Lightweight Concrete
Lightweight Concrete Mixes
Using lightweight concrete aggregates will dramatically decrease the strength of the finished concrete. Experimentation is strongly recommended with lightweight mixtures to ensure that the concrete will be suitable for your purposes.
There are a few reasons why making lightweight concrete will require practice in order to get the mix ratio just right. When mixing cement it is always very important to observe mixing ratios however lightweight concrete is even easier to have a problem with.
In a traditional concrete mix you can make a small mistake on your ratio and you would likely never know it as the concrete will still be very strong. With a lightweight mix it is very easy to end up with a crumbling mix that is not even strong enough to support its own weight.
Starting with the basic high strength mortar mix you will replace the sand by volume with any one of the following aggregate replacements:
- vermiculite
- perlite
- peat moss
- wood shavings / sawdust
- pumice
- foam
Each of these aggregate replacements will change the look, strength and workability of the cement. The larger the size of the lightweight aggregate and the more lightweight material that you substitute in place of sand, the greater the strength will be reduced. A lightweight concrete mix with 1.5 parts sand and 1.5 parts lightweight material would still be strong enough for many applications. Ratios where even less sand is used will start to create near to unusable results in the concrete strength.
Read more about aggregates in the concrete aggregates section