posted 2 years ago
He is directly talking about Hemp and natural fibers in concrete / lime here.. I'm trying to understand it.
Convo On YT
Aaron Franklin
Bollocks. You cannot use Portland cement or any Calcium Oxide or hydroxide based systems with sawdust or natural fibres or glass fibres if you want ANY strength or water resistance
You need a Magnesium oxide system. The high alkalinity depolymerises cellulose and lignins and eats glass.
MgO activated with MgCl2 or MgSO4 is compatible with timber and natural or glass fibres.
Activated with fumed silica is more water resistant. Activated with potassium, sodium or ammonium Phosphate is strongest and most seawater resistant.
You can use dolomite lime as a filler but not if it's calcined to CaO and MgO.
That stuff will not last or have any strength. Like hempcrete made with Ca0 it's only suitable for drywall insulation.
Seawater is 6% Magnesium dry salt weight.
Roman concrete is doleritic Volcanic ash calcined at low temp to fumed silica, and high Magnesium oxide and iron oxides relative to calcium content. And activated with seawater for the extra Magnesium and sodium and chloride to activate and provide charge balancing captions. And bone ash as phosphate source.
the caustic alkalinity of Portland cement due to CaOH cleaves ester bonds in the natural fibres and attacks glass.
Also the moisture content changes cause swelling and shrinkage in both Portland concretes and especially sawdust.
Just with temperature and humidity changes.
MgO systems are less porous, have far greater elasticity, not brittle. Don't swell and shrink much at all.
So in addition to adhering, are better in every way.
Including not turning all the oils in your skin into soap and dissolving your skin like Portland or CaOH slaked lime.
yeah Magnesium oxide you can buy from rural fertiliser shop.
You can get Magnesium chloride there too.
And Epsom salts which is Magnesium sulphate.
Either the sulphate or chloride work similarly well at 10-50% by weight.
You'll have to test the range of mix ratios to give best results. There is very high water of crystalisation in some of these.
And your fillers like sawdust, clay, sand etc can be reactive and change ratios a little.
Yes you can use any standard Portland cement type rebar etc. But any fibreglass or whatever for Portland will be embedded in waterproof snot or plastic coated to stop the cement dissolving it.
Plasticiser, probably. But you probably won't need it.
Portland formulations usually use some plaster of Paris to make them appear to have set in the first few hours.
And then gradually ACTUALLY set over weeks to years.
So your losing pourability, aggregate fill ratio.... and workability by immediate sticking together of bits of aggregate with Calcium sulphate- plaster of Paris blobs, and skins, with not ultimate strength or water resistance.
particularly if they are dry bits and sucking in the water.
This is helpful with MgO cements like Chloride or Sulphate activated Sorel.
There's Sorell and Sorel. Different chemists different centuries, one used Zinc, the other Magnesium.
For the rapid set Super strong, ultrachemical resistant chemically bonded Phosphate ceramics of Magnesium, Aluminium, Silica, Iron etc.
Those are supermaterials that can handle highly corrosive high, strength, cryogenic to up to 2800 degree temps.
Are also cheaper than woodchips.
Like mixing some phosphoric acid or phosphate fertiliser with your Magnesium, or calcium or Silicon or zinc or titanium or Aluminium or iron oxides.
To produce anything from a one coat ceramic impervious and indestructible coating on rusty or clean steelwork for military Naval applications. To rocket exhausts, jet turbines or Formula 1 disk brakes.
Gets stronger with aging, including repeat ground or seawater or chemical soaking and roasting dry....
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