Lightweight carvable cement mixtures are ideal for making outdoor sculptures, stepping stones or other pieces of artwork. Although carvable cement, often called ferrocement, weathers faster than typical concrete, it will still last for many years. Working conditions for carvable cement can be difficult to pin down. Exposure to long periods of sunlight will cause rapid drying, while rain can cause a carved piece to slump into a big mess. Working with lightweight carvable cement takes time and practice, but can result in long-lasting pieces of artwork.
Mix one part Portland cement with three parts builder's sand in a wheelbarrow to create a lightweight, carvable cement mixture. Add powdered concrete tint at this time, if your design calls for it, and combine the dry ingredients with a hoe.
Add water to the mixture, stirring regularly with the hoe to make a slurry mixture the consistency of pudding. Add the water slowly, as large amounts of water can overpower the dry ingredients, causing the mixture to become too fluid. Should you add too much water, add a small amount of Portland cement to re-thicken the mixture.
Spray a prepared concrete mold with spray mold release and pour the cement mixture into it. Tap the sides of the mold regularly to disperse small air bubbles from the cement mixture.
Keep the cement-filled concrete form at a temperature between 72 and 82 degrees and allow it to rest for 3 hours. Colder temperatures will require longer drying times, while warmer temperatures will take less time.
Remove the mold from the cement when the mix will firmly hold its shape. Carve the piece using your hands as well as knives, spoons and any other wood or metal tools you find useful for your purposes. The cement will continue to harden as it is exposed to air, so keep at your work until you've completed your project.