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Mountain Grout Flexible is a hydrophobic polyurethane injection grout for sealing active leaks through cracks and failed joints in concrete. When it reacts with water, it expands into a flexible, closed-cell foam that is suited to structures exposed to changing water levels and wet/dry cycles.
Where it works best
Use Flexible for leaking concrete joints and cracks in stormwater infrastructure, manholes, tunnels, underground vaults, lift pits and water-retaining structures. Unlike hydrophilic grouts that depend on retained moisture, the cured hydrophobic foam is selected for leak paths that may later dry out.
How it works
The system uses Mountain Grout Flexible base resin with MG Accelerator B. After the accelerator is mixed into the resin, the material is injected and reacts with water in the leak path. The accelerator dosage, temperature and amount of water encountered influence the reaction speed. The formulation can expand up to 30 times its initial liquid volume.
Choosing the right Mountain Grout
Choose Flexible when the seal needs to remain effective through wet/dry cycles. For persistently wet locations where a hydrophilic gel or foam is preferred, compare Gel Foam. For greater cured elongation in movement-prone cracks or joints, compare Mountain Grout Ultra.
Key considerations
- MG Accelerator B is part of the injection system and must be used in the appropriate proportion for site conditions.
- Reaction speed is affected by temperature and available water, so published times are not universal site guarantees.
- Use a specialist injection method appropriate to the crack, joint and water conditions.
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 % |