The interior concrete floors have cured long enough that they are ready for polishing. A heavy machine fitted with diamond tipped blades (reminds me of an electric shaving razor) makes several passes over the concrete surface. Its job is to remove the “cream,” the uppermost 1/8 of an inch or so of cement that forms the skin of the cured concrete.
Removing the cream exposes the pea gravel aggregate which gives the finished surface a lovely “salt and pepper” appearance. The trick is to remove just enough to expose the aggregate without overdoing it so that the salt and pepper look gets too chunky.
Once the removal step is complete, polishing begins with successively finer grit, just like sanding a piece of wood. The final grit for this project is 400, which we feel is not too shiny but still lets you see into the depth of the concrete, so to speak. Before polishing the main floor, the contractor did a test patch to the satisfaction of architect and homeowner so everyone agreed on the look we were targeting.
As part of the polishing, a densifier is added to essentially fill in the pores of the concrete so it is resistant to water and stains. The polished floor was then covered with protection boards for the duration of construction. Just before turning the finished house over to the homeowners, the protection will be removed and one last densifier coat will be applied. They will look gorgeous!