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PU Injection Foam Resins

PU injection foam resins for fast stopping water

PU injection foam resins (PU foam) are designed for quickly and temporarily stopping water when repairing cracks. Injection foam resin is characterized especially by its strong increase in volume. It can also be used in case of highly pressing water often encountered in dam building, tunnel construction, bridge building and special civil engineering. 

WEBAC PU foam resin is compatible with concrete, steel, masonry mortar, foil and cable sheathing. WEBAC PU foam resins are also resistant to salts, lyes and acids detrimental to the building structure in concentrations usually found in building structures. A secondary injection with PU injection resins is carried out to obtain a permanent sealing effect.

Preparatory work

Structural analysis before the injection: 

  • Structural condition
  • Hydrodynamic and hydrostatic conditions
  • Water loads
  • Salt contamination

Please also note when repairing cracks: 

  • Crack characteristics (crack type, crack course, crack width, crack width modification, etc.)
  • Significance of cracks for the building structure

This provides information on: 

  • Cause of damage
  • Selection of suitable filling materials
  • Choice of drill-hole packers
  • Positioning of drill holes 

In the event of high flow rates, measures may be necessary to reduce the water flow and to prevent the filling material from being washed out. Possible measures are relief drillings and the installation of wooden wedges.


Application of injection foam resins

The injection pressure depends on the nature and condition of the building structure, the hydrodynamic and hydrostatic conditions and the desired filling level. Carry out the injection at intervals. Conclusions can thus be drawn from the reaction of the material, e. g. surface emergence, as to whether to continue or to stop the injection process. The reaction speed is influenced by the temperature of the material and the structural element: higher temperatures accelerate, lower temperatures slow down the reaction. Only inject pure WEBAC PU injection foam resins. They must be free of residues from cleaning agents or other foreign matter.

Application by 1C pump: 

  • Transfer the mixed material to the pump’s hopper
  • Stir briefly

Application by 2C pump: 

  • Provide for a sufficient volume flow to ensure that components A and B are mixed until homogenous in the mixing device (static mixer)

To ensure permanent limited-flexibility filling and sealing of cracks, a secondary injection with WEBAC PU injection resin is necessary when working with 2C PU injection resins. The product WEBAC® 155 does not require such a secondary injection.

Immediately after the injection of polyurethane foam resin, the secondary injection can usually be carried out via the same drill-hole packers. However, if the secondary injection is carried out several hours later it may be necessary to install new drill-hole packers.

Please also note when repairing cracks:

If water-bearing cracks under hydrostatic pressure require filling with PU foam according to  

  • ZTV-ING, part 3, section 4, no. 8.3/8.4, or 
  • Restoration Guideline, part 2,, prior to the injection, 

the filling process must be limited to the crack sections required to reduce water ingress.


PU injection foam resins: final work 

  • Upon conclusion of the injection and the curing process of WEBAC polyurethane injection foam resins or WEBAC PU injection resins used for the secondary injection, remove the packers
  • Close the drill holes with suitable mineral building materials