An easy way to make a garden path or informal walkway is to simply dump dry concrete on the ground and water it with a water hose. There are a few tricks to making it look good, but it really is a pretty easy way to make a path through the backyard. Wear old clothes because concrete work is pretty messy.
Defining the Path
The first step is to lay out the path. An easy way is to take a garden tiller and plow up the outline of your path. Scrape out the loose dirt to a depth of two to three inches below the surrounding dirt. Carry off the dirt in a wheelbarrow, or scrape it out away from the shallow trench you've made for the walk. You don't need forms for this type of path.
Lining the Trench
Get yourself some of that black or green weed-blocking fabric they make for flower beds. It lets water through, which is important as the walk sets up. Use it to line the bottom of the pathway trench. Use nails or large staples pushed through the fabric into the dirt to hold down the fabric while filling the trench.
Laying the Base
If you want to lay some flat rocks in the path for interest or to strengthen the walkway, place them in the bottom of the trench. You will pour the dry concrete around them to fix them in place. To increase the durability of the pathway and reduce cracking and settling, lay lengths of thin reinforcing rods in the bottom of the trench. The rods work with the gravel aggregate in the concrete mix to strengthen the concrete and help prevent cracking.
Pour the Concrete
Buy bags of concrete designed for building retaining walls by stacking the bags and pouring water over them. You can also use quick-drying concrete mix. Be sure to wear gloves and a mask. Break open the bags and pour the dry concrete directly into the trench and fill the trench to the top. It should be at least two inches deep. Carefully tamp down the dry concrete mix and rake it smooth on top.
Wetting Down the Path
Get a nozzle for your garden hose that can be set to do a fine mist. Use the mister to gently dampen the dry concrete. Slowly wet it down thoroughly. Water should start to puddle on the surface, and the concrete will darken and be wet through.
Sand the Surface
Once you've wet down the concrete thoroughly, sprinkle brick sand over the surface of the path. Broadcast the sand so that you cover the surface lightly but evenly. If you're happy with the look of the pathway, leave it to set overnight, then dust the surface again with loose sand. If the surface is pitted with water spots or you'd like a smoother look, let the concrete firm up for an hour or so and then, while it's still dark and damp to the touch, sweep the surface with a garage broom or even a kitchen broom with stiff bristles. The broom will leave texture lines, so be careful to brush in roughly the same direction throughout–either lengthwise or crosswise. Let the path cure for 24 hours before walking on it.