Hydrophobic grouts are best for filling voids that may be present outside the structure. If the job is below-grade and involves a gushing leak that is impractical to repair with hydrophilic resins. Hydrophobic resins can be used to fill the void.  Then, once the leak is reduced to a manageable level, hydrophilic resin should be injected into the defect to back up the hydrophobic material.

Conclusion

As America’s infrastructure ages, grouting will continue to maintain its value as one of the easiest, most cost-effective and longest-lasting repair solutions available. 

If the right polyurethane grout is chosen, and the correct installation techniques are used, the repair will actually outlast the structure.

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