Ardex RA 88 Plus Multi-Purpose Epoxy Repair Adhesive

For horizontal, vertical, and overhead concrete repairs, ARDEX RA 88 Plus is a non-drip, non-sag epoxy adhesive that fills holes, seals cracks, and sets anchor bolts. It is formulated to bond structurally to major construction substrates—including metal, concrete, brick, wood, stone, and block—and meets AS/NZS 4020 for contact with potable drinking water.

What it does

ARDEX RA 88 Plus is a two-component epoxy that cures to a high compressive strength of 87 MPa, making it suitable for structural repairs and spall patching. Its paste consistency allows it to be trowelled flush into overhead or vertical gaps without running or sagging. The adhesive serves as a chemical anchor for bolts, a rigid seal for crack injection ports, and a high-strength termination sealant for selected ARDEX Sheet Applied Waterproofing Membranes inside prepared reglets. In swimming pools, its density allows underwater installation of tiles on side walls or bottom surfaces when applied to a dry tile.

Numbers that matter

• 87 MPa compressive strength (ASTM D695): High-load resistance for structural concrete patching and anchor bolt installations after a 7-day cure.
• 20.1 MPa bond strength (ASTM C882): High-strength adhesion when bonding hardened concrete to hardened concrete after 14 days.
• 3-hour tack-free cure (at 24°C): Rapid curing window that allows the epoxy to be ground mechanically, painted, or opened to full traffic after 3 hours.
• 45-minute working time (at 24°C): Practical wet-edge window to align tiles, secure injection ports, or trowel spalls flush before curing begins. Working time drops to 20 minutes at 40°C and extends to 90 minutes at 4°C.
• 0.00015% shrinkage (ASTM D2566): Negligible shrinkage at 48 hours, preventing tension cracks or bond-line failures along concrete joints.

Where to use it

• Waterproofing terminations: Sealing reglets and fixing Over-Flashing details for selected ARDEX Sheet Applied Waterproofing Membranes.
• Concrete spall repairs: Patching ground-down spalls between 13mm and 16mm deep, and up to 76mm wide.
• Crack injection: Adhering injection ports and sealing the face of cracks prior to injecting epoxy repair resins.
• Rigid bonding: Structural bonding of metal, brick, stone, block, wood, and concrete.
• Pool maintenance: Replacing dislodged tiles underwater along pool walls and floors.

Limitations

• Do not use ARDEX RA 88 Plus to repair cracks subject to movement.
• Designed for small patch repairs only. Deep or large-mass repairs will generate excessive chemical reaction heat, which can cause swelling, smoking, and cracking.
• Do not thin the product with solvents, as this will prevent curing.
• Not recommended for vertical crack or spall repairs underwater; underwater use is restricted to replacing tiles.
• The cured epoxy may discolour under UV exposure.
• If overcoating with paints or architectural coatings, avoid solvent-based coatings. Sanding the cured surface first is required to aid coating adhesion.

How to apply

Ensure concrete substrates are a minimum of 28 days old. All concrete surfaces must be clean and mechanically prepared by rough-grinding, scarifying, or bush hammering to achieve a roughened profile. Smooth surfaces like wood or metal must be mechanically roughened with a wire brush or sandpaper. All dust, dirt, oil, and contaminants must be removed by vacuuming prior to application.

To prepare the cartridge, unscrew the plastic cap, remove the plug, and load the cartridge into an ARDEX Heavy Duty Caulking Gun (use the 254ml gun for the 254ml size, or the dual-cartridge gun for the 627ml size). Dispense a small amount of material until both parts flow evenly. Attach the mixing nozzle and purge a small amount of product until the paste has a consistent grey colour with no streaks.

Substrate and ambient air temperatures must be between 5°C and 35°C. If the work site or substrate is below 21°C, condition the cartridges to 21°C–24°C before use to prevent the product from thickening. Clean tools immediately with a mild solvent; cured epoxy can only be removed mechanically. The adhesive must be fully cured before conducting any water flood testing on waterproofing membranes.