Mark Beamish Waterproofing had a unique task on our hands, as we joined into a $69 million dollar historic preservation of the Natural History Museum. Burnishing concrete that's more than a century old is a rare task for any contractor, especially in Southern California.

Over the two-year project, we polished roughly 70,000 sq. ft. of concrete. The floor’s surface showed visible cracks and color variations throughout years of different concrete grains and batches. We focused on cleaning up the concrete by grinding, polishing, and applying RetroPlate 99 hardener/densifier and RetroGuard sealer. We used RetroPlate because the museum preferred the concrete accurately represent its age. Retroplate simply represents what's underneath it, while creating a smooth finish to the floor. It was a very rough and uneven floor, and due to the age and hardness of the concrete, the first cut was very important.

Initially, we used 60/80 grit metal-bonded diamonds on a Klindex Expander 750 for the first concrete cut. We decided to change to 16/20 metal diamonds after realizing that the less aggressive diamonds didn't quite do the trick. 60/80-grit metals were utilized after the first cut, followed by 150-grit metals, which prepared the floor for polishing. After filing large cracks in the floor with epoxy, we used the Expander 750 to polish the floor.