expanded clay

[david s]

I've been experimenting a little with expanded clay as an insulating aggregate. The stuff is much denser than perlite or vermiculite, but is also way stronger. I have been using it where I want an insulator, but also need strength in that area. It has replaced a 50/50 mix of heavy aggregate and perlite. Because of the way the stuff is manufactured it is really strong. each grain is around 10 mm in diameter and are spherical in form. The outside is quite hard but the inside is full of holes and much softer.This is ideal because it gives them more strength while remaining pretty light. They cost me around double that of perlite, but I think I'll continue to use them. Anyone else had experience with using them or know of any building applications? They are generally used as a water filtration or water storage as a growing medium.

[Tscarborough]

Re: expanded clay

Expanded shale is used in CMU over here as well as in lightweight concrete. The only issue I have had with it is that it causes a flash set when used as an aggregate, but that is solved by mixing method.

[shuboyje]

Re: expanded clay

At least one Neapolitan builder uses them to insulate. I have no first hand experience, but have heard the insulation value of the resulting product is poor to non existent.

[david s]

Re: expanded clay

At least one Neapolitan builder uses them to insulate. I have no first hand experience, but have heard the insulation value of the resulting product is poor to non existent.

Because each grain contains lots of air I would expect it to be quite a good insulator, but do not expect it to be as good as vermicrete because it is a denser material. I might make some samples and do some tests.

[david s]

Re: expanded clay

Expanded shale is used in CMU over here as well as in lightweight concrete. The only issue I have had with it is that it causes a flash set when used as an aggregate, but that is solved by mixing method.

Thanks. Expanded clay is different to expanded shale. I haven't noticed it affecting setting, but the grains have a tendency to float presumably because water does not penetrate the outer shell too easily. I intend to try soaking them a bit first next time.

[Tscarborough]

Re: expanded clay

I don't think there is much if any difference. Clays are mostly shales, and the process is the same to produce them. In CMU the pellets are ground into a designed ratio of aggregate sizes, the aggregates used for lightweight concrete are also sized for the use. I have played with both. They flash set simply because they are so porous and extremely dry at the end of the production process. Obviously the finer they are ground the less this is an issue.

[david s]

Re: expanded clay

This may be of some use to folk following this thread, although I'm sure their claim of 11000 C must be wrong.(1100 surely)

Leca: The best light weight Aggregate for Thermal Insulated Concrete