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The Grinding & Polishing Process.   
 
Polished concrete is produced by removing the top surface laitance and grinding down to the centre of the first layer of aggregate then polishing to the degree of shine required.  
 
Wet or dry grinding/polishing methods can be used. Dry grinding is a cleaner process when the equipment is connected to a suitable dust collector. Wet grinding extends the life of the diamond but creates slurry that must be collected and disposed of carefully by using an industrial vacuum with wet/dry capability such as the M450.  
 
The Preparation Group recommends Terrco® Multi-head Grinding and Polishing machines, a system that produces fast, precise results and a strong, durable high luster floor. There are four machines in the range depending on the project size, including the newly launched Terrco®701-S, easy to transport and designed for areas under 500m2.     
 
Diamond Cutting Heads
Diamond grinding and polishing head technology can be quite confusing. As a general rule hard composition surfaces will require a soft bond diamond segment and soft compositions a hard bond. The correct diamond accessory is important, as incorrect selection will either simply glaze over and not grind the surface or will ‘wear out’ extremely quickly. Resin-bonded diamonds are preferred for polishing.  
 
Working up through the grades
Metal bonded diamond-segments are attached to the Terrco® Grinding machine with the operator progressing from coarse to fine diamond grits. Each concrete floor presents different conditions and challenges but a typical first step is to grind using a coarse metal-bonded diamond segment. This will remove stock to the finished floor level, maximise the area of exposed aggregate and minimise areas of the less attractive and less hard-wearing sand and cement mix.
 
This first grinding process is vital to achieving a successful final result. Often, this stage can take more than 50% of the time to complete the project even though a further eight stages may be required.  
 
The resulting coarse surface is then ground with the same equipment, but this time fitted with the next segment. This will remove approximately half the profile (peaks) that remain and the process then continues using finer diamond segments until the desired surface is reached. Each stage of the grinding process must be completed carefully and thoroughly. Any ‘cut corners’ or missed areas will not become apparent until much later when scratches, which should have been removed earlier, will suddenly become very obvious and be time consuming to remedy.  Each stage also requires the use of a hand grinder, to complete the edges and corners. Any lines or surface differences can then be ‘faded out’ during the proceeding multi-head grinding operation.  
 
Adding a chemical hardener
After completing the grinding process, and prior to the polishing stages, a chemical hardener or densifier can be applied. The timing of this depends on the composition of the concrete. The densifier bonds the surface, provides extra protection from contaminant penetration and produces a better polish. It reacts with the calcium hydroxide in the concrete to form a hard, crystalline structure. It is essential that the last grind prior to applying the densifier is scratch free, as the resulting hardened surface makes removing scratches much more time consuming. The final polish can use up to a 10,000grit segment, which will leave a mirror finish. This finish is ideal for locations where the floor will remain dry, but is not recommended if the floor may become wet as it could create a slip hazard.  Edgework can be polished using a tool such as PPC’s Variable Speed 5’’ Wet Polisher which offers complete control.   
 
The result?  A strong, durable, high luster floor.
 
After the polishing process is complete, the only maintenance required is light cleaning using a diamond impregnated pad such as Storm Diamond Pads and water.
 
For help and advice on selecting diamonds call The Preparation Group on 01522 561460 or contact us