Concrete is one of the most common materials used in construction today. It is actually a complex composite material made from Portland cement, aggregate, water and various chemical additives. The aggregate in concrete can be anything from crushed stone and rock, granite, limestone, river stones and similar types of rocks. If you want to achieve a smooth and even look of a concrete block, the method will differ depending on whether you are making a new mixture for a concrete block or repairing an existing one.
Add fine aggregate into the mixture when making concrete. Usually, the aggregate consists of crushed stone or small rocks, so when the concrete sets down in a cast and hardens, the result is often a rough and uneven surface. Add an aggregate as fine and smooth as sand.
Use a special type of a cast for your concrete blocks. There are many different casts on the market that offer different finishes and surfaces of concrete blocks. However, even if you use one of these special casts, you will still have to mix a finer aggregate into the concrete mixture.
Pour the concrete inside the casts, over steel or without any steel depending on the type of the structure, until the cast is filled.
Disassemble and remove the cast two days after pouring the cement, while the concrete is not yet fully cured. Then leave the cement block to set, dry and harden over a period of 28 days.
Make a concrete mixture using a fine aggregate such as sand. Make sure to mix all the ingredients thoroughly so you get a smooth, homogenous concrete paste. You can also use a small bag of ready-mix concrete for this project.
Apply the smooth concrete mixture onto the thoroughly wet surface of the concrete block. Use a trowel to apply and then even out the new layer of concrete. There are a few shapes of trowels you can use so chose the one most suitable for your concrete block.
Leave the new layer of concrete to dry and adhere to the existing concrete block for at least 24 hours. During that time, the water you used to soak the block will help the adhering process.
Resurface your concrete block using a grinder tool. This is a good and practical solution if you don’t want to add additional concrete mass to your block, meaning if you don’t want to make is any bigger. Choose a versatile hand grinder to even out the surface of the concrete block and make it smoother.
For a more seamless look, finish the concrete block with a layer of clear sealer after the grinding process.
Wear sturdy working gloves when mixing concrete and making concrete blocks.