Primitive Technology: Wood Ash Cement

Primitive Technology: Wood Ash Cement – Creating wood ash cement from scratch
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Partial credit for this idea goes to James Keane who I discussed this with on my wordpress site (see conversation):
I developed an experimental cement from made only from re-fired wood ash as its cementitious material. It was mixed with crushed terracotta as an aggregate and formed into a cube. The cement set hard after 3 days and did not dissolve in water after this period.
Process: First I burnt bark and leaves in a kiln at high temperatures to produce well burnt, mostly white wood ash. The ash was then mixed into water and stirred well. The excess water was poured off and the resulting paste was made into pellets and allowed to dry. A pellet was then re-heated in the forge until it glowed about orange hot. This was then taken out, cooled and dropped in a pot of water. The pellet dissolved and boiled due to a chemical reaction with the water. The paste was stirred and crushed terracotta (old tiles from previous projects) was added and mixed to form a mouldable mortar. This was formed into a cube and allowed to set for three days (in the video, a cube made exactly the same way 3 days previously was used due to time constraints). The resultant cube was strong and made a slight ringing sound when tapped with a finger nail. It was placed in water for 24 hours to simulate a very heavy rain event and did not dissolve or release residues into the water.
My current theory: The main component of wood ash consists of calcium in some form (e.g. calcium carbonate, calcium oxide). This can be up to 45% from my research. Calcium is in higher concentration in the bark and leaves of a tree. When the ash is mixed with water, the soluble component of wood ash (10% pot ash) dissolves into the water. But seeing that it does nothing for the cementing process, it is drained off leaving the insoluble calcium (and other components) in the paste. Doing this probably raises the relative percentage of calcium in the paste to about 50% or more. Most of the other 50 % consists of silica and alumina which are pozzolans, materials that chemically react with calcium hydroxide to increase the durability of the cement product. The paste was then made into a pellet and fired again to high temperature to convert all the calcium compounds to calcium oxide. It also reduces any charcoal in the pellet to ash if it hadn’t already been burnt the first time. This step seemed important as un-fired ash pellets only partially hardened and would fall apart in water, though retaining a weak undissolved 5mm thick crust. I can only surmise that re-firing the ash just gave a greater conversion of the calcium components to calcium oxide. The pellet is slaked in water converting the calcium oxide to calcium hydroxide. This cement was mixed with crushed terracotta which may also help in some way that I’m not aware of as I only did this one experiment and did not test other aggregates yet (e.g. sand, gravel etc.). Terracotta is porous and might hold together better than other materials. The mixture is allowed to set in air where carbon dioxide reacts with calcium hydroxide to form calcium carbonate cementing the aggregate together. After this, the cement will not dissolve in water.
Use: I think this material might have a potential use as a mortar holding rocks or bricks together in wet environments where limestone or snail shells are unavailable for making cement. Wood ash is a pretty ubiquitous material to most natural environments inhabited by people using biomass fuels. Wood ash cement turns a waste product into a valuable building material. From my research, wood ash is already being used as a partial replacement for cement in the building industry without decreases in strength of the final product. But I’ve only just started experimenting with it and don’t know its full capabilities and limitations. Calcium content of wood ash differs depending on the species of tree, the part of the tree burnt and the soil it’s grown on. Cautious experimentation is still required before committing to a hut built from this material.



47 responses to “Primitive Technology: Wood Ash Cement”

  1. Primitive Technology Avatar

    I think I have the chemistry right. If any chemists are watching correct me if I'm wrong. The calcium compounds are converted to calcium oxide in the second firing, turn to calcium hydroxide in the water and then set to calcium carbonate in the air. There maybe a pozzolanic effect due to the alumina and silica in the ash too. The end product is a cube made only from wood ash (fired twice) and crushed pottery. It sets hard after 3 days and will not dissolve in water even when fully submerged for 24 hours. Thanks.

  2. Oscar Shibata Avatar

    What A High Skill Survival You Have It, Man!

