Not all concrete is hard, or better put, not all concrete is strong. Sometimes the way a concrete floor is finished leaves it "soft" which is not a problem unless you want a decorative concrete floor. We ran into this on a job in Chapel Hill for a bouldering club. After we removed the VCT, we started to wet grind the floor. Once we had started, we noticed that the cement or the paste that held the floor together was soft in the extreme. The concrete in North Carolina is t