Crush the concrete slab into pieces and use it as gravel in a driveway, or use can also use it as the border around a vegetable or plant garden. The gravel will also look great in the bottom of a shallow fish pond. Just sprinkle across the bottom of the pond and it will really brighten up the pond when the sun shines on it.
Crushed Gravel also works wonderfully as flooring for an outdoor patio, or as a border around a swimming pool. Crushed gravel can also be poured into a hole before filling the hole with wet concrete. Simply fill up as much of the hole as you can with the crushed gravel, then pour concrete on top until the hole has been filled.
The different-sized shapes of the slabs will look great if you have a few different pieces. You can make a walkway going off of your porch or use them as steps through a flowerbed or garden. Concrete slabs also work perfectly when making a walking trail to a shed, or outdoor pavilion. Simply lay out a walking path, and place your concrete slabs down the trail, spacing them about six to eight inches apart.
If you enjoy using potted plants, place a few concrete slabs throughout your garden, and put the pot on top of the concrete slab for added height and texture.
Concrete slabs look fantastic when stacked on top of each other, so if you have five or six slabs, stack them beside your patio furniture to work as a simplistic end table. Try to stack them to about the height of the arm of your patio chairs. This will be a great conversation piece and is completely weatherproof. If you have large concrete slabs, you could also make an outdoor dining table.