I have removed old indoor/outdoor carpet from a cement porch. I have removed most of the glue but am having trouble removing all of it. I have used a metal scraper and also a floor sander. The glue is about 90% gone. The cement is smooth with the glue but it looks yucky. Also there are marks from where the glue was applied with the trowel. Like streaks on the cement. Any suggestions on how I can remove the remainder of the glue and the trowel marks?