[Stoves] Fly ash cement, Curiosity.

Crispin Pemberton-Pigott crispinpigott at outlook.com
Sat Feb 7 15:41:03 CST 2015


Yes exactly, Andrew.

Good memory.

If it was setting with water then that reaction‎ is undone with heating. I was wondering if there was a form if fly ash cement that was working like the fireclay cement which is a mix of regular cement and clays chosen to start melting at low temperatures.

Anything is possible.

The ash melting point is included in a standard coal analysis. Maybe someone got imaginative. With some fluxes included it would be a 'fireclay' based on fly ash. Ever heard of that?

The limiting temperature would be the melting point of the major ash constituent - some kind of silica.

I have used castable refractories but never one that claimed to be based on fly ash. Fly ash cement is common in Africa. It is about 5% cheaper that OPC, maybe. It is definitely slower curing in the first few days.
What's the elemental composition of wood ash? Where's Lodoysamba...?

Regards
Crispin
From: ajheggie at gmail.com
Sent: Sunday, February 8, 2015 02:33
To: Discussion of biomass cooking stoves
Reply To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Fly ash cement, Curiosity.


[Default] On Sat, 7 Feb 2015 13:28:09 -0500,Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:

>It is however still a hydrating mix (sets with addition of water which is absorbed and converts the lime back into limestone).

Careful Crispin I think you are mixing up two different processes,
hydrating will be the re attaching of water molecules to the oxidised
ash. Typically I think it is silicates of aluminium which re absorb
their waters of crystallisation and it is the growth of these crystals
that causes setting before the lime reaction.  Lime is first slaked
from CaO to Ca(OH)2 and this gradually re absorbs CO2 from the air to
form the calcium carbonate again.

Either will presumably fail when heated past your 400C temperature. I
thought it was you who recently pointed out a successful cement and
clay mixture works because the clay particles vitrify as the water and
carbon dioxide are driven off and hence hold the matrix together?

AJH

_______________________________________________
Stoves mailing list

to Send a Message to the list, use the email address
stoves at lists.bioenergylists.org

to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org

for more Biomass Cooking Stoves,  News and Information see our web site:
http://stoves.bioenergylists.org/


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20150208/5e28f9a5/attachment.html>


More information about the Stoves mailing list