Lightweight Concrete Mixes

Lightweight concrete can range from only slightly lighter than a traditional concrete all the way up to engineered mixes that are as much as 90% lighter than regular concrete. In general the concept with lightweight concrete is that the lighter that you go, the weaker the concrete will be. For this reason each lightweight concrete mix will be suitable for only a few select types of projects and would be unsuitable for much else. In addition to compromising the finished strength of the concrete, most lightweight concrete mixes require special finishing techniques and considerations.

Vermiculite

Vermiculite is a mineral that has tremendous insulating properties and is the most commonly used lightweight concrete additive. House insulation was made from ground up vermiculite for a period of time however this contained asbestos. Vermiculite purchased today does not have asbestos in it and it can be used safely though a mask is recommended when working with this or any concrete product. Vermiculite looks like perlite except instead of white, vermiculite is a brown and tan color with a distinct gold shimmer to it. You can purchase vermiculite under the name pool base, which is a modified shredded vermiculite product often used to coat the floor of vinyl liner swimming pools.

Perlite

Perlite is technically a volcanic glass but has many purposes only one of which is being a lightweight concrete additive. Similar in size to vermiculite, perlite is white and can be found in almost any gardening store. Perlite does not absorb water as readily as vermiculite making it much harder to place and finish, and is not as strong as a vermiculite concrete mix.

Sawdust

Sawdust can be added to concrete as a lightweight alternative to sand with some degree of success. Concrete made with anything more than a minimal amount of sawdust stands the distinct chance of failing in the finished product. Heavy use of sawdust in a concrete mix would almost certainly compromise the integrity of the mix beyond any useful degree. Additionally adding organic material to concrete can have adverse reactions. Organic material will biodegrade leaving the concrete weakened and exposed to damage.

Peat Moss

Peat moss can be used as a lightweight concrete additive. Mixes made with peat moss as an aggregate is often referred to as hypertuffa. This mix is weak overall and mostly unsuitable for construction purposes. Most commonly peat moss infused concrete is used to make sculptures, art and craft items. Detail from hypertuffa is difficult due to the coarse nature of the peat moss.

Proceed to the section on Mix Proportions