This science activity video on making wood ash cement from scratch by using refired wood and terracotta is an experimental video presented by the Aussie survival instructor at Primitive Technology.
More than 2 billion tons of cement are produced each year. Cement is the most widely used raw material to build homes and some of the tallest buildings that you see around yourself.
Cement that we know today was invented by England in the 19th century. It was made by heating various raw materials such as limestone, silica, clay, shells, and much more.
However, what would you say if I told you the secret of how to make cement in the wilderness? Seems absurd, but this is true! You will need no tools to make wood ash cement which you can make out of scratch in the wild.
Steps of making wood ash cement from scratch
Courtesy: Primitive Technology
(Note: Adult supervision is necessary)
- First, collect a huge pile of fallen bark and leaves of the Eucalyptus or any other tree.
- Now, burn the collected bark and leaves in an outdoor clay kiln at a high temperature.
- Next, mix the produced white wood ash that has no charcoal in it with fresh water and stir well.
- Pour off the excess water so that it seems to be a thick paste.
- Compress the paste with your hands and make a small rounded mass out of the paste
- Allow these pellets to dry for some time and then reheat them in the fire till they become hot and orange.
- Now take them out of the fire, allow them to cool, and then drop them into a pot of water
- Stir the mixture well, and the pellet will get dissolved in the water
- Now take some terracotta tiles and crush them with a stone.
- Add the crushed terracotta tiles into the pot with dissolved pellets till it becomes a mouldable mixture.
- Next, upturn the pot on a large stone. Form a cube with the mouldable mixture by the pressure of your hands
- Now, let the cube set for three to four days, and the resultant cube will become hard.
- Finally, place the cube in a pot of water and it will not dissolve into the water.
- Yes, you now have the wood ash cement that you can use!
By Pursuing this experiment, we will get wood ash cement that is suitable for building homes.
See, the fallen bark and leaves contain a high concentration of calcium (approximately 25-50% calcium compounds).
So, when the fine ash with no charcoal is dissolved into water, the soluble component of wood ash also gets dissolved, and calcium hydroxide is formed.
However, when you drain the excess water, a residue of insoluble calcium hydroxide and calcium carbonate is left, which eventually increases the calcium concentration in the remaining paste.
Now, when this paste is compressed, which will be turned into pellets that are dried, and then heated. Wood ash paste is still not hard enough like cement.
This becomes evident when the pellets are cooled and dropped into water. Well, this is because it is still not mixed with crushed terracotta tiles that will give its strength.
When crushed terracotta tiles are added to the paste, the porous property of terracotta( a type of fired clay) acts as a binder. So, when the cube formed out of this wood ash and crushed terracotta is left for 3-4 days.
So it becomes hard like cement. Surprising to know that terracotta is still used as a popular roofing material in many parts of the world.
Can wood ash be used as cement?
Yes, wood ash (WA) can definitely be used as cement. It is already used by the construction industry as a partial replacement for cement because it is an energy-extensive commodity and releases a massive amount of CO2.
Hence, they are using wood ash, which does not contribute to environmental degradation and is also strong enough to replace cement in a blended format.
Again, researchers have already found that wood ash has a significantly higher amount of aluminium, manganese, sodium, potassium, and magnesium than in comparison to cement.
This amazing video of making cement from wood ash gives a deep insight into natural elements that can be used to make cement.
However, it is essential to remember that the calcium content of wood ash might differ from one tree to another.
It depends on various factors such as tree species, part of the tree chosen for burning, the soil in which the tree has grown, combustion temperature, and so on.
So don’t disappoint when the wood ash cement does not seems to be strong from the first trial.