Concrete is comprised of cement, sand, gravel, and water. When these items get mixed together, they form a hard slab once it has cured. Unfortunately, during the curing process concrete often shrinks. This usually results in small, hairline cracks. So, now you have a cracked floor.
These smaller, hairline cracks are much easier to fix on your own than larger cracks. If a crack is too large, it is best to call someone to check it out. You want to make sure that there is not any other damage as well.
Smaller hairline fractures typically do not cause any sort of structural damage. However, they can become a point of entry for water, insects, etc. They are also something that most people can fix themselves.
There are several different products available to fix the crack in your floor. There are some products that only last a short while before you have to clean out the crack and start over, so it is best, as always, to do some research to select the best product for your needs.

These are the basic steps for repairing your cracked floor. There may be some variance depending on which product you choose for repairs.

Before beginning, check to see if the crack is dry. If it is damp, use a blow dryer to dry it out. Wait at least 15 minutes, then recheck the crack. If the cracked floor is still dry, you can proceed with repairs. If the crack is still wet, you will want to wait until it is dry.

Clean the Cracked Floor

The first step in fixing your cracked floor is to clean it out. You will want to scrub out any loose concrete, paint, or old filler. The best tool for this job would be a wire brush.
After you are done scrubbing, you want to finish removing the remaining dust and dirt. You can use a broom to get out the larger chunks and then a shop vacuum to clean up the finer dust. You want to get it all cleaned before continuing.

Mix your Product

Third, if you are using a product that needs to mixing, this is the time to mix. Make sure that you follow all directions when mixing products together. You should try mixing small amounts if necessary so that your product does not dry out while you are fixing the crack.

Apply your Product

Apply your sealant along the cracked floor as needed. Once your filler begins to dry, you will want to check and see if it is settling. If the product settles, you may need to add more to the crack. Once you have applied the necessary amount of product to fix your cracked floor, it is time to use a trowel to smooth the sealant along the crack.

Allow Cure Time

Again, each product will have different cure times. Do whatever the manufacturer recommends for the product you chose. Some may take just a few hours, and others may take longer. You may also want to allow for additional cure time if you had to apply the product thick.

Seal the Concrete

Once you take the time to repair the concrete, you will want to seal it as well. Because concrete easily absorbs stains, sealing it will help to prevent that from happening. If your crack was in a higher traffic area, you might want to apply several coats of sealant for more protection.