A couple of years ago, the city decided to renovate some of the sidewalk on various blocks around here. For some reason, they chose the block that I live on to do it… and they practically had to put stickers around the blocks that they chose to refill, because people would insist on trying to sign their names in the concrete, walking in it or riding their bike right through it without a second thought. I doubt that concrete cleaner would have done them much good, though, given the circumstances. But it wouldn’t have hurt them to do something more about it. They might not have had to refill half of the sidewalk blocks around here if they had simply taken the time to clean it and take care of it before it got to the point where they had to excise separate blocks of it.