At BECOSAN® we are known for making concrete floors longer lasting, easier to clean and more beautiful. Key to our approach is grinding the concrete.
In this article we take you through what grinding means to us, what it is, why we do it, how we do it and, most importantly, what it costs.
What is concrete grinding?
Concrete grinding is using an abrasive tool composed of industrial diamonds on rough concrete surfaces to reveal a smooth finish.
Grinding concrete can be done either wet or dry. At BECOSAN®, we like to grind under wet conditions to reduce the amount of dust.
There are two types of machine we could use. The first is a traditional concrete grinder like the HTC 800-4A 800mm Automatic Self-Propelled Concrete Grinder, ideal for doing surface preparation. Then you can also use a power trowel, which is recommended to finish the floors. Power trowels can be hand held, like the Honda GX150 Power Trowel, or ride on, like the Wacker CRT36-26A 36in Ride-On Concrete Power Trowel.
The abrasive tool is a disc with an abrasive surface encrusted with industrial diamonds. Industrial diamonds are a commonly used diamond type in concrete grinding. These are available in different strength, shape, and size. The size of the diamond is represented in terms of grits.
The size of the diamond and the corresponding grit number are inversely proportional to each other. This means that a discs with larger diamonds has a smaller grit size and vice versa.
The rougher the floor, the lower the grit size. For polishing and smoothing applications, we use higher grits with small diamonds.
Hence, on a normal project we start with a low grit number and get progressively higher depending on the gloss level that the customer wants.
Why grind concrete?
A newly laid concrete floor will have a micro-rough surface. Before it can be put to use in an industrial of commercial setting it needs to be made smooth and sealed.
A smooth concrete floor produces less dust, will deteriorate more slowly and will be more attractive to look at.
Perhaps most importantly, from our perspective here at BECOSAN®, it must be done before we can apply BECOSAN® Densifier and Protective Sealer, the last step in our process.
Preparation before grinding
New concrete floors are the easiest to prepare – all we must do is wait while the floor cures. Normally for a well laid surface this would take about 28 days.
A used floor is a different matter. In an industrial or warehouse environment, a floor that has been used for some years will have suffered some damage. Bolts will have been left in the floor, cracks will have appeared and, possibly, fluids may have penetrated the surface. All of this must be fixed prior to grinding.
Wet or dry grinding?
There are two ways of grinding, wet and dry. With dry grinding no water is added to the grinding process and, hence, a lot of dust is created. To cope with this a vacuum cleaner is connected to the grinder to suck away the dust produced. All modern grinding machines are fitted with vacuum attachments.
Dry grinding is impractical on a large scale. Here at BECOSAN® we always grind using a wet grinding process. The floor is watered and the grinding is conducted using a power trowel. Wet grinding is more efficient and contains the dust at ground level. Of course, the grinding process generates a slurry of water and concrete dust which must be carefully removed.
Three types of finish
At BECOSAN® we have three standard grinding processes; Matt+, Semi Gloss and High Gloss. Each finish involves multiple grinding phases using progressively finer grades of diamonds. After each phase the floor has to be cleaned with a scrubber drier, like the Gmatic Rotan 195 BT 125, which collects the slurry produced by grinding and leaves the floor clean.
Half way through the grinding process we apply our proprietary densifier which chemically strengthens the concrete surface.
On completion of the grinding process we apply our own impregnating sealer which makes the floor more resistant to the absorption of liquids.
Finally, the floor is buffed up to leave an attractive shiny finish.
In summary the process for each finish can be described as follows:
- Matt+, Grit 50, 100, Densifier, 200, Sealer
- Semi gloss, Grit 50, 100, Densifier, 200, 400, Sealer
- High gloss, Grit 50, 100, 200, Densifier, 400, 1000, 3000, Sealer
Concrete dust slurry is a toxic, highly alkaline substance, which must be disposed of carefully. Often the difference between a truly professional concrete floor specialist and a cowboy is their attitude to slurry disposal. Here at BECOSAN® we take slurry disposal very seriously and utilise a three-step process.
Separate and neutralise
The slurry is taken away from the customer site and our BECOSAN® Separator is added to the mix. The Separator changes the PH balance of the slurry from a highly alkaline suspension to PH neutral.
The Separator also facilitates the separation of the reusable clean water from the mix which can be safely drained away leaving a non-alkaline condensed slurry.
The addition to the condensed slurry of BECOSAN® Solidifier changes the liquid slurry into a solid that can be more easily moved and disposed off.
The solid waste can now be safely taken away to an approved local government land fill site for disposal.
How much does concrete grinding cost?
A good question but a difficult one to answer as there are many factors that will affect the price.
Firstly, we must consider the quality, and in particular the hardness, of the existing concrete. A soft concrete is more difficult to grind as there are many issues that can occur. The floor being more abrasive meaning a higher amount in consumables will be used. So, the surface would need a good preparation prior to the BECOSAN® treatment.
Then we have to think about the degree of damage that the concrete floor has suffered. How many bolts are left in the floor and need removing? How many cracks have appeared? How badly marked is the floor with paint and tyre marks?
Also, we must consider the size of the floor? The bigger and wide open the floor is, the more efficient the grinding process can be.
Finally, the floors location is important. Is the floor very remote? Is it easy to get machines and slurry tankers in and out? Are local authority land fill sites available?
Given all these considerations we believe that, in 2019, the cost of producing a world class polished concrete floor that will endure for many years will be between 8€ and 25€ per meter squared.