The most common reason to harden pea gravel is for decorative walkways. Pea gravel usually has smooth edges and if laid on the ground in a loose fashion, it will quickly spread all over your yard. You can prevent this by using the pea gravel as the coarse aggregate in your concrete mix. This will prevent your pea gravel from becoming an eyesore or tripping hazard around your yard.
Purchase a decorative walkway mold or create a mold or form to pour your concrete mix into. You can get decorative molds at most home improvement locations where you would purchase concrete mix and pea gravel.
Mix concrete powder and sand into a container like a 5-gallon bucket. Every brand of concrete mix requires a specific mixture of sand and concrete powder. Use the appropriate mixture outlined on the concrete label.
Wet the concrete mix with the appropriate amount of water. Use the amount of water listed on the label of the concrete powder bag.
Pour the concrete into the mold and level it out with a trowel.
Place the pea gravel on top of the concrete mix and level it out with the trowel. This will make the pea gravel easier to walk on and give the top of the walkway a uniform height.
Spread sand over the surface of the concrete and pea gravel. Allow the walkway one hour of drying time and sweep the excess sand off the walkway with a broom.