[Stoves] Fly ash cement, Curiosity. Continued 2

[mtrevor at mail.mh]

Crispin and AJH 
Thank for the answers and I will keep looking.  Fly ash is high in aluminsilicate component  an important 
part of refractory cements and has a very strong base component. Part of the setting may not be all hydrolysis

Statements like “fly-ash-based geopolymers exhibit remarkable fire resistance while maintaining a high degree of mechanical strength.”
and
“The team has made geopolymers, a cement-like material formed by dissolving materials that contain silicon and aluminum, such as fly ash, in a highly alkaline solution for use in high-temperature applications such as fireproofing and building insulation. Rickard said: “Because of their amorphous polymeric structure, geopolymers maintain structural stability to much higher temperatures than conventional concrete.”


There maybe something here---  the Zeopbond group in Australia makes an E-crete--

Michael N Trevor
Instructor
College of the Marshall Islands



From: Crispin Pemberton-Pigott 
Sent: Sunday, February 08, 2015 6:28 AM
To: 'Discussion of biomass cooking stoves' 
Subject: Re: [Stoves] Fly ash cement, Curiosity.

Dear Michael

 

How’s things on the island?

 

>there is a growing body of information on fly ash cement.

 

It has become more popular as a way of cutting the price and using an otherwise waste pile next to power stations.

 

Fly ash (coal ash) is ground to micron size and mixed with Ordinary Portland Cement which is itself a mixture of dehydrated lime and clay.

 

It is usually sold with the fly ash content on the package such as “30%” (by weight). 

 

It cures more slowly than OPC and can be stronger.  It is however still a hydrating mix (sets with addition of water which is absorbed and converts the lime back into limestone).

 

>With a fire resistance up to 1200 degrees has any one done 

any serious work with it for rocket stoves? 

 

Well there I have to pause to think. Are you referring to fire clay cement? Fireclay cement can reach that temperature but there are a couple of types.

 

The point I thought I would make is that the hydrating portion of high temperature cements burns out above 400C.  That is why I was wondering about the mix.

 

Maybe you have read about a cement made entirely (almost?) of fly ash because that would be something that could ‘stick’ as it melts at high temp.  The ash melting temperature (which is not a single point – there are lots of things in there) could be maybe 1000-1300 which is in the range you mentioned.

 

>Sounds like a mix of fly ash cement with perlite might make a very 

good 5 gallon gallon rocket stove.

 

As long as both the filler and cement can take the temperature. Walls can get to 800 C on the surface pretty easily. 

 

>I did see one reference to an elbow for a rocket stove. If that is effective 

the boxes beach sand wood ash bucket etc could end up making rocket stove truly

easy to make.

 

If the beach sand is lime-based (coral) it will also burn out above 400.  Your solution seems to be to import (or dig up from the ocean floor?) some clay.

 

What is in fish bone ash? Is it silica?

 

Regards

Crispin far away



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