A masonry grinder is a tool for grinding cement block, brick or concrete floors. There are several types of masonry grinders. Some are actually hand-held with a handle and operated with old-fashioned back work. Some are electric. Some run off of small gasoline engines.
Use a hand-held masonry grinder if you have a strong back and a lot of willpower. These are slow in grinding. You must use them in a circular motion. They have a hardened masonry bottom which is rough. This rough bottom is what grinds the concrete or cement that you're working on.
Consider the use of an electric masonry grinder. This grinder cuts fast and throws an awful lot of masonry dust. It's best to use a safety mask and eye protection when working with this type of masonry grinder. This grinder normally uses a full carbide blade. But some electric masonry grinders have diamond tip blades.
Know that a gasoline powered masonry grinder is often used on grinding concrete floors or driveways. This grinder operates with grinding wheels which rotate slowly. Water is applied to enable the masonry grinder to cut faster and not generate too much heat on the grinding wheels. This causes the grinding wheels to last longer.
Use a slow, even motion back and forth (left-to-right and right-to-left) in a half-moon fashion when you use a gasoline powered masonry grinder. This type of grinder makes the concrete very slick, much like glass. Be cautious when walking on these floors after you finish grinding.