Refractory concrete with pumice

[Esteban Campestre Abejil]

This thread is related to the entitled First 4-inch batch box in Chili?

Chile (where I live) is a highly volcanic country. In 2011 a set of erupted volcanoes near the area where I live. As a result of these eruptions, many surrounding areas were covered with volcanic material. One such material is pumice.
The pumice resist high temperatures, has a high content of silica and alumina, has a low density (490-550 kg / m 3) and a thermal conductivity of 0.12 W / mK. It is, therefore, a good high temperature insulation.
Also, being very porous, it is quite absorbent.
It is a natural material that has no associated ecological footprint (except of course caused by the volcanic eruption that created it) and is available for free and near my home.

I got the idea of ​​build the "heat riser" and "batchbox" of my stove from refractory concrete using pumice as aggregate.

Some doubts:

How could compensate the high absorptive capacity of pumice, in order to not excessively dry cement mix?

What percentage of pumice should add to the mix?

Should I apply additional insulation?

Get refractory cement specially formulated for boilers or furnaces is difficult here. But is available at an affordable price (in bags of 10 kg) a refractory cement used as mortar for bonding refractory bricks.

I will do a test with this cement and various proportions of pumice, some bricks 10 cm thick. And I'll put it iside a stove for a couple of days to see how it goes.
I also want to empirically measure the insulating capacity of this concrete heating on one side with a blowtorch and taking note how hot achieved through it. Would it be a good way to get an idea of ​​its insulating capacity?


I remain attentive to your suggestions.


Esteban.

[satamax]

On thing often used in refractory concretes, is pozzolan.

[Esteban Campestre Abejil]

Although different, sometimes pumice is known as pozzolan, for their similar properties. Both materials are found in large quantities in Chile, but pozzolan is more focused on the central area. Instead pumice is found in almost all regions of Chile. In addition, the pumice is usually found on the surface, commonly floating in lakes, rivers and even the sea.

[Dan (Upstate NY, USA)]

How could compensate the high absorptive capacity of pumice, in order to not excessively dry cement mix?

What percentage of pumice should add to the mix?

Should I apply additional insulation?

I am afraid no one here has the answers to these questions, but you'll find out when you try and make sure to share the results with us when you do.

[Deleted]

Aug 21, 2014 11:25:20 GMT -8 Esteban Campestre Abejil said:

Although different, sometimes pumice is known as pozzolan, for their similar properties.

Pumice is the original pozzolan named from its origin by Pozzuoli
a city of the province of Naples, in the Italian region of Campania.

Pulverize pumice and mix it with lime and you can make Roman concrete.
Alternatively one can use hydroxides of sodium or potassium to activate
the pulverized pumice and get a geopolymer.

[Esteban Campestre Abejil]

o.O

Are you very sure about ir?!?! Karl! This is a wonderfull new for me!!! Years ago I read that pozzolan is the base for Roman concrete, but nobody can tell me the how.

I'll try it!!! I will!!!

Any idea about how can I tranform this Pumice Roman Concrete or this geopolymer into a refractary one?

[Deleted]

The composition of pumice and thus the prop3rties varies by location.
Melting point: usualy etween 1350°C and 1700°C, but can be lower if lots of flux is contained.
Al2O3 13-17%

With lime it will form calcium silicate hydrates and calcium aluminosilicate hydrates.
The hydrates will be driven off at firing.
Calcium silicates/aluminosilicates have melting points above 1400°C.

Geopolymerisation will raise melting points too.

For Roman concrete add about 30% lime.

For geopolymers one can use lye alone or combined with lime.

For refractories do not use sand as aggregate as different thermal expansion
will weaken the structure and may even destroy it over time.

[Esteban Campestre Abejil]

I understand.

In short, enough milled pumice stone (like dust) mixed with sodium hydroxide (and what else?) Would fire resistant geopolymer.
The problem would be in the aggregate. I can not use sand, but perhaps pumice fine-grained (1-4 mm, will be fine?).

If this is correct, my problem would be how to transform powdered pumice at home.

Thanx Karl!

[Esteban Campestre Abejil]

How much should I grind pumice (not for use as aggregate, but as cement)?

[Deleted]

Usualy a mixture of lye and waterglass is used,
but from my experiments the waterglass is not absolutely required.
I have linked a lot of papers in the forum.

Pumice fine-grained could be used as aggregate.

For powdering a large hammer and eye protection should do it.

[Esteban Campestre Abejil]

Great!!!

[Deleted]

Aug 22, 2014 7:12:25 GMT -8 Esteban Campestre Abejil said:

How much should I grind pumice (not for use as aggregate, but as cement)?

The relation of binder to aggregate is the same as by normal concrete.

[Esteban Campestre Abejil]

Aug 22, 2014 7:33:28 GMT -8 @karl said:

I have linked a lot of papers in the forum.

A lot of information. I'll be reading for years ... English !!! o.O

Thank you!