Concrete grinding has become a popular activity in construction projects. But what exactly is it and how is concrete actually ground?
In the following section, we discuss the importance of grinding, what it entails, the tools used, safety precautions and everything else you may want to know about the process.
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What is Concrete Grinding?
Concrete grinding is the process of removing ridges, contaminants, and loose material from the subfloor surface using a special grinding machine. [expand title=”READ MORE”]
By removing the imperfections, you can lessen the overall cost in preparing the floor prior to covering. Plus, if you can achieve a smooth enough grind to allow carpet or vinyl to be laid on top, you won’t need to apply a cement-based skim coat. In addition, you can forego of the waiting time needed for the skim coat to dry.[/expand]
Types of Grinders
Grinders come in a variety of types and sizes. The choice you make will depend on the size of the job and the type of material you need to remove.
In corners and tight areas, hand held grinders should be used. These specialised grinders, unlike ordinary angle grinders, have a dust shroud and extraction hose. The user should utilise these attachments when there is a lot of dust being generated. [expand title=”READ MORE”]
For the main areas of the floor, walk-behind grinders are preferable. These grinders are driven by mains electricity – mostly 240 volts or sometimes 3-phase power. However, diesel, LP gas, petrol, and compressed air are sometimes used as fuel.
Grinders can have single, double, or planetary head action. There are even four-head grinders commonly used in large projects.
Single head grinders
A single head grinder has a central shaft that drives just one head. In smaller grinders, the head usually contains one disc measuring 250mm in diameter.
Larger machines can have multiple discs within the same head, some containing up to six discs with varying diameters. In machines with six discs, the diameter of each disc might even be smaller.
With so many discs working on the concrete surface, these grinders produce a very fine finish which explains why they’re mostly used in polishing rather than grinding.
Single-head grinders have a grinding width of approximately 550mm.
Double-head grinders have two heads each capable of holding one or more discs. In some machines, the two headers rotate in the same direction.
This usually causes the machine to pull to one side which can make it difficult to pull across the floor. But you can at the same time take advantage of this characteristic when working on walls.
In other machines, the heads rotate in opposite directions to balance the torque and increase machine manoeuvrability. Double head grinders have a grinding width of between 750mm and 1,000mm.
Planetary action grinds
In planetary header grinds, the header moves like a “planet” – independent of the grinding discs (or satellites) mounted onto it.
Planetary grinders are excellent surface preparation tools. The planetary head and the disc rotate in one direction which has the effect of increasing speed.
This usually results in more aggressive cuts especially where the diamonds (more on this shortly) are located closer to the outside of the head.
Planetary grinders, thanks to their aggressive grinding, can also be used in concrete surface polishing. To achieve clean polishes, the discs are set to rotate counter-clockwise.
For concrete grinding, however, the discs must never be set to rotate counter-clockwise.
Ultimately, the tool that usually comes into contact with the concrete surface is a set of diamond abrasives. Diamond is used because it is the hardest material on earth.
The abrasives are made by mixing synthetic diamond grit with a binding agent of metal or resin to create what is called a metal bond or a resin bond diamond segment. [expand title=”READ MORE”]
The smoothness of the grinding is determined by the fineness or coarseness of the diamond grits. Smaller grit sizes will produce a finer scratch pattern, increasing the life of the segment. Larger grit sizes, on the other hand, produce a rougher scratch pattern
The life of the segment is also dependent on the strength of the bond. Hard bonds typically take longer to wear and expose the diamond grit. A softer surface, on the other hand, tends to wear away quickly.
The number of diamond segments found on each grinder header will also determine the quality of the finish. Where there are many grinders on the same header, the result is usually smoother.
Moreover, with a higher number of headers, the amount of work for each segment is reduced. This also reduces the load on the grinding machines.
For a finer finish, you can put some extra abrasive material such as sand or silicon carbide on the floor you’re working on. [/expand]
Safety in Concrete Grinding
Like most machines, concrete grinders are only safe if you use them correctly. This means you need to follow the manufacturer’s guide at all times. [expand title=”READ MORE”]
A few things to keep in mind include; before you start
Familiarise yourself with the equipment. Make sure you know how it works.
Check to ensure that the environment is safe. The place should be well lit, clear of clutter, and dry to avoid electric short circuits.
When setting up the machine
Wear appropriate safety gear. Don’t wear loose clothes that could be caught in the moving parts and wear closed boots.
You may also need gloves, safety glasses, and a hard hat depending on the job conditions.
When operating the machine
Listen for any strange noise or unusual vibrations. If something doesn’t feel right, turn off the machine immediately and troubleshoot the problem.
Maintain balance throughout the grinding process, with your hands firmly gripping the machine. Avoid awkward angles.
Your hands and feet must be kept away from moving parts at all times.
Turning the machine off
Once you’re done, unplug the machine. For diesel o petrol powered machines, turn off the fuel line.
Inspect the machine for any damage before putting it away.
As you can see, the grinding process isn’t all bread and butter. You need the right tools and the right techniques for best results.
Megasaw can help you acquire the best machine and tools for the job. Contact us today to learn about the different grinders, diamond tools, grit sizes, and anything related to diamond grinding services.