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For sealing leaking cracks and failed joints in concrete structures under wet/dry cycles, Mountain Grout Flexible provides a hydrophobic barrier that resists shrinkage. When injected into storm water systems, tunnels, manholes, or concrete dams, this closed-cell polyurethane foam reacts with moisture to form an inert, permanent seal that accommodates structural movement without losing adhesion.
How it works
Mountain Grout Flexible is a low-viscosity, hydrophobic polyurethane system consisting of an amber base resin and Accelerator B. Unlike hydrophilic grouts that require constant moisture to maintain their volume, this hydrophobic formulation reacts with minimal water to form a stable closed-cell foam. Because the cured grout does not rely on retained water, it will not shrink or lose its seal when water tables drop or joints dry out. The system pumps as a single component after mixing the base resin and accelerator, allowing the installer to adjust the reaction profile on-site to match the water flow and temperature of the concrete substrate.
Where to use it
- Concrete dams and earthen dams
- Waste treatment plants and water-related facilities
- Storm water systems and manhole facilities
- Tunnels and underground vaults
- Elevator pits and parking garages
Numbers that matter
- 44% elongation (ASTM D-638): High flexibility to absorb joint expansion and contraction in concrete structures without tearing or delaminating.
- Up to 30x expansion: Expands up to 30 times its initial liquid volume to fill deep voids and wide cracks behind leaking concrete walls.
- <1% water absorption (ASTM D-2842): Highly impermeable closed-cell structure prevents water migration through the cured seal.
- 500 cps base viscosity (ASTM D-1638): Low viscosity allows deep penetration into fine fractures and tight concrete joints before reaction begins.
- 15-second to 50-second initiation windows: Reaction speeds are controlled by the dosage of Accelerator B at 25ºC, letting installers match the foam rise to the water pressure.
Controlling reaction times
The reaction profile must be adjusted prior to pumping by mixing Accelerator B into the base resin. The speed of the expansion is determined by the accelerator dosage, substrate temperature, and the amount of moisture encountered. At 25ºC, the reaction times are:
- At 1.25% dosage (1/2 pint per 5 gallons): Expansion starts in approximately 50 seconds and completes in approximately 4 minutes after encountering water.
- At 2.5% dosage (1 pint per 5 gallons): Expansion starts in approximately 15 seconds and completes in approximately 65 seconds after encountering water.
How is the reaction time adjusted?
Add Mountain Grout Accelerator to the base resin before pumping. At 77°F with 2.5% added water, 1.25% Accelerator gives about 50 seconds to expansion start and 4 minutes to completion, while 2.5% gives about 15 seconds to start and 65 seconds to completion.
- Concrete cracks and failed joints
- Rock fractures in tunnelling and mining applications
Mountain Grout Flexible Physical Properties
| Property | Value |
|---|---|
| Base Chemistry | Hydrophobic polyurethane |
| Curing System | Single-component |
| Density | 64 kg/m³ |
| Viscosity Base Resin | 500 mPa·s |
| Viscosity Accelerator B | 25 mPa·s |
| Flash Point Base Resin | >121°C |
| Flash Point Accelerator B | 107°C |
| Tensile Strength | 0.20 MPa |
| Bond Strength | 0.12 MPa |
| Elongation | 44% |
| Expansion Ratio | Up to 30x |
| Cure Rate | Start ~15 s, complete ~65 s (with 2.5% Accelerator B at 25°C) |
| Water Resistance | <1% |
| Substrate Compatibility | Cracked/damp concrete, construction joints, manholes, tunnels, dams, vaults, elevator pits, parking structures |
| VOC Content | No VOCs (100% solids) |
| Viscosity | 500 cps |
| Specific Gravity | 1.15 |
| Flash Point | >121ºC |
| Water Absorption | <1 % |