The most common concrete surfaces are broomed concrete, exposed aggregate, stamped concrete and hard-trowel. Broomed concrete is most commonly used for city sidewalks and approaches. Exposed aggregate concrete is created when a cement surface is washed off with water after initial set. Advantage: its pretty. Disadvantage: the concrete has been aged 20-30 years immediately. Stamped concrete imitates natural surfaces such as stone, brick, slate, etc (see below). Hard-trowel concrete is generally used for garage floors and indoor surfaces. It has a smooth, shiny finish.