How Long Should You Allow Concrete To Cure Before Grinding?

2020-10-26

Just about any concrete floor that is structurally sound can withstand polishing. Yet there are a few exceptions that need to be considered:

Before grinding concrete that is new, the concrete needs to cure to a hardness that is sufficient. This typically takes between 14 to 28 days after the placement of the concrete. An existing floor that requires extensive patching and floors that are extremely porous and soft might not be the best candidates for grinding or polishing. To get more information; It is possible to test the hardness of the floors in various spots when using a coin or screwdriver to abrade or scrape the surfaces. For surfaces that are badly spalled, the concretes surface layer might need to be removed with the use of a scarifier.

Steps Involved In The Polishing Process:

1. Identify The Condition Of The Concrete

If you are planning to polish existing concrete, the first part of the process involves evaluating the surface on the concrete. Here are a few things to look out for:

Low or high spots

Blemishes and minor cracks

Spalling at the joints

Existing epoxy coatings, paint or sealers

Mastics or adhesives that remain after removing the floor coverings

The majority of the surface imperfections that are minor and coatings are easy to remove with diamond grinding. However, if the floor displays joint spalling and major cracks, other types of remedial methods are required.

2. Prepare The Surface

The initial step for polishing concrete involves removing existing coatings and sealers. If the concrete is new or only features a light coating or minor blemishes you can begin with the first part of rough grinding.

For thick urethanes, epoxies, mastics or membranes, it is recommended to repeat the process over the surfaces using a coarse 16 or 20 grit diamond tooling that is made for removing heavy mastics and coatings.

From here you can fill control joints and cracks present in the flooring with a semi-rigid joint-filler or epoxy. You need to ensure the filler is level to the surface which will help the polishing-heads to easily move over the surfaces of the floor.

3. Start Polishing

The surfaces are now ready for rough grinding, which prepares the floors for a final smoothing. This typically involves a 3 to 4 step process, dependent on the overall condition of your concrete.

In the majority of cases, you should begin with a 40-grit coarse diamond-segment that is bonded into a metallic-matrix. After passing over the surfaces a few times using the 40-grit, change to a finer 80-grit and then a 150-grit metal-bonded abrasives to repeat these processes.

Each of the diamond-grit steps will require at least 2 passes, depending on how dense the concrete is. If you are polishing a newly cured concrete floor that is blemish free, level and clean you can start your polishing process using an 80 or a 150 grit.

4. Densify The Concrete

Once you have completed the coarse grinding, it is always helpful to apply a chemical liquid hardener to help densify and solidify the surfaces. This also adds an additional protection from staining and water penetration.

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