Concrete is a strong and durable building material that, when properly mixed and placed, can last for decades with only minimal maintenance. One of the things that makes concrete so strong is the sand and gravel aggregate used in the mix. This rocky material naturally makes concrete heavy, limiting its transportation and use on some occasions. Making concrete lighter is possible, though, simply by replacing the aggregate with a lighter material such as pumice. The substitute mixture, known as Pumice-Crete, uses the porous crushed volcanic rock to create a lighter concrete that even acts as a moderate insulator. The Pumice-Crete can be used in applications where concrete is the norm, creating long lasting, load-bearing walls weighing a fraction of what traditional concrete weighs.
Pour 2 1/2 bags of Portland cement into a wheelbarrow.
Add 1 cubic yard of crushed, pea-sized pumice into the wheelbarrow. Mix the pumice and the cement thoroughly using a hoe to shift the material, folding it from the bottom of the mix to the top, until cement covers all the aggregate.
Fill a 5-gallon bucket with water, and add the water to the mixture. Mix the water into the pumice and cement, folding the dry ingredients over into the water to wet the mix. Add more water as needed until wet cement covers all the pea-sized pumice.
Use the Pumice-Crete atop normal concrete foundations for support in building one or two story structures. Pour the Pumice-Crete in concrete forms, allowing the mix to dry completely before using the structure.