Before the advent of carbon composites, bonding steel plates was a go-to technique for strengthening concrete members. It remains a valuable solution, particularly for very high-strength requirements or where steel sections are being added. Key aspects of steel bonding and anchoring include:

• Steel Plate Bonding (Epoxy Jacketing): In this method, steel plates (often 4–6 mm thick) are attached to concrete elements (such as the underside of beams or the sides of columns) using a structural epoxy adhesive. ZRETE’s JGN801 Steel Structure Adhesive and JGN803 Steel Jacketing Adhesive are examples of two-component modified epoxy resins formulated for this purpose. They offer:

• High Bond Strength: Achieving a strong chemical and mechanical bond between steel and concrete, with adhesion often exceeding the tensile strength of concrete (i.e., failure occurs in concrete before the glue line gives way).

• Thixotropic, Gap-Filling Properties: The adhesives are paste-like, so they don’t run on vertical or overhead surfaces, and they can fill small gaps or unevenness between plate and substrate. This is crucial for full surface contact.

• Durability: Once cured, these epoxies are extremely durable – resistant to vibrations, impacts, and environmental attacks (water, acids, alkalis) They are also available in formulations for low temperature or damp conditions (e.g., JGN801 comes in normal and low-temp versions).

• Application: The process involves surface preparation (concrete is roughened and cleaned; steel plate is sand-blasted and cleaned), then mixing the epoxy (usually a 3:1 or 2:1 ratio resin to hardener) and applying it evenly. The plate is pressed onto the concrete (often temporary props or bolts hold it until cured). No welding is needed, and curing occurs at ambient temperature over 24–48 hours to achieve high strength. The result is an effectively monolithic bond.

• Steel Anchoring (Chemical Anchors): Often in structural upgrades, you need to add new reinforcement bars or anchor bolts – for example, to anchor a new steel beam to an existing column, or to post-install rebar for a concrete extension. Epoxy anchoring adhesives like JGN805 Modified Epoxy Resin Anchor Adhesive make this possible. Key points:

• High Load Capacity: A properly installed adhesive anchor can achieve pull-out strength comparable to or exceeding cast-in-place bars. JGN805, for instance, develops extremely high bond strength to concrete and steel, ensuring the embedded bar can carry heavy loads (tensile, shear) without slipping.

• Versatility: It can anchor various elements – reinforcing rebars for new concrete sections, threaded rods for connecting structural steel, bolts for machinery bases, etc. The same material can be used in infrastructure retrofit (bridges, buildings) and even in marine or high-humidity conditions if specified.

• Installation: Typically a hole is drilled into the concrete, cleaned thoroughly, then the epoxy is injected and the bar inserted. JGN805 is a two-part system that can be dispensed through a cartridge or mixed and poured, depending on packaging. It’s solvent-free and cures without significant shrinkage. After curing, the anchored element is permanently fixed.

• Durability & Toughness: JGN805 is formulated for toughness and longevity – it resists impact, vibrations, chemicals, and water ingress. That is critical as anchor bars often carry dynamic loads or are in outdoor conditions.

Historically, steel plate bonding was one of the earliest strengthening techniques, and while composite materials have gained popularity, steel bonding remains relevant. For example, in situations requiring very high stiffness addition, a steel plate’s Young’s modulus (≈200 GPa) can be advantageous. ZRETE’s adhesives allow engineers to implement this method reliably. It’s also common to use bolts in conjunction with epoxy for very large plates as a safety measure (bolts at the plate ends prevent peeling). But for many applications, the epoxy alone is sufficient and preserves the member’s appearance (no through-bolts needed on the face).

Products (Steel Bonding & Anchoring):

• Steel Bonding & Jacketing Adhesive – (JGN801/JGN803) Two-component modified epoxy adhesives for bonding steel plates to concrete. Provides high-strength, durable bonding for external steel reinforcement on beams, columns, slabs, and for steel jacketing of concrete elements.

• JGN805 Modified Epoxy Resin Anchor Adhesive – High-performance chemical anchoring epoxy for fixing rebar dowels, anchor bolts, threaded rods into concrete. Ensures secure anchorage for structural connections and retrofits.

(Steel bonding is frequently used in bridge upgrades (e.g., bonding steel plates under bridge girders), and building retrofits where headroom constraints prevent thickening the member. Anchor adhesives are widely used from seismic retrofit projects (adding new hold-downs, shear wall ties) to industrial installations (anchoring heavy equipment). These epoxy systems have decades of proven use, with the steel plate bonding technique having been pioneered over 50 years ago– modern formulations like ZRETE’s make it even more reliable and user-friendly.)