How to Make Lightweight Concrete

Concrete is a versatile building material that is used to create floors, walls, countertops and sidewalks. Although the weight of concrete is not usually a consideration when using it for floors or sidewalks, concrete weight is important when used in other projects such as walls or countertops. The weight of concrete is determined mainly by the type of rock that is mixed into the concrete powder. Changing the type of rock changes the weight of the concrete as well.

Things You'll Need

• Concrete mixer
• Water
• Cement, 94 lb.
• Sand
• 5-gallon bucket
• 25 gallons lightweight aggregate
• Shovel
• Wheelbarrow

Instructions

1. Select a lightweight aggregate to mix into the concrete. Some lightweight aggregate options are: perlite, vermiculite, volcanic rock and expanded shale. Choose a type that is local to your area to reduce the construction cost.

2. Pour 5 gallons of water into a concrete mixer which can be rented at home improvement or equipment supply stores.

3. Add 1/2 of the cement into the concrete mixer and mix thoroughly. Then, pour all of the sand into the mixer and allow to mix for several seconds. Add the remainder of the cement and mix well for one minute. The mixture should be soupy in texture. Add additional water if the mixture is too thick.

4. Pour the selected aggregate into a 5-gallon bucket and then pour it into the concrete mixer. Mix well and then add 4 additional buckets of aggregate, mixing well after each addition.

5. Apply the lightweight concrete mixture as desired.

Tips & Warnings

• Lightweight concrete is best suited for indoor use, although some use it for outdoor purposes as well.

• Always wear a mask and eye protection when handling cement or the perlite.

• Lightweight concrete is mainly used in decorative surfaces, as it is much weaker than traditional concrete.

• Do not use lightweight concrete for steps, pavers or floors because it is not strong enough to support foot traffic.

• To mix the concrete by hand, reduce the percentages by half and use a wheelbarrow and shovel.

References

• The Mold Store: Lightweight and Medium-Weight Concrete Mix Designs