Leak Repair

Call: 1-800-321-7212

Prime Flex 940 expansive polyurethane

Prime Flex 940 polyurethane resin is a very low viscosity, hydrophobic resin that reacts with water and expands to form a closed cell, watertight flexible foam. This grout requires Prime Kat or Kick Fast catalyst, but after mixing is pumped as a single component. The set time can be varied with the catalyst concentration. This resin is used for sealing actively leaking joints and cracks in concrete structures, particularly those subject to movement or vibration. 

Recommended Uses

Sealing active leaks in above- or below-grade concrete structures.
Filling voids where flexibility is required, including areas with vibration and minor movement


Typical Areas of Use

  • Pipe joints
  • Box culverts
  • Tunnels
  • Storm sewers
  • Retaining walls
  • Seawalls
  • Below-grade parking decks
  • Earthen dams



The foam’s flexibility allows it to expand and contract along with the structure it has sealed, so it remains watertight despite temperature fluctuations or minor movement. Its low viscosity makes it suitable for hairline cracks (though Prime Flex 900 XLV is a better choice for hairline cracks). As the foam reacts, it expands to fill the space, creating a closed-cell mass that does not allow water to pass through or around it.

  • Pumped as a single component
  • Controllable set time
  • Watertight
  • Very low viscosity for good penetration
  • MDI-based


Prime Flex 940:          
5 gallon pail

Prime Kat catalyst:
66 oz unit or 5 gallon pail

Kick Fast catalyst:             
66 oz unit or 5 gallon pail


Made in the U.S.A.