It's all done now. The office will be put back together later today.
The portion to the left, in the fourth photo, was much higher originally. When it was ground down, this exposed the larger rock below.
My friend wasn't concerned with having an absolutely new looking floor. He realized he's working with 100 year old concrete.
Although it was a hard slog, this method of finishing a concrete floor, uses far less resources than any other method that I know of. We used one gallon of
water soluble finish and we used so little of the diamond disc that they didn't charge for it.
Two days after the grinding process, I still had sore pectoral and abdominal muscles.
Fini