  3. meraukePapua Dion Avatar

    Whats the name stone reds..primiteve thecknologi…..please

  4. Richard Wong Avatar

    Not exactly relevant to making concrete, but how did you cut that circular stone at 2:37? You should make a millstone to help with crushing/grinding all your materials

  5. Wholy ❶ Avatar

    Great, I will use this on my crafting table xD

  6. dominic rivera Avatar

    How dp you scavenge for clay?

  7. Jackle_Raid Avatar

    It would be nice if he would have words appear and say what the rock he used probably is

  8. mary sunshine Avatar

    That's It. I'm going to build a house.

  9. Hiro Ciko Avatar

    Okay this already make cement, soon enough he will make copper iron steel then vibranium…

  10. Ainsley Hinson Avatar

    The OG asmr channel

  11. Aegius_X3 Avatar

    How long until the mortar and pestle

  12. Gerway Rekka McGillen Avatar

    If you're trying to get a higher concentration of ash in the water a good method would be to mix it in while heating the water over a fire. This should allow for more ash to mix in, and will leave the solution supersaturated once it cools. I could be wrong, this is just based off of the stuff I was taught in chemistry class a couple years ago.

  13. Ron D Avatar

    This the OG wilderness survival guy ❤️

  14. NoFate2010 Avatar

    А теперь представьте, что его найдут австралийские аборигены?!
    Да он у них королем станет.

  15. Godwin John Dela Cruz Avatar

    Try to reduce the water as much as you can because it will make your concrete as hard as possible. Also, soak it in water in few days for curing.

  16. Gatling Della Avatar

    I know what I’m doing in the holidays

  17. Spider Boy Avatar

    Before you start building some tower, I just want to tell you that the height limit is only 256 blocks.

  18. Decymus Peraza Avatar

    wait thats not wood.

  19. Rupert Schorn Avatar

    5 years from now he will be manufacturing a nuclear reactor

  20. رسلان لونا Avatar

    اإن مكرر نننة أو نلنلتقبعد د طو كويس مكنتش كسض

  21. ItsJohn K Avatar

    Is this channel sponsored by Donald Trump?
    Cause your forest is like a private place for you

  22. Kyle Dudley Avatar

    Watch with subtitles on. You are welcome

  23. Adam Lujan Avatar

    Id love to survive with this guy

  24. fight4anarchy Avatar

    Forgive my ignorance and possibly stupid question. But whats the brown stuff you mixed it with? Just dirt? Some sort of stone? TIA lads.

  25. Сергей Петров Avatar

    Ash only ? Can other trees be used ?

  26. hoper man Avatar

    Can we build a pool with it?

  27. Ẩm Thực Anh Em Avatar

    vietnam hello guys .. you guys come to my channel to support me, thank you

  28. SlyDz420 Avatar

    Awesome as always.

  29. SuperMarioDylan Avatar

    This channel will become medieval,-how to build a castle- How to make iron knight armor How to abort How to make diamond armor How to be the king of a castle

  30. Exempty Avatar

    A… S… M… R… Survival

  31. Alex Lee Avatar

    The Asia already knew this and that's why you pick it up and are trying to take away it away as your discovery the cool mines no this already too .stop stealing WHAT other people invented.

  32. Felix Larios Avatar

    Nature is trying to do a ASMR

  33. mario amor Avatar

    Hay alguna formula ignífuga con tierra normal?

  34. DACRACKING Avatar

    That does not make alot from all that ash

  35. Richard Salvino Avatar

    If you watch these videos without captions you probably got bad teeth and body odor

  36. Atom Avatar

    우와! 신기방기.
    근데 한국인은 없나?

  37. Critique aquatique Avatar

    Une fois qu'on a fait la boulette de cendre, il faut la faire cuire sur le feu ?

  38. thiago 17777 mito Avatar

    melhor canal mano ensina muita coisa

  39. The Color Yellow Avatar

    The OG. I always come back.

  40. Lauri Laukkanen Avatar

    @2:20 you must have fingers of steel…

  41. TheOneAndOnly Avatar

    I made one today and hopefully it doesn’t crack

  42. Siva Teja Avatar

    Sir I respect your hard work

  43. Lucifer Morning Star Avatar

    What is the orange red thing

  44. grey Day Avatar

    Take u a year to make the front step

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