The countertop mix varies from project to project depending on type of finish. But yes, its sand, cement, and aggregates, and water that makes concrete. As far as concerns for moisture there are several types of sealers on the market that will help with the moisture. Along with a sealer, I recommend polishing the countertop with a furniture polish, such as lemon pledge. When it comes to scratches, the concrete countertop should treated with the same care as any other countertop in your home.