I have recently bought a medium sized plot of wood/scrub land. Half of this plot was once used to dump shale from coal mines, which means I have a lot of shale.

I have been wondering/looking for possible uses for the stuff. One thought I've had is to make "mud bricks" however I can't find any mention of whether it is possible or not. I know the traditional method uses loamy soil but would it work with shale?

I don't have a kiln or any way of baking the bricks, so would be reliant on the sun. I was thinking maybe adding water and maybe some loam?

Aside: there are no suitable tags for my question and I do not have the reputation to add any, I'm thinking I could be on the wrong site for this question, if I am, please advise me of a more suitable one.

  • $\begingroup$ "Gardening and Landscaping" would be the alternative site. i suspect your problem is that the shale is too big to make bricks/etc with, but too small to build drystone walls with? $\endgroup$ – winwaed May 7 '15 at 13:03
  • $\begingroup$ I looked there but everything seemed more plant oriented. It's the science I was hoping to understand. The shale is like smashed slate so chunky bits around an inch diameter but a few mill thick but also a lot of nearly sand stuff which I could sieve if suggested. $\endgroup$ – Doug May 7 '15 at 13:13
  • $\begingroup$ I have to admit that I love this question. Hope that some geo-chemist can come up with a scientific correct and yet useful answer. $\endgroup$ – Tactopoda May 7 '15 at 15:44
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    $\begingroup$ Me too but the current answer covers much of what I was wondering :-) basically... Try and then try and smash it. $\endgroup$ – Doug May 7 '15 at 17:05

Your idea has merit. Shale is classified by geologists as being a mudstone. It is composed of silt and clay sized minerals.

According to this geology website, shales can be crushed to produce a clay and then mixed with water. These days, items that were once made from natural clay, such as terracotta pots and tiles for roofs, are now made from crushed shale.

Extra Information

One thing to be mindful of is that clays expand when wet and contract when dry. Anything you make from it, such as bricks, that isn't baked or protected from water by a sealed coating will expand and contract according to it moisture content.

Another application which you may want to consider is to supply crushed shale as a garden mulch or other such landscaping product.

  • $\begingroup$ So would you think sifting the shale for the sand and adding water (like a cement) would make suitably strong enough bricks to be used in constructing a shed? $\endgroup$ – Doug May 7 '15 at 13:30
  • $\begingroup$ Looking at that link shale is in fact used for cement with the addition of lime. Thanks for the answer :-) $\endgroup$ – Doug May 7 '15 at 13:33
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    $\begingroup$ @Doug Just make sure you have shale. During the 19th Century & into the 20th, shale was sometimes used to describe shale, slate & schist. I'll answer your additional question next. $\endgroup$ – Fred May 7 '15 at 13:42
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    $\begingroup$ Regarding sifting for sand & mixing with water to produce a strong product. It really depends on what minerals are in the shale as the composition of shale deposits global is not uniform; they each have their own differences. Do some tests on the material you have. Make some bricks and see what they turn out like. Try breaking them with a sledge hammer to get initial empirical indications of strength. Change the formula of the mix & when you have a product that looks OK, conduct a uniaxial strength test to see what sort of pressure will cause the brick to break. $\endgroup$ – Fred May 7 '15 at 13:53
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    $\begingroup$ Make 'em and smash 'em. My favourite approach. $\endgroup$ – mtb-za May 7 '15 at 22:18

Adding to Fred's answer, there are two points you have to take into consideration:

  1. Whether the "shale" is actually composed of clay minerals, or is it something else. You said it's what they took out from a coal mine, so it's probably crushed and milled.
  2. Assuming it is clay, there are some problems with that. As Fred said, clays expand and contract with water. Firing it solves the problem - it mineralogically changes the clays to other minerals that do not possess that characteristic. Now, there are clays and there are clays. Some can take in a lot of water (such as smectite) while others don't (illite).

I would suggest a simple experiment. Take a bowl, fill it with that stuff, soak it completely with water, and let it dry completely in the sun. Do you see any mudcracks in it? If yes, I would recommend against using it for construction without firing it.

  • $\begingroup$ The stuff is a light blue/grey colour if that adds anything to the discussion. I'll start an experiment at the weekend (if we get any sun) and update everyone here. $\endgroup$ – Doug May 8 '15 at 6:40

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