Yesterday’s video about How the Pyramids Were Built shows how loose limestone can be turned to stone. This method seems easier and simpler than using MICP, don’t you think?
This seems like a good time to experiment with geopolymer cast stone to make the first ever earthbag stone dome. The mountain range near our home is predominantly limestone, so the main material is readily at hand. I recently tracked down a supplier and am in the process of obtaining materials to make some test bags.
The ancients had to make the soil binding materials from scratch using salt, wood ashes, etc. But now the basic ingredients (sodium carbonate and lime) can be purchased off the shelf and mixed with limestone and water. In fact, the process is so simple that I’m surprised more people are not investigating the process.
The end product is actual stone, not just something “hard as rock”. It would be fire and rot proof, bullet resistant (almost bulletproof at some point after it gains hardness), totally waterproof obviously, and could possibly last thousands of years. Not much else can compare to this. Even modern concrete falls way short, because it’s too brittle. Concrete has a lifespan closer to 50-100 years in most cases (I’m talking about lifespans of actual structures, not some theoretical time period). The next closest thing might be Roman concrete that was used to make the Pantheon in Rome, among other structures. More about Roman concrete here.
Alternate title: How to Build an Earthbag House That Will Last as Long as the Pyramids. I can’t say for sure that the pyramids were built this way, but this video describes a reasonable theory of how the blocks of the pyramids were made with natural materials from the Giza Plateau – limestone, kaolin clay, sodium carbonate, lime and water. According to the video, the mixture consists of 95% limestone aggregates, 5% rock making binder and between 12%-17% water. The same methods could be used to create rock hard earthbags with incredible durability. And it’s simple enough that anyone can do it. It’s ancient technology after all.
There’s a great deal of very interesting information about this by Professor Joseph Davidovits and other researchers at the Geopolymer Institute. Here are a few quotes from their Archeology page.
“The pyramids stones are man-made (synthetic, artificial), cast in situ.”
“The Great Pyramid of Kheops is comprised of about 2.5 million blocks, most weigh two tons and could have been hauled by no less than sixty men. But some weigh up