Break up the existing concrete patio into multiple pieces, using a sledgehammer. The size and number will be determined by the overall look you desire for the new patio. Remove them from the area.
Measure and mark the size of the new patio in the yard, using a measuring tape and stakes.
Dig out the expanded patio area, using the spade and wheelbarrow to remove excess dirt. Dig the new space to the same depth as the original patio. Use the level to maintain consistency.
Place two-by-fours along the sides of the newly dug out patio space. Using a hammer and nails, connect boards together at right angles to create a form for the concrete. The two-by-fours should be snug against the outside walls of the patio space. The tops of the boards should be level with the grass to keep the new concrete patio even with the surrounding yard.
Place the broken pieces of concrete inside the form with the smooth side up. Pieces should be level with the top of the forms to avoid low spots where water could puddle.
Mix aggregate concrete according to package directions in the wheelbarrow. Using the spade and the hand trowel, fill spaces between broken concrete pieces. Concrete should be spread evenly just to the top edge, but not over the broken concrete and tops of the form. Allow the concrete to dry for approximately 20 minutes.
Spray concrete retarder over the entire surface of the new concrete patio, using the low-pressure pump sprayer. Allow this to sit on the surface of the concrete for approximately six hours.
Turn the garden hose on and lightly begin spraying away the thin, filmy top layer of concrete from the aggregate underneath. As the thin layer of concrete peels away, the aggregate stones will be revealed. Spray only a small amount off the top to keep the patio level. Allow the entire surface to cure as recommended by package directions.
Remove the forms and backfill the edge of the patio with the dirt removed from the new patio area.