Lightweight Wood Concrete Pot

Wood concrete is not a new invention. The material has been used many times since the 1930s, even for building houses.

Ordinary concrete requires cement as an adhesive and stones of all sizes as fillers (additives). It is important to ensure a balanced mix so that potential spaces between large stones are filled with small and very small grains of sand. Only in this way can the desired strength and durability be ensured.

Cement alone will not hold. After all, you don't just use superglue when you're doing handicrafts; you also put paper, wood, plastic and other materials together.

Sand in various grain sizes is now a rare resource on this planet. Wood is a renewable and lightweight raw material.

Cement

Wood shavings

Water

Some buckets

Trowel, small shovel, wooden lath

Optional: silicate or chalk paints

I use small wood shavings, not sawdust, as an aggregate for our pot. I have also used longer shavings before, but they were quite difficult to mix.

For the wood concrete I use 5 parts by weight cement and 1 part by weight wood.

Cement has a specific density of about 1.1 kg/litre and wood chips 0.4 kg/litre. Cement is therefore 2.75 times heavier than wood. This results in a ratio of 1.0 litre of cement : 0.55 litre of wood.

I use a tin can with a volume of 0.45 litres for measuring. It does not have to be exact to the gram.

Okay, to make a long story short: 2 cups of cement to one cup of wood chips. Happy?

First you have to water the sawdust. If they were used dry, they would immediately take away the water necessary for the cement to set.

Put 5 cans of wood shavings in a bucket, add a lot of water, stir and leave to soak until the next day.

The next day: pour away the remaining water and squeeze out the sawdust. You can also use a strainer.

Since I already portioned the wood yesterday, I can use it all today. To the wet sawdust I add 10 cans of cement and mix long and carefully with a trowel. If the cement is too dry, carefully add water.

Then I fill the wood concrete about halfway into the larger mold. Afterwards I press the smaller form slowly into it and weigh it down with stones , so that it does not rise again from the mass.

The concrete must now be compacted. To do this, tamp and move the concrete with a wooden bar or a narrow trowel so that air bubbles escape and all the wood and concrete particles fit tightly together.

Check again to make sure the inner mold is centered.

Then let the mold set for two days.

After about two days, the pot can be released from the molds. The concrete is still quite wet, it must first dry for a few days.

The concrete will be more durable if the surface is sealed with paint.

But please use only natural paints like silicate colors or chalk colors! Then our pot can decompose into dust after a hopefully long lifetime and does not pollute the environment.

Weight: random 1000g, in this case results in a density of 1.3 g/ cm³.

Conventional concrete has a density of 1.8-2.4 g/cm³.

Advantage:

No sand is used, instead the local raw material wood. Compostable.

Even better: when the pot goes to landfill one day and disappears into the earth, carbon is also stored at the same time.

Disadvantage:

Production of cement consumes a lot of energy.

Use:

e.g. birdhouses, flower pots, sculptures, ...

Brainstorming: Other fibres could also serve as aggregates:

Paper/cardboard, textiles, dried leaves, dry hay or reed, hair, Bamboo strips, ...