How to Make Concrete Foam

Foam concrete sounds like an oxymoron, but it is used extensively in do-it-yourself home projects both big and small. Fire resistant and insulating, foam concrete is a versatile product that can be either decorative or beneficial to a building project. Mixing up a batch requires a minimum amount of tools and skill for the average DIYer, and the benefits are bountiful.

The cement-based slurry that creates foam concrete is made up of a foaming agent and typical mortar. Concrete foam was originally used as insulation in the 1920s. The material was brought into home construction projects in the '80s where it was used as an inexpensive patch alternative for walkways and walls. It was also found easy to manipulate and form molds that were inexpensive to make and light enough to move around. It has the benefits of being stress-free to construct and contains fewer chemicals, which crafters tend to prefer for small projects around the home.

Concrete foam works well for seasonal decorations, such as Halloween yard tombstones or large outdoor planters. It can be painted or otherwise decorated and is resistant to the outdoor elements. It can also be used for insulation around outdoor ponds, building retaining walls in the garden and the construction of eco-friendly, weather-resistant and resilient floor panels.

Foam concrete can also be used as a filler to remedy broken brick patios or filling in unused pipes too deep or expensive to dig up. There are many types and styles of formwork or molds for casting that can finish off your project in hours after the foam concrete has cured at least overnight.

Foam concrete mix itself is made of fine sand, cement, water and stabilizing foam. A standard recipe is 2 parts of cement and fine, dry sand to 1 part water and foam generator. You will want to have a quality foam generator to get the best results.

Commercial foaming agents or generators are often detergent-based, so you can get away with using an over-the-counter dish detergent, such as Dawn, Axion, Seventh Generation Natural Dish Liquid or any other name brand detergent. Dilute the detergent 1-to-40, or 2 cups of detergent to 5 gallons of water.

A concrete mixer pulls the ingredients together and gives you the aeration you need.

Mix the dry ingredients together thoroughly before adding the water in small amounts. Once the water is imbued into the mix, add the foam generator. Mix well before you weigh it to ensure you have a solid blend. A large kitchen scale can easily assess the weight of your foam, which should weigh in at approximately 3 ounces per quart.

Always use protective eye wear and suitable gloves when handling the ingredients to make foam concrete. Long pants and long sleeved shirts keep the sticky mortar from adhering to your skin.