An aggregate patio is a concrete surface that has had the outer layer of cement paste removed to show the course aggregate beneath. Its skid resistance and durability make aggregate a practical choice for a patio, but if you don't like the appearance, you can install pavers over it. Laying pavers over the surface re-purposes the aggregate as a strong foundation.
Clean the aggregate surface of debris with a scrub brush and mild laundry detergent. If you see any grease stains, scrub them with a concrete stain remover. Hose off all soap and stain remover and let the surface dry.
Dry-lay your pavers over a section of the aggregate to practice the pattern you want to use, allowing a 1/2-inch of space in between each paver.
Mix four parts sand and one part cement with water until the mixture is stiff, not soupy.
Spread 1 inch of sand mortar over the aggregate with a trowel, enough to lay four pavers at a time.
Place the pavers into the mortar following your pattern and spaced ½-inch apart. Level the pavers using the handle of the trowel, and press them ½-inch into the mortar. Remove excess mortar and spatters from the pavers as you go using the trowel or a clean, moist cloth. Let the pavers set in the mortar for two days.
Mix grout in a bucket with one part sand, one part cement and a small amount of water so it is stiffer than the sand mortar.
Pack the grout between the pavers with the edge of the trowel, removing excess as you work. Use a concave jointing tool between the joints to make the surface smooth and neat.