During home renovations a concrete grinder can remove glue from carpeted or tiled floors, it can level uneven slabs, create a new aggregate look, prepare a floor for the application of sealers or paint, clean up spilt concrete, plaster or other materials on floors, polish concrete and remove old paints.
Before selecting which concrete grinder will suit your needs the most appropriately you will need to understand how diamonds work to cut the concrete because if you choose the wrong type it will not produce the results you would expect. Many people have begun with a concrete grinder working very productively only to find after an hour that they have slowed down to a snail’s pace. All modern concrete grinders use diamonds now as the abrasive, but there are a few things to consider.
The diamond segments used on grinding plates of concrete grinders are metal blocks containing embedded diamonds which are only exposed as the concrete sands wear away the metal. If the diamonds are not exposed they will not cut the concrete and this is what happens when the segment metal is too hard for the particular hardness of the concrete. For hard concrete the diamond segment metal needs to be softer so that the small amount of sand the comes from hard concrete will wear away the metal sufficiently to keep exposing the diamonds, while for soft concrete the metal needs to be harder to prevent the large quantity of sands produced from wearing away the metal too quickly. Diamond grinding wheels usually come in three metal types – soft, medium and hard.
If you use a medium metal hardness segmented diamond wheel on very hard concrete the diamonds will eventually blunt and break as they do continuously, but the metal surrounding them will not be worn away fast enough causing the metal segments to become polished. When this happens the grinding wheel will get very hot and will not grind away the concrete at all.
The first tip is to select the correct diamond segment hardness to suit the hardness of your concrete floors so that your concrete grinder will work productively. When removing glue or paint from concrete floors the diamonds cut through the material and into the floor underneath so it is essential that the diamond segments match the floor hardness. Work the concrete grinder in circles if possible or from side to side taking bites into the glue or paint with each movement. This is the best way to remove it because if you push the concrete grinder into the middle of the paint or glue it will only smear the material as it heats up and you will strain the grinder motor unnecessarily as it struggles in the sticky contaminant.
Another consideration is the grade or size of the diamonds used which are expressed as grit sizes. Use a coarse 20-40 grit for paint and glue removal as well as for heavy concrete removal, use a 40-80 grit for a finer finish on the floor where the scratches are not seen easily and use a 80-120 grit for a very fine finish. For a polished floor or benchtop the grit size must be 3000-5000.
To level slabs where one has moved, start from the highest point and grind it away until it reaches the lowest point of the other slab grinding back away from the high point to flatten the floor. Use a metal straight edge approximately the height of a person to check the levels visually and use the concrete grinder to grind down all the high areas until the floor is to the level that you need. A concrete grinder can be used to create new levels for drainage, but this is usually slow and difficult work as the grinder has to cut away the hard stone aggregated used in the concrete mix that is below the surface of concrete.
A concrete grinder can be the fastest way to clean up a floor after other work has been completed. It will quickly remove spilt mortar, plaster, paint splashes and other materials that have been walked onto the floor and prepare it for whatever covering will be used later. The benefits of preparing a floor this way include leveling the small high spots to reduce the amount of mortar used when tiling or to provide a flatter floor when laying vinyl, and to open the surface so that sealers and glues will adhere strongly and permanently.
To achieved polished concrete a special type of concrete grinder is normally required that has a planetary action head where three or four heads touch the floor and rotate in one direction and the turntable that contains the heads rotates in the opposite direction. It is easier to achieve a flat floor with this equipment, or alternatively one of the eight headed machines that has four heads rotating clockwise and four rotating anticlockwise.
The process is to grind with grits that double in number for each subsequent pass. Start at 30 grit, then 60 grit, then 120 grit until you have reached 3,000 grit. After 120 grit you change from metal bond diamonds to resin bond diamonds and after the first pass at 30 grit you need to spray the floor with some adhesive before passing over with 60 grit to fill the minute airholes that will appear in the floor. Between 60 and 120 grit you will also need to harden and densify the floor using a chemical hardener which will make it easier to achieve a high gloss and to maintain it. diamond painting