First, you need to do a test area starting with an orbital sander and 400 grit wet/sandpaper. Using water as lubricant- sand the test area. This should remove most of the top exposed surface. If all goes well with your test- then proceed to the rest of the floor. This can be done by a proficient handyman or floor refinisher.
Cement tiles' top color layer is extremely hard and can withstand this process many times in the life of the installation. There are floors over 100 years old that have taken much more of a beating. It is similar to being able to refinish hardwood floors. Most installers are fearful, and won't bear down on the sander to remove the top surface. They will only be removing a micro-layer.
WHILE DOING THE ABOVE REPAIR- YOU MUST CLEAN THE RESULTING SLURRY IMMEDIATELY. FAILURE TO DO THIS WHILE SANDING THE FLOOR WILL ALLOW THE GROUT TO STAIN.
Once you have successfully stripped the top surface, well enough- you MUST reseal with a sealant such as Miracle 511 Porous Plus.
The tiles need to be doused with water during the sanding process and wiped immediately with a towel." When we say "doused" you need to have enough water on the tile so they are saturated and no longer super absorbent. Here are some more details for the steps to help out with the process.
Function of the water -
The water serves 3 primary functions while you're sanding:
- It's saturating the tiles so they are no longer super absorbent, giving you a better chance of wiping the surface clean quickly.
- It's acting as a lubricant while you're sanding, more is better.
- The water is also diluting the resulting pigment slurry that is coming off the tile. think food coloring, one concentrated drop vs. one drop in a glass of water.
Have 2 buckets of water and 2 towels while you are working. One bucket of clean water to douse the tile before you sand and one bucket and towel for "dirty" water wiped up right after you sand a tile. A "wax on wax off" if you will.
Use the clean towel to douse the tile then sand with an orbital sander (one tile at a time) stop and wipe that tile with the "dirty" towel immediately.