Curing Concrete With Vermiculite

level on a partially finished concrete floor
What You'll Need
Large container
Plastic sheeting

Vermiculite mixed with concrete creates a lightweight concrete that will cure in a longer amount of time. A longer curing time equals stronger concrete. Here’s what you need to know about using vermiculite.

1. What Is Vermiculite?

Vermiculite is a type of aggregate that is created when volcanic rock is heated to extreme temperatures. The heating process causes the rock to expand. When this is combined with concrete it expands the concrete and creates a lighter structure. This is especially useful in lawn ornaments, walkways, and even walls.

2. How to Measure the Ratio

mixing concrete in a bucket

When you are working with vermiculite you need to know how to measure out the ratio of vermiculite and concrete. A lot of the ratio will depend on the specific project you are working on. In general, a good ratio for most projects will be three parts vermiculite to one part concrete. Above ground pools may use a ratio of seven to one. You want to check to ensure you are using the correct ratio for your project. Remember the concrete is really only used as a binding agent for the vermiculite.

3. Measuring Your Water

The first thing you want to do when using vermiculite is to measure out the water you need and add it to a large container to mix. You will then add the concrete and mix it well. The last step will be to add your vermiculite to the mix. Add in a little at a time and add more water if you need to. You want the consistency to be like mud.

4. Allow Time to Cure

Once your mixture is ready you will want to pour it into the mold. Make sure you are using plastic sheeting to cover the area once you’ve poured it. You also want to make sure you allow plenty of time to cure the concrete. Remember when using vermiculite that the curing time will take longer.

5. How to Tell It’s Set Completely

concrete sidewalk

When we say that it takes a long time to cure, we mean it! In most cases you are looking at several days if not longer.

During the cure time you may see a point where the concrete looks almost flaky. It may look like it’s easily crushable, and many people start to worry that something went wrong. This is actually normal. Artists like using this material because at this point it’s easy to sculpt. Just allow it to set for a few more days and it should harden up and not look like this.

6. Pre-Soaking

Some people find it easier to work with vermiculite if it’s been soaked overnight first. This will depend on what you are creating. Soaking it will help to prevent cracks from forming and will keep the vermiculite damp while you work with it. This will work best on objects that you want a faster cure time, but still want the benefits of using vermiculite. It makes it easier to mix as well.

Others will tell you that presoaking it will give you more problems. So when you are first using this, play around and see what works best for you.

7. Health Concerns

Vermiculite was made with asbestos until the early 1990’s. This has caused a lot of controversy over whether or not the product is safe to use. Companies who mine the product are now required to have the mines and the materials tested regularly for asbestos contamination. Check with product companies to ensure your product is safe.