Inadequate surface preparation can lead to loss of adhesion and failure of resin coatings. Grinding, shot-blasting or planing is recommended. Scabbling or acid etching are not recommended. Substrates must be sound, clean and free from contaminants.
New concrete bases should be a minimum of Grade RC30 of BS 8500-2: 2002 and not contain a water repellent ad-mixture. The surface strength of concrete bases should exceed 1.5 MPa. The laitance and any surface sealer or curing membrane should be removed by mechanical grinding to expose the coarse aggregate. After surface preparation, the loose debris and dirt should be removed by vacuum. For concrete bases in contact with the ground, a damp-proof membrane should have been incorporated into the slab design, in accordance with the requirements of CP102 (Code of Practice for Protection of Buildings Against Water from the Ground).
All laitance and surface contamination- oil, paint and rubber should be removed by mechanical means to expose the coarse aggregate. After surface preparation, all loose debris and dirt should be removed by vacuum equipment. Any weak or suspect concrete must be removed and repaired using suitable materials. Heavy oil / grease should be removed either mechanically, by steam cleaning or by chemical treatment then by high pressure water blasting followed by the application of an epoxy primer. The surface should be visibly dry before application. If oil or grease contamination has been severe or long lasting, none of these methods may prove satisfactory and in the concrete base would need removing. In existing buildings without a damp-proof membrane, the application of an epoxy DPM should be considered.
Concrete Moisture Content
The base should have a relative humidity at the surface of not more than 75% when measured by the test method described in BS 8203. However, certain resin flooring systems are tolerant of higher moisture levels in the concrete base. Refer to product TDS for specific information.
Badly Pitted Concrete
If, after surface preparation, the concrete surface is badly pitted it is recommended that, after priming, a scratch coat of flow applied flooring is applied to fill in the voids prior to the application of the final finish. Failure to do so could result in a poor finish.
Timber floors should be minimum 25 mm thick tongue and grooved marine plywood fixed with counter sunk screws at minimum 30 cm centres. All joints should be staggered, glued using PVA based adhesive and reinforced with glass fibre scrim approx 100 mm wide. They must be protected from rising moisture by a damp proof membrane.
Mild steel must be free from oil and grease and rust or mill scale must be removed. The preferred method of preparation is by shot blasting. Metal edging strips should be fixed to protect the edges of the resin flooring.
Asphalt surfaces should be degreased and abraded. Resin coatings will follow the surface profile of the substrate. The required standards for flatness and regularity should therefore be provided by the prepared substrate. This is especially important where flow applied resin finishes are specified. A minimum slope of 1 in 80 should be specified to provide a free draining floor and textured surfaces may require a higher slope.
Movement joints in the substrate must be carried through the resin floor finish. When forming expansion joints around columns and machine beds, the corners should have a minimum radius of 5 cm to avoid stress cracking. Expansion joints should also be formed around areas subject to vibration or differential thermal movement (ovens, cold stores and vibrating process equipment). It is good practice to install clay tiles and a heat shield in oven areas. Grids should be installed where hot wheeled trolleys are moved from ovens onto resin flooring.
Surface Preparation Techniques-
- Shot Blasting
Shot blasting involves a steel abrasive being propelled at high velocity onto a surface. The debris and dust is collected by a vacuum unit and the shot is recycled for re-use. Shot blasting will produce an effect known as tram-lining which can still be visible following application of epoxy coatings and can highlight defects in the surface. Shot blasting works well on concrete, steel and some asphalt surfaces. It is not suitable to prepare soft screeds, soft bitumous materials and will not remove materials over 500 microns or elastomeric materials.
Planing/Scabbling is based on a rotating drum fitted with hard metal teeth. This technique is useful for removing materials in excess of 1 mm and softer products. However planing produces a more profiled floor than other techniques and it may therefore be necessary to employ further preparation to reduce the surface imperfections.
Grinding is carried out with diamond, tungsten or resin bonded discs attached to single or multiple rotating heads. Choosing of the correct discs is essential to achieve the desired result. Grinding can be successfully applied to concrete and some asphalt surfaces. Grinding may produce a swirling pattern on the surface which may still be visible following application of epoxy coatings and can leave troughs unless sufficient material is removed to reach the lowest level of the floor surface. It is important that an effective mechanical key is obtained as grinding can polish the surface and reduce the ability of the primer to penetrate sufficiently.
- Multi Stripping
Multi-stripping involves a blade fitted to the front of a machine used to remove existing floor coverings such as vinyl & carpet tiles.
Holes, cracks and other damage should be repaired using suitable materials prior to applying the epoxy resin coating
Difficult / unsuitable substrates for resin flooring include galvanised steel, stainless steel, copper, aluminium & wood (except exterior grade plywood), asphalt/bitumen, non-porous tiles and magnesite.
Be sure to check references of painting contractors before choosing one as it pays to get the job don properly the first time.