We have the potential to get several car washes who all have concrete, after the cars leave the wash area they are still dripping water so the combination of water dripping and the rubber from the tires and the water based tire shine leaves the concrete looking black. The owner said he had it cleaned in 2008 which i doubt because I live a block from his store, but he might have had one of the guy use a portable unit to try and clean the surface. Problem is he said sure you can come in and clean an area and it it stays clean for a while( he would say for how long) then you can clean the rest of the area its 15,000 sq ft. I want to put him on a quartely cleaning schedule but the other thought it to apply something to help seal the concrete and then it would be slipperly and with all the walking thats being done it would probally wear off and have a bigger mess. Anyone doing commerical car washes where they have concrete and how often do you clean them and is it even practical to try and put a sealer on the concrete or just tell him his concrete will last longer if we keep it clean it on a regular basis.