Repair Systems — Concrete & Structural Defects
PU joint sealants
Technical product reference for polyurethane, MS-polymer, and silicone sealants for surface sealing of movement cracks, control joints, and construction joints in concrete — covers chemistry selection, movement capability, paintability, and joint geometry requirements for Australian structures.
Sealant joint geometry — why backer rod depth matters
The single most common sealant failure in concrete crack and joint sealing is incorrect joint geometry — too deep a sealant fill without a backer rod. The sealant depth should be half the joint width (depth:width 1:2). Without a backer rod, sealant fills the full depth of the joint, creating a thick, rigid plug that tears when the joint moves rather than stretching.
Product Reference
Individual products — one card each — scroll to view all
Sika Australia
Sika Sikaflex-11FC
1-component PU gun-grade sealant & adhesive for joints and cracks
Sika Sikaflex-11FC is a one-component, moisture-curing, gun-grade polyurethane sealant and adhesive for sealing and bonding movement cracks and joints in concrete. Elastic and overpaintable. CONFIRM the movement capacity, primer requirement and joint design against the current Sika Australia TDS.
Ardex Australia
Ardex RA 040
1-component polyurethane joint sealant
Ardex RA 040 is a one-component, moisture-curing polyurethane joint sealant for movement joints and cracks in concrete. CONFIRM the movement capacity, trafficability, primer requirement and pack size against the current Ardex Australia TDS.
Fosroc / Parchem
Fosroc Nitoseal PU400
1-component trafficable PU expansion-joint sealant (AS 4020)
Fosroc Nitoseal PU400 is a one-component, trafficable polyurethane expansion-joint sealant suited to movement and expansion joints in trafficked decks and water-retaining structures, with AS 4020 potable-water contact (confirm). CONFIRM the movement capacity, potable-water scope and joint design against the current Fosroc / Parchem TDS.
System Comparison
Polyurethane sealants — confirm all selections against the current manufacturer TDS before specifying.
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Do not confuse PU joint sealants with:
- PU flexible injection resins — polyurethane injection resins (Sika Injection-107, Mapei Mapeject PU) are pumped under pressure through surface ports deep into crack traces; PU sealants are applied as a gun-applied surface bead over a backer rod in routed joints — surface treatment only, no penetration into the crack depth
- Epoxy rigid crack injection resins — epoxy injection resins structurally re-join dormant crack faces at 15–20 MPa tensile bond; PU sealants accommodate surface movement and seal against water ingress but do not restore structural tensile capacity — wrong product for structural crack repair
- Backer rods — closed-cell PE foam backer rods and bond-breaker tape are accessories installed before sealant application to control sealant depth and prevent three-sided adhesion; they are not sealants and must be specified alongside, not instead of, the sealant
- General gap fillers and caulking compounds — retail acrylic or silicone gap fillers (no movement rating, no MS or ISO 11600 classification) are not appropriate for concrete joint sealing where ±25% movement is required — never substitute unrated gap filler in expansion or control joint applications
- Cementitious repair mortars — flexible render and mortar patching compounds are not sealants; they cannot tolerate cyclic joint movement and will crack if applied over an active concrete movement joint
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.