1.FIRST CUT is the grinding of the required amount off the top to expose the aggregate; some want ‘salt and pepper’ with the aggregate partially exposed, or the customer may prefer a heavy exposure. The first cut is always done in several passes and at an even speed so no part of the floor is overground and forms an ‘ocean wave’. The first cut is done with coarse production grinding disc or tooling, 30-60mesh is common; 25 and 16mesh also is used to do the first part of the first cut. In practice the amount that is removed is often 2- 3mm and is removed in .5mm per pass. This means that if 3mm is removed, this will be done in 6 even passes to ensure flatness. So to quote a six pass floor properly, you need to quote on grinding 6 times the floor area. A shotblaster in the hands a skilled operator can drastically reduce both the cost and time to get just the top off the slab; especially if the slab is highly toweled (burnished).
2. SECOND CUT: Following the first cut it is best to do one thorough fine grind with 120-150mesh diamond discs to remove the all score marks from the coarser discs before you move into the polishing process. The important point here is that the phenolic polishing pads are not intended to remove score marks and wear fast on a coarse ground surface. Guide to quoting: So far in this example you have taken 7 even passes to do the job. If you charge at $8 per m2 for a single pass grind, this job is 7 passes x $8 per sq m = $56:00m2 for this stage.
Tip: know what it costs to grind each m2.
The Grouting Stage:
1. Wet the concrete to remove the suction fromn the surface, do this by simply brooming water evenly over the area and waiting until the surface goes from wet to damp.
2. Apply Grout-Plus to damp concrete floor using a soft bristled broom. Ensure an even spread of product. Approximate coverage is 25m2 per 5ltr, this may vary.
3. Using 120# metal bond diamonds, whilst the grout is still wet (immediately after application) run your grinder over the area on half speed. Do this until completely dry and all excess grout is removed.
4. Apply a Colloidal Silicate Hardener (Densi-Proof), this will harden the surface, and help to keep the grout from pulling out. Allow up to 24 hours before proceeding with the polishing stage.
Grouting Demonstration
The Polishing and Hardening Stage:
Following the First and second cut, the floor is ready for the polishing and Hardening stage. You will need to make an inspection at this point.
1. If the floor is very dense, with little or no porosity in the sand/cement matrix, then you may be best to start the polishing with 100mesh then 200mesh Resin Polishing Pads . Then apply a Colloidal Silicate Hardener (Densi-Proof), this will harden the surface, and help to ‘close’ the surface, and help create a sheen as you move further into the polishing process. (skip this step if already completed in the grouting stage) In the case of a particularly dense slab, polishing can come up well without any treatment, but usually won’t be as well ‘sealed’. If you apply the hardener to an already hard dense floor, it can make the initial polish slow and time consuming.
2. If the floor is porous and not really a hard matrix it may be better to apply a generous application of the Colloidal Silicate Hardener before you begin the polishing process. Now do the 50, 100 and the 200mesh passes with the Resin Polishing Pads.
*Hint - Ensure to thoroughly clean the floor in-between passes.
Now that you have completed polishing 50, 100 then 200mesh grades you may find that this is the time to apply the Colloidal Silicate Hardener (or another application, if you have already applied a coat before the 100mesh pads). Now you can do the 400mesh pads, and then the 800mesh. Many guys will at this point have a pump bottle or pressure garden sprayer with them while polishing while doing the 800mesh process (and finer grades) and spray a small amount of hardener on the surface as they go. This wetted surface helps to further close over the surface and develop the sheen. With 800mesh, you should have a nice ’60-70%’ sheen, and if you need/want to go further, the 1500mesh, 3000mesh and BUFF grades will give exceptional levels of sheen.
3. The final stage is to protect the concrete with Sealer Plus which is designed to repel water, oil etc and to stop staining.
*The above information is to be used as a guide only and Con-Treat accepts no responsibilty for any consequence resulting from the advice contained herein or verbally.
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