Rammed Earth Walls

Discussion in 'Designing, building, making and powering your life' started by TLP, Sep 27, 2014.

  1. TLP

    TLP Junior Member

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    Hi all, I been playing around with some small test blocks of RE. Mine look like a solid color. I was wondering if anyone knows how to get the striations. I read iron oxides are used so I checked a local pottery shop that sells them. Price will range from $7/lb. (e.g, red or black) to $10/lb. for red or orange. I got no idea the cost for all the walls in a 1500 square foot house. https://www.masoncolor.com/pigments/pigments.asp

    We are investigating the MSDS, one has chromium a known toxin. Some paint pigments use iron oxides with toxins. Just wondering if anyone has more natural lower cost ideas and if anyone knows the technique to get those beautiful striations. All I can think is sprinkle the power to the form side as I tamp, but some look like they crawl up and down the walls in certain areas. I attached some pics, you can see what I mean.

    My sample is still wet, just pulled the forms, it may lighten a little.
     

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  2. TLP

    TLP Junior Member

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    So far I have used no cement to stabilize the soil, just clay-silt, 3/4 limestone, and sand. I am also wondering how they get the wall so smooth?
     
  3. sweetpea

    sweetpea Junior Member

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    I've always wanted to try this.

    This ratio of sand to clay (70/30%) might make it easier to find colored sands, at a local rockery, that they use for paths. Here we have lots of tans and yellows and ochre colors.

    "Clay/sand ratio has the greatest contributing effect on how well an earth wall will perform. Traditionally, for raw rammed earth, that ratio has been established as 30% clay and 70% sand. "

    https://rammedearthworks.com/page/Blog


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    This guy lined his forms with sheet metal and got smooth walls:

    https://www.motherearthnews.com/diy/rammed-earth-house-zmaz73sozraw.aspx?PageId=2

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    This talks about making sample blocks first:

    https://rammedearthworks.com/page/Services/Soil_evaluation_and_mix_design_formulation

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    These pictures look like, even though the soil is not dramatically different, there are variations and textures that happen:

    https://rammedearthworks.com/page/Projects


    Would love to see pictures of what you come up with :)
     
  4. TLP

    TLP Junior Member

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    Thanks for the info sweatpea I'll study it. I am familiar with SIRE and am currently reading David Easton very good book "The Rammed Earth House". I was anxious to try some sample blocks, perhaps he gets into the striations later. I have not read his formwork section yet but the sheet metal sounds good.

    He calls for 30 clay to 70% sand/rock. My first attempt was 100% clay just for experience and learning. Of course it stuck to my shovel and 2x6 rammer, no good, fell apart. So I added 70% sand (see pic) no good broke when I removed the forms in 24 hours(pic 1). So I got some limestone, 3/4 cream about 30% same for sand rest clay, held up better, in 36 hours did not look very strong, easy push over when dry, low compression and shear wall strength(pic 3 and in the OP). Mind you tho, this is a 3" thick sample, not 24" normal wall. I'm going to add some pozzolan cement around 10% see if drys faster and gets stronger. I'm using OSB forms and I can see the dirt on them that got pulled due to not being dry which I think made the wall rough. I do not want to be waiting more than an hour to pull my forms and keep building walls. I'll try it today let you know how it goes. If I can get the tornado strength and speed I want that be a start. My rock quarry only has cream colored sand, colors sounds like it be worth a try I'll look around.

    My soil jar test pic is attached I am getting it from top soil harvest a local farmer brings to the quarry. It is hard to see but the clay and silt content are about the same ratios. Anyone know how to tell what type soil this is? Ball or Bentonite? I've read Composition of Kaoline varies from 20-80%, 10-25% mica, 6-65% quartz, has alot to do with adhesion. I guess I'd need to take it to a lab to find out, which I will later to comply with code once I think I have something strong enough to spend that money on. AT least I'm not shrinking real bad yet and cracking from wet to dry. I really want high clay content so my walls regulate indoor humidity, and smell natural, but so far my clay does not appear to be that strong that is why I am stabilizing it with cement.
     

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  5. Ligeia

    Ligeia New Member

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    How is your sample wall holding up today? Do you expect that extreme climate change (e.g, freezing temp) may subject it to fissure or fault?
     
