Marble dust can be mixed with various types of cement to form precast marble molded concrete. There are two types of cement that can be mixed with marble that will form a product that is hard and resilient: type S and Portland cement. The mixing methods, however, are the same. The average do-it-yourselfer can complete this procedure in one to two hours, depending on the size and scope of the project.
Add marble dust to a clean wheelbarrow. It is important that the wheelbarrow is clean in order to keep the marble color stable. Add eight shovels of marble dust to the wheelbarrow to begin with. You can add more after the mix is combined if you want to improve the marble content in the mix.
Add one-half bag of white Portland or type S mortar to the wheelbarrow. Wear a dust mask when adding the powder. The chemical contents of the cement will irritate the lungs. Mix the two ingredients together with a hoe.
Add eight shovels of sand to the marble and cement powder and mix the three ingredients together with a hoe. The sand will provide strength for the dried marble mix. Eliminate lumps from the mixture by chopping them with the hoe and blending them with the ingredients.
Fill a bucket with water and add three gallons of water to the dry mix, blending with the hoe. The mixture should resemble pancake batter. If the mixture is too dry, then add more water—one-half gallon at a time. If the mix is too wet, add more marble mix rather than cement. It is better to have more marble than cement.
Add cement fibers to the mixture. You can purchase these small fibers from any hardware store or cement manufacturer. These fibers will strengthen the marble mix once it dries. Combine the fibers completely into the wet mix with the hoe. After the marble cast has dried, these fibers will extend from the surface. Remove them by rubbing the marble with fine sandpaper.