Preparation is the key.............
A D.I.Y. job doesn't have to be a poor relation to a professional project, usually the part that the pro's concentrate on is skimped on by the layman, the main reason for this is not being aware of what tools are out there that can help with this task. The main emphasis should be on achieving a clean, dry floor (although we have some damp tolerant products), that is free from grease, oil and loose impediments. The best way to achieve that is by mechanical means, if you are over coating existing painted floors, then the main emphasis is removing grease and oil etc, this is best achieved by using a floor scrubber drier with the correct detergent/degreaser, followed by mechanical abrasion to give a key for the new coating, this is best achieved with an STR type grinder with the appropriate pads.
Old uncoated concrete is relatively easy to prepare with a variety of grinding and planing machines on the market, diamond grinding usually being the best and quickest option.
New concrete can provide a few challenges, first of all how long has it been down? Concrete takes a while to release the moisture from the slab and a number of factors, not least the water/cement ratio, affect this, however, without wishing to get too technical an accepted "rule of thumb" time for a slab to dry out would be in the region of 4 weeks for every 25mm thickness, i.e. A 100mm thick ground floor slab drying from one side would take 4 months to dry out, which could be a problem on some projects and products like Dampstop have been formulated to help reduce those times significantly.
Again mechanical means of preparation is the best and we do not recommend that you use Acid etching as a means of preparation, this has not been used by the majority of the trade contractors for thirty years. It is messy, dangerous and ineffective.
It actually states in the British Standard BS8204-6, "surface preparation by acid etching of the concrete should not be used because of the associated health and safety implications and because the concrete surface is left saturated with water and calcareous salts which may ultimately lead to debonding or osmotic blistering of the resin flooring system."
There are various ways of preparing a floor here are some examples:
The method of Vacuum shotblasting involves steel abrasive (shot) being propelled at high velocity by a rotating wheel within the machine body, and then onto the designated surface to produce the desired profile. The debris is collected in a vacuum unit for disposal, and the shot is recycled for continued use. You would select vacuum shotblasting to:
- Produce a profile for the application of resin flooring.
- Remove paints and sealants.
- Create adhesion for the application of a wide range of surface finishes.
- Prepare steel (Commercial and Swedish Standard SA2 ½). prior to painting
- Remove laitance from concrete floors prior to coating.
The type and size of the machine selected will determine production rates achievable and degree of profiling required for the specified material to be applied.
Concrete is a well used term and understood by everybody, unfortunately the term "Concrete" covers a multitude of mix designs for a whole host of different real world situations. A concrete floor should be at least 25N/mm2 if a Vacuum Shotblast is to be used, if not the process can remove an excessive amount of substrate leaving a surface that will need remedial work prior to painting. In fact most Vacuum Shotblasting will leave "tram lines" in the substrate that are likely to be visible in the finish after painting, these will be highlighted further in gloss finishes.
These can be avoided by either
1. Grinding after the Vacuum Shotblasting to remove the lines.
2. Apply a system thick enough to cover the profile, this is normally achieved by an initial "scratch coat" primer which is a primer like Reprotec Supaseal
mixed with around 45 - 55 % dried sand (e.g. Kiln Dried Block sand) scratched across the floor using a floor trowel.
This is then usually fully blinded with the same sand and swept of when cured, usually the day after, this gives a fantastic key for the following coats.
Vacuum Shotblasting is a specialist operation and should be carried out by competent specialists.
For the factory manager looking to utilise his own staff the following method is relatively simple to carry out by the non specialist and is highly effective.
The grinding process is provided by diamond, tungsten or resin bonded discs or plates which are secured to single or multiple heads and rotate in a circular motion. Selection of the correct diamond or resin bonded plate is essential to achieve the correct combination for smoothing, preparing, polishing or cleaning. Grinding machines are designed for wet or dry operation and to tackle a wide variety of applications from fast grinding on uneven or tough surfaces to producing highly polished finishes, such as resin terrazzos. The type and size of the machine selected will determine
achievable production rates in terms of area, speed and the degree of profiling required for the specified material to be applied. All grinding machines should be designed to be used with dust extraction.
- Metal bonded discs/plates for general grinding operations.
- Resin bonded diamond accessories for polishing operations.
- Polycrystalline Diamond discs (PCD) for removal of adhesives and elastomeric systems
There are a number of outlets that will provide the equipment and advice on how to use it.