Yeah, sandpaper might work for just 4 sq feet but that's about it.

My project was about removing nasty water stains from my concrete patio and it took me about a year, working mostly several hours each weekend. The patio was done by a rather dishonest contractor one year in November just couple days before a storm that blew the blankets away and brought rain which then froze on the surface before the concrete had a chance to fully cure, leaving permanent dark stains. Now after the grinding the patio looks decent.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL