Stabilised rammed earth

[Anonymous]

Looks like a really useful technique, anybody know anything about it or seen any examples?

http://www.earthstructures.co.uk

[J3 Building Futures]

I entirely disagree.
There is no good reason to stabilise Rammed Earth. Rain will slightly erode unstabilised RE, but only to a small degree. The picture below is a good example, its an athletics track in either Switzerland or Austria, and you can see slight degredation just below the top ringbeam ( this was after 2 years)

In Australia, they use up to 10% cement, which is only a few percent less than a concrete wall. In short, a ton of cement means a ton of CO2. RE is approximately 2.2 tons per m3 and ,therefore, a wall 300mm thick, 2.4m high and 6.2m long uses a ton of CO2 in the cement production alone

All SRE does is to substitute subsoil for aggregates and sand.

The strength argument does not make sense either.
I have built test columns that were 350mm2 and 3m high. After 1 month, they were subjected to compression testing and failed at 10.4 tons. Even id astructural engineer, unfamiliar with the technique, imposes a safety factor of 6, normal RE will comply.

The only reasons to use cement are:
i) if you are building with no foundations, where capillary and rain splashback action can have serious effects. Then you might add cement up to the splashback height.
ii) if your earth contains insufficient quantities of clay. (5-20% of the RE constituent should be clay- more and the wall will crack during its 'curing' time, less and it will not have sufficient binding qualities)

For perfect aesthetics, yes you need an overhang, but the most important thing is to ensure that the wall remains dry during the first month. Optimum moisture content of a new wall would be 10-15%, depending on the properties of the earth being used. After a month this will fall to about 4-5%, which is its optimum strength level. Any rain ingress may penetrate to 100mm maximum and will then be breathed out as the wall dries again.

Hope thats a useful counter

[Anonymous]

Jason that's really useful, yes I would love to see photos.

Our soil is likely to be around 20% clay with a fairly high aggregate content.

The factors that worry me with regards to URE are:

1. Most of the rammed earth wall will be in direct contact with soil, the house is earth sheltered to it's N face. That appears to necessitate some kind of impermeable barrier between the wall and soil.

2. What happens if we get monsoon rain when the walls are supposed to be curing? We had a couple of months in late summer/early autumn last year and again through winter.

3. Internal surfaces will need some kind of render, according to the blurb SRE doesn't, it kind of appeals to me to have the fabric of the wall visible

Thanks very much

[Anonymous]

We're at an early stage with the design so foundations etc still have to be dealt with. Will bear all the above in mind. Many thanks for your time.

[J3 Building Futures]

Very welcome, be glad to help further if needed

[Anonymous]

If you drop me an email (in members profile) I will send you some photos, the attachments allowed arent big enough here

Email sent

[Author]

Posts