Frequently Asked Questions
We have compiled a list of some of the most commonly asked concrete related questions. If your question is not listed below, you may contact us using the form on the right of this page.
The process of polishing concrete with a concrete floor grinder is similar to refinishing wood with a floor sander. Concrete grinders are used to gradually grind down the concrete surface using a combination of metal bond diamond abrasives followed by resin bond diamond abrasives to achieve the desired shine and smoothness. Watch a video on how to polish concrete
Traditionally concrete should cure for 28 days prior to polishing. This time allows the cement and water to harden and bind the aggregates into a rocklike mass.
Recommendations for polishable concrete:
1. Minimum concrete compressive strength of 23 MPa (3500 psi).
2. Normal weight concrete and no lightweight aggregate.
3. Preferrable non-air entrained. (Still can be successfully polished).
4. Flatness requirements: ASTM International E-1155
5. Tight hard troweled (three passes) concrete.
6. No burn marks
7. Curing options (ASTM International C-309, C-171) - no acrylic curing and sealing compound
8. Admixtures may be used
The price of polished concrete can range depending on the condition of the concrete slab and the desired level of polish. Prices can range between $3.00USD per sq foot to $12USD dollars per sq foot
A wavy floor can be polished running your WerkMaster Machine in Ultra-Flex Mode. Ultra-Flex Mode allows your machine to follow the contours of your floor while it polishes. Watch a video about Ultra-Flex Mode
There are two main options for a mechanically polished concrete. Option 1 is referred to salt & pepper finish. Option 2 is referred to full exposure
The choice of machine to use can vary based on several factors. Size of the job and availability to power can greatly influence your choice of machine. Download WerkMaster Machine Comparison Guide
The time required to grind or polish a concrete floor can vary on job site conditions, type of concrete(hard or soft), desired exposure(salt & pepper or fully exposed aggregate) and experience of the operator
Diamond Abrasive life will vary from concrete slab to concrete slab. Please visit our WerkMaster Machine Specific Diamond Abrasive Tooling Guide page for more information on diamond abrasive wear information
Using metal bond diamond abrasives with Grits ranging from 16Grit to 50Grit, Pad speed should range from 500-700RPM.
Using metal bond diamond abrasives with Grits ranging from 80Grit to 150Grit, Pad speed should range from 700-1200RPM.
Using Resin bond diamond abrasives with Grits ranging from 30Grit to 100 Grit, Pad speed should range from 500 to 900RPM.
Using Resin bond diamond abrasives with Grits ranging from 200Grit to 400 Grit, Pad speed should range from 700 to 1000RPM.
Using Resin bond diamond abrasives with Grits ranging from 800Grit to 3000 Grit, Pad speed should range from 1100 to 2000RPM.
Densification is an important part of polishing concrete. Applying a densifier(liquid chemical hardener) to the concrete will solidify and densify the surface and provide extra protection from water penetration and staining. Densified concrete hardens the surface of the concrete and produces a higher sheen polish. Densifier is traditionally applied at the 100Grit resin stage after the floor has been exposed and metal tooling marks removed. To learn more, visit our densifier page.
Tooling marks can be caused by grinding an uneven floor. In attempt to flatten the floor the tooling can catch an edge or ridge in the floor and create a deep scratch. Tooling marks can also form when to low of a grit diamond abrasive is used in your initial cut(s) on a soft concrete floor. To determine whether your concrete slab is hard or soft please visit our MOHS Concrete Hardness Testing
Coatings can be removed using specific diamond abrasives. To learn which type will work under your WerkMaster Machine, please visit our Machine Specific Diamond Abrasives Page
Filling cracks in holes in concrete is recommended to improve on the visual aesthetic of the concrete slab. There are many cementitious patch products on the market that can accomplish this. For filling small holes we recommned using GM3000. learn more about filling small holes in concrete using GM3000
First, Check that the diamond abrasive not worn out. If that is not the case the most probable cause is that the diamond abrasive tool has glazed (not been dressed by the concrete surface. To deglazed or expose the diamond abrasive you can try:
Reduce the pad speed of your machine to 500 - 650 RPM
TIP: Try misting the floor with water(to soften the concrete surface and allow the diamonds to cut into the floor deeper)
Switch your tooling position on your machine. Move the out side tooling to the inside and vice versa
TIP: Try running your machine on a patio paver or rough concrete to expose and refracture the diamonds
TIP: Try broadcasting sand over the surface in an attempt do dress the glazed tooling
In metal bond tooling the diamond abrasive is suspended in a matrix of metals like aluminum, magnesium, or titanium. In resin bond tooling the diamond abrasive is suspended in a matrix of a ceramic or organic compound.