Diamond is used in abrasive products because it is the hardest material there is.

Diamond abrasives are made by mixing synthetic diamond grit with a binding agent of metal or resin.

The resulting products are called metal bond or resin bond diamond segments.

This photo shows the metal bond diamond segments suitable for use on the disc shown above.

The smoothness of the surface finish on the floor is determined by how fine or coarse the diamond grit is.

A small grit size will produce a finer scratch pattern and increase the life of the segment.

A large grit size will have the opposite effect.

The life of the segment is also controlled by the hardness of the bond.

A hard bond will take longer to wear away and expose more diamond grit, where a softer bond will wear away more quickly.

A hard bond also produces a finer scratch pattern in dry grinding.

The number of diamond segments under the machine will also have an effect on the surface finish.

Increasing the number of segments will reduce the amount of work each segment has to do and create a smoother scratch pattern.

It also reduces the load on the machine.

Another technique used to increase efficiency is to put extra abrasive material onto the floor, such as sand or silicone carbide.

Selecting the right tooling

The rule of thumb for selecting the right diamond segment for a particular slab is:

      If the concrete is hard - use a soft bond segment

      If the concrete is soft - use a hard bond segment.

This rule applies in general because hard concrete tends to produce fine, powdery dust, which is not very abrasive.

As a result, it doesn't help to wear down the binding material in the segment and expose new diamonds to perform the cutting action.

In some cases, if the bond is too hard, the segment may stop grinding altogether and start to glaze over as it overheats.

So you need to use softer bond that will open up more easily to keep the diamond grit working.

By contrast, if the concrete is soft and producing a much coarser dust, the dust will have an abrasive effect on the segment and wear it down faster.

In this instance, you should use a segment with a harder bond to avoid going through the material too quickly.

How do you know how hard or soft the concrete is before you start?

In general, the higher the compressive strength of the concrete, the harder it will be.

Compressive strength is measured in megapascals (MPa) and is specified when concrete is ordered from the supplier.

However, given the fact that the grinding process normally only deals with the surface layers (often the top 5 mm or so), the surface condition of the concrete is often far more important than its compressive strength.

For example, a highly burnished surface, caused by over-trowelling of the wet concrete, can make the surface very smooth and behave like hard concrete.

On the other hand, a rain-damaged or shot blasted surface will produce more gritty, sandy dust, and so behave more like soft concrete.

In the end, the best way to select the right tooling for a particular slab is to look up the table supplied by the manufacturer and make an educated guess, based on the type of material you're removing and the manufacturer's suggestions.

Then you should see how the segments go, and inspect them regularly while you're working.

You may need to change the segments if they are wearing too quickly or not wearing enough.

For more information on diamond tooling and hints on how to select the right tooling for the job, go to the Floorex website and download: 'What is diamond grinding?'