Why Bond Metal to Concrete?
Connecting metal elements to concrete is one of the most common structural operations in construction. Steel base plates, anchor plates, bearing plates, brackets, handrails, machinery frames, and strengthening plates all require reliable connections to concrete substrates.
Traditional methods use mechanical anchors (expansion bolts, cast-in anchors) to create point connections. Adhesive bonding creates a continuous connection across the entire contact surface, distributing load evenly and eliminating stress concentrations around bolt holes.
Two Bonding Approaches
Adhesive Bonding (Surface Bond)
The metal element is bonded directly to the concrete surface using a structural epoxy adhesive. The entire contact area transfers load through the adhesive layer. Our product: Steel Bonding Adhesive (XQ-JG) — thixotropic two-component epoxy with ≥ 14 MPa shear strength. Best for: Steel plate strengthening of beams and slabs, bracket connections, equipment base plates on smooth concrete, situations where drilling is not permitted (post-tensioned slabs, thin sections).Chemical Anchoring (Hole Bond)
Threaded rods or bolts are bonded into drilled holes using injectable adhesive. Load is transferred through bond stress along the embedded length. Our products: XQ-ZJ anchor adhesive range — epoxy, vinyl ester, and hybrid formulations in cartridge and bulk packaging. Best for: Base plate connections with high tensile loads, situations where the metal element cannot be removed for surface preparation, connections requiring mechanical fastener redundancy.Surface Preparation: The Key to Success
Both the metal and concrete surfaces must be properly prepared for a reliable bond.
Steel preparation: Remove all mill scale, rust, paint, oil, and contamination. Sandblasting to SA 2.5 standard (near-white metal) provides the best bond surface. The surface should be rough (Ra 50-75 μm) to provide mechanical interlock with the adhesive. Apply adhesive within 4 hours of blasting to prevent re-oxidation. Aluminum preparation: Degrease with solvent, then abrade with 80-grit sandpaper or scotch-brite pad. Aluminum oxide forms rapidly on freshly exposed surfaces, which actually improves bonding. Apply adhesive within 24 hours of preparation. Concrete preparation: Grind or sandblast to remove laitance, paint, and weak surface material. Expose aggregate to create a rough, open-pored surface. The concrete surface must be dry and structurally sound — pull-off strength of the prepared surface should exceed 1.5 MPa.Load Capacity Considerations
The shear capacity of a bonded metal-to-concrete connection depends on the adhesive shear strength, the bonded area, and the weakest link in the system (which is usually the concrete substrate, not the adhesive).
For our Steel Bonding Adhesive (XQ-JG) with ≥ 14 MPa shear strength, a 200mm × 300mm bonded steel plate can theoretically resist 840 kN in shear — far more than most practical applications require. The actual design capacity is typically limited by the concrete's surface tensile strength and appropriate safety factors.
Application Procedure for Steel Plate Bonding
For vertical or overhead bonding, our adhesive's thixotropic consistency prevents sagging or dripping. Temporary mechanical fixings (expansion bolts at corners) can hold the plate in position during cure without affecting the adhesive bond.
View our structural adhesives and anchor adhesives, or contact us for technical guidance.