How to Make Lightweight Concrete Blocks

From privacy screens to walkways to outdoor fireplaces, concrete blocks have many uses around the home. However, traditional concrete blocks are often awkward to handle and can be unsuitable for certain projects due to their weight. Fortunately, lightweight concrete blocks are a great alternative that is not only easier to work with, but they are also easy to make. By following these simple instructions, you can create your own lightweight concrete blocks for whatever DIY project you have in mind.

Prep the Materials

Lightweight concrete blocks are made by adjusting the ratio of the concrete mix with a lightweight aggregate, like Perlite. With that in mind, the amount of aggregate substitution depends on the type of project. If you are using the concrete indoors or in a place unaffected by weather, then a full lightweight mix is acceptable. However, for most outdoor projects, you want to make sure you use more of a medium mix that will be able to withstand the elements. Remember, the lighter the concrete, the weaker the block.

Mix Water

To begin the process, add five gallons of water to the mixer. If you are planning on changing the color of the blocks, then insert dyes, colorants or other tinting additives at this time. Once everything is thoroughly mixed, proceed to the next step. If using a mixer is not an option, you can create concrete blocks by hand. However, if you plan on using your hands for the mixing, then cut this formula in half to make it easier to mix.

Add Cement Mix

With the water and additives mixed thoroughly, pour in the cement. For this particular mixture, it is recommended to use a 94-pound bag of cement. You should add no more than half of the bag at a time, allowing the mix to reach a good consistency before adding in the other half. Once the entire bag has been incorporated into the mixture, start preparing the Perlite.

Add Sand

The sand is the part of the mix that makes the concrete heavier. If you want the ultimate lightweight mixture, then only use one five-gallon bucket of sand. For more of a medium grade concrete, which is stronger, add in an extra bucket of sand. Keep in mind that the lighter the concrete the weaker the hold, so make sure the formula you use is appropriate for the project at hand. As you did in the previous steps, wait for the sand to mix in well before proceeding to the next step.

Add Perlite

The Perlite acts as a lightweight aggregate. Fill five buckets with Perlite for a total of 25 gallons. Only pour one bucket at a time into the mix and wait for the Perlite to mix in completely before pouring in another bucket. You will notice that the concrete will start to thicken as you continue adding in the Perlite. This is normal as the Perlite actually absorbs the water. Stop adding Perlite once the mixture has reached a thick enough consistency to pour into the molds.

Molds

Once the mixture has reached the right consistency it is ready to pour into your molds. Although this process is fairly straightforward, there are some tips that will ensure the concrete properly cures. For starters, make sure you are working on a level surface. Begin by pouring the concrete into the molds. After this is completed, cover the molds with a layer of plastic. The plastic will help strengthen the concrete and ensure the curing process goes smoothly as planned.

Drying

After the molds are covered, you will need to wait approximately 24 hours before uncovering and removing the molds. With the concrete out of the mold, cover it back up with plastic and place in a location that is out of direct sunlight and constant wind. It typically takes a long time for the concrete to properly cure, so you will need to refer to the concrete mixture to see how long. Normally, the wait time is around a month, though it varies depending on the mixture.

Installation

After the concrete has fully cured then it is ready for installation. Although the process for making concrete blocks is rather lengthy, the end result will last you from anywhere from 50 to 100 years.