Preparing concrete for a resin floor

The short answerConcrete for a resin floor must be sound, with a minimum compressive strength of 25 N/mm² and tensile strength of 1.5 N/mm², free of cracks, voids, laitance, dust, oil and contamination, and dry to 75% relative humidity with no rising damp. Remove laitance by blasting, scarifying or diamond grinding, and repair cracks and damage with an epoxy filler.

Most resin floor failures start below the surface. The best product in the world will not stay bonded to weak, damp or dirty concrete. ASP's technical data sheets set out the same requirements for every system.

What the substrate needs

• Strength: a minimum compressive strength of 25 N/mm² and a minimum tensile strength of 1.5 N/mm².
• Soundness: able to bear loads, free of cracks and voids.
• Cleanliness: free from laitance, dust, oil and other contamination.
• Moisture: dry to 75% relative humidity, with no rising damp or ground water.
• Profile and levels: appropriate for the system being applied.

Preparation methods

Laitance, the weak surface layer on new concrete, has to come off. ASP's sheets allow blasting, scarifying or diamond grinding, depending on the system. Irregularities, small damage and cracks are then repaired with an epoxy filler.

Anchor grooves for polyurethane and vinyl ester screeds

Heavy polyurethane and vinyl ester screeds need anchor grooves cut before application: about 6 mm deep by 6 mm wide for a 6 mm system and 9 mm by 9 mm for a 9 mm system, 25 mm either side of expansion joints, saw cuts and floor edges.

Priming

A primer seals the concrete and promotes adhesion. ASP-primeStd is a low viscosity, solvent-free epoxy primer applied at 4 m²/litre. Work it well into the surface; on porous concrete apply more until the surface is completely wetted out, and avoid ponding. Many systems call for scatter sand broadcast into the wet primer at 1 kg/m².

Damp or oily concrete

If there is rising damp, a ground water problem or oil that has soaked into the concrete, stop and talk to ASP's technical team. They will recommend a preparation method or a moisture tolerant system such as ASP-primeDamp. The water-based ASP-coatWBE can be applied to damp or green concrete for light duty areas.