Repair Systems — Concrete & Structural Defects
PU flexible injection resins
Technical product reference for polyurethane flexible injection resins used to seal wet and live cracks in concrete — covers hydrophilic and hydrophobic PU resins, foaming vs non-foaming types, and system selection criteria for Australian structural repair.
PU flexible injection vs epoxy rigid — choosing the right resin
Polyurethane flexible injection resins are used to seal water-active (wet, leaking) cracks and to provide a flexible seal in cracks that are moving. PU resins react with moisture to foam and expand, filling the crack void and blocking water passage. Unlike epoxy rigid injection, PU resins do not reinstate tensile capacity across the crack — they seal without bonding.
Product Reference
Individual products — one card each — scroll to view all
Sika Australia
Sika Injection-111 (+ Injection-111C)
1-component hydrophobic water-reactive PU foam injection resin
Sika Injection-111 is a one-component, hydrophobic, MDI-based water-reactive polyurethane that foams on contact with water to a durable closed-cell foam, sealing actively leaking cracks. Reaction speed is adjusted with the Injection-111C accelerator. It seals water — it does not restore structural load transfer (use a rigid epoxy for that). CONFIRM accelerator dose and pack sizes against the current Sika Australia TDS.
Fosroc / Parchem
Fosroc Nitofill PU130
Hydrophobic semi-flexible PU injection resin
Fosroc Nitofill PU130 is a hydrophobic, semi-flexible water-reactive polyurethane injection resin for sealing actively leaking cracks in concrete and masonry, tolerating minor movement. It seals water rather than restoring structural load transfer. CONFIRM components, mix ratio and pack sizes against the current Fosroc / Parchem TDS.
Mapei Australia
Mapei Resfoam 1KM
1-component water-reactive foaming PU injection resin
Mapei Resfoam 1KM is a one-component, water-reactive foaming polyurethane injection resin that expands rapidly on contact with water to cut off flow in wet, actively-leaking cracks and voids. It seals water rather than restoring structural load transfer. CONFIRM accelerator use and pack sizes against the current Mapei Australia TDS.
Other / Generic
Hydrophilic PU water-stop resin (generic)
Single-component hydrophilic PU — water-swelling gel seal
A hydrophilic polyurethane water-stop resin is a single-component, water-reactive resin that swells/gels on contact with water to seal moving or intermittently-wet cracks and construction joints, accommodating more movement than a rigid foam. Hydrophilic gels can shrink if the crack dries fully — confirm suitability for the wet/dry cycle. This is a generic type; confirm the specific proprietary product and its TDS.
System Comparison
Flexible PU injection resins — confirm all selections against the current manufacturer TDS before specifying.
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Do not confuse PU flexible injection resins with:
- Epoxy rigid injection resins — epoxy resins (Sika Injection-451, Fosroc Concresive 1414) restore structural capacity by fusing crack faces into a bond stronger than the concrete; PU flexible resins seal cracks against water ingress only and have no structural function
- PU joint sealants — surface-applied PU sealants (Sikaflex-11FC, Fosroc Nitoseal MS300) are applied as a bead over a backer rod in routed joints at the concrete surface; PU injection resins are pumped under pressure through ports deep into the crack trace
- Cementitious crystalline waterproofing — products such as Xypex and Vandex penetrate the concrete matrix and block capillary pores; PU injection resins seal crack voids by physical filling and flexible bonding — different mechanism and application method
- Cementitious grout injection — Portland cement or neat cement grout injection is used for ground anchors and rock mass stabilisation; PU injection resins are specified for tight cracks in concrete elements, not void grouting
- PU injection pump equipment — pressure injection equipment (packers, pumps, hoses) is the delivery hardware; the injection resin is the reactive chemical product — equipment and resin are specified separately
Disclaimer
This page provides general technical information only. Final product selection must be confirmed against the current manufacturer TDS, project specification, substrate condition, and applicable standards. Do not rely on this reference as a substitute for professional engineering advice.