  6. TLP

    TLP Junior Member

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    I added around 20% fly-ash type c to my last mix and it looks much strong but I developed a crack when I pulled forms in a hour. Look like it dried faster too, so I'm thinking I got a shrink crack or I need more cement. Surfaces looks MUCH smoother. Amazing what a little cement can do, and it looks more homogeneous and getting closer to aesthetically pleasing. Also, when I dumped it over to get a feel for shear or impact resistance I see bigger blocks, when I pressed down by hand it felt like concrete compression strength. A real challenge keeping the clay content up & density low by not using portland cement, but struggling to get a good binder.

    Ligeia: Good question, I had not thought that far ahead yet but, I'd imagine like roofs the darker the more solar gain, the less freezing. It will depend on the surface moisture content I end up with based on density, and how permeable. Clay has a high surface storage area which works great in humid summers, but can freeze and heath causing cracks in winter. I can add alot of portland cement and toxic add mixes to get my density up, then shifting/settling causes cracks due to low plasticity. I read here below that lime will help, so I'll add some hydrated high calcium type n comparable to NHL 2.5. Think I'll go get some quarry grey limestone screed today which is the rock deeper in the ground around here they screed down. It has a lot of fines and small rock I can use in conjunction with cream sand at the surface for striations test next.

    So my next mix in a day or two percentages I'm thinking will be,

    15 clay, 15 fly-ash-lime, as binder.
    40 % 3/4 limestone, 30% sand.
    Art surface filler: cream sand, grey limestone

    By the way, once I work out the bugs my plan is to build a test landscape retaining wall 24" thick and see how it does this winter before a home next spring. We get down to around 10F, with wind chills 10 below sometimes in USA, Z5. I'm casting in fall right now, mild 80-85 F, 40% RH.

    https://trid.trb.org/view.aspx?id=308525
    https://trid.trb.org/view/308524

    Any thoughts or better ideas let me know.
     

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  7. 9anda1f

    9anda1f Administrator Staff Member

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    Your experiments will pay off TLP, honing in on just the right proportions for your ingredients. I've stabilized our 90% silt soil with portland cement at a 20%/80% ratio with good, solid results taking pains to ensure there was only very slight moisture in the silt prior to mixing and tamping. This is going from what I know about concrete ... that minimizing the moisture maximizes the strength. I'll be trying only lime as binder next spring when the experiments continue, basing it on lime mortar proportions.

    For the oolor striations, have you tried mixing your batch then adding the colored ingredient last and only slightly mixing it in? This might give the color gradients you're looking for.
     
  8. eco4560

    eco4560 New Member

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    Oh my - I have just replaced rendered straw bale walls in my dream house build fantasy with these…. They are beautiful! And everyone has earth, but not everyone has straw and clay….
     
  9. TLP

    TLP Junior Member

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    Getting there

    I ended up using a type s lime white oxide, or NHL 3.5 since it had more magnesium cement in it, fly ash, soil, limestone, sand in equal portions by volume. I got some different colored sand and crushed lime stone and added it as I rammed up courses. Threw some lime (white powder) toward the top, not sure that was a good idea I want white :)...problem is the small fines on the surface brush off easy. I think I need a sealer, I have one in a file somewhere that is not toxic. Anyone got any ideas?

    9andaif: For the oolor striations, have you tried mixing your batch then adding the colored ingredient last and only slightly mixing it in? This might give the color gradients you're looking for.

    Yes, worked alot better...difficult to just add to surface in my little 3" block but I can see this working if i seal it in.

    I think my through bolts are causing the cracks when I try and back them out and I can't ram the ends, so I'm not worrying about them. I'l have much better forms when I get serious :)
     

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  10. TLP

    TLP Junior Member

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    Getting there

    I discovered the beauty of iron oxides. I think when my walls are bigger and thicker they will look better. Left one is still wet, rained today, hard to get a dry mix and pull forms fast...this is after 3 hours rained stop. Others I pulled in 1 hour. I can see the art part takes some practice, adding color to the loose of pack fill changes it. :)
     

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  11. TLP

    TLP Junior Member

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    Sealer?

    The surfaces have some fines that are not very abrasive. I tried linseed oil (bottom of end) it darkens the wall quite a bit, and a water based acrylic concrete sealer not as dark but still unacceptable. Any ideas on a sealer?
     

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  12. sweetpea

    sweetpea Junior Member

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  13. TLP

    TLP Junior Member

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    Finally got my first test wall done, lots of work, getting ready to do more...not as easy as I thought but very rewarding.
     

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  14. songbird

    songbird Senior Member

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    sorry not to have seen this sooner, but have you tried to source white portland cement? it is used in flooring and tile work for grout (with silica sand), that's about as white as you could want. i'm not sure what the proportions of the mix might be (it's been many years), but you should be able to find something on-line (and perhaps if you need to add some lime for certain applications)...

    various colors are not too hard to find as pigments, look for terrazzo supplies if that helps. that may lead you to find aggregates of different colors. terrazzo floors are wonderful works of art in themselves.
     
  15. TLP

    TLP Junior Member

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    Yeh songbird I learned the hard way if you want complete control over color all cement and aggregate has to be white....Now finding them locally in large quantities to build homes will be the challenge...The soils we have here are all brown top soil I used (weak), brown-grey sub, brown-yellow below that. I'll try again and use more white cement I did find....I had to stucco that wall to hide all the issues. So far I like it, it looks better in person, my son does not judging off pics...

    Even if I add cement say 30% the surface will never be as hard as stucco. I don't get how these guys get a hard surface and all these colors and beautiful striations, yet :)
     
  16. TLP

    TLP Junior Member

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  17. Curramore1

    Curramore1 Junior Member

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    TLP and others, please correct me if I am wrong, but the more cement powder added, the better the water sealing of the wall?
    I know that concrete tanks are sealed by a higher cement : sand and aggregates content with no other sealer to keep the water contamination to a minimum. Been playing around here too, my soil is OK for RE but needs too much cement added to be economically viable, works out cheaper in the long run for me to buy in local Bracalba Quarry at Wamuran deco granite from 60 km away for my walls than to use my own. Sort of goes against the grain of being self sufficient and using your own resources doesn't it? But is more sensible financially in my case. How thick are you making your walls? Mine are 300mm. Also have tried a local soil/deco granite mix, but still abetter wall with just the deco, pity.
    Thanks for sharing your trials TLP.
     
  18. Curramore1

    Curramore1 Junior Member

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    TLP, I find that if I use a pneumatic vibrating rammer instead of a hand rammer and an ever so slightly wetter mix the smaller particles come to the outside and give a shinier appearance, also my forms have a smoother finish from the marine ply surface being so shiny. You could also probably sand it and seal with a silicon or poly finish. Different metal oxides from the shop added to the brew is all for the colours. You could probably try different natural plant pigments but they would biodegrade and fade pretty quickly I imagine. Still an experimental newbie myself still on the discovery path.
     
  19. TLP

    TLP Junior Member

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    C- I tried several different mixes, 30 % clay, 35 sand, 35 limestone 3/4.....friable surface, dirt wash off with a light spray hose....so I added fly ash and lime about 30% little better but still.....so I added portland cement thats when I noticed an improvement at the surface but still not good enough. Now for a binder, I'm thinking 70 % white cement, 30% brown clay that will make up 50% of my mix, the other 50 sand and rock. Hopefully my iron oxides change the color, it's not easy trying to change the mix....I tried a pigmented lime-cement at the surface that is too much work mixing and placing it.

    Problem is the more I cut back on soil the more I loose it's benefit, moisture management and breath-ability...last thing I want is commercial concrete I might as well pay to pour.

    What do you mean by marine finish on your forms?

    OSB I used is not the best, I was thinking metal for homes.

    I found some surface sealers specifically for RE in Europe, non here in the USA: I had to spray on a lime wash to even get a brush to not take off soil to put it on. There are some sprays I could use if I get a decent non-brown wall.

    Yes I tried 300 mm (12 inches)...I put a heat source on the wall with a 50 F temperature difference and it did not thermally bridge, so I don't think I need a foam core some are doing.

    There are VOC free paints that may be cheaper. I got iron oxides at a ceramic shop I dilute with water but, if I have to use a gallon per course to fight off browns and tans in soil, sand, rock, may be more economical to use low voc paint off the shelf...they are usually pigmented with iron oxides some of which have VOCs.

    Soon as I get this figured out and I like it I'm investing in rammers and will use skid steers to build homes, forget the shovel my back is killing me ;(
     
  20. Curramore1

    Curramore1 Junior Member

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    View attachment 2869
    TLP, the marine finish on the ply is a black, shiny and smooth finish on both sides of the ply. You can oil the forms too to make them not so sticky. I have seen a water whip style device used to lift the buckets of mix up as the wall gets higher, the pro's use a sort of conveyor belt. The pneumatic rammers require a fair horse of an air compressor to run them and they cost a packet to hire each day over here. I would love to have a bobcat too, so useful.
     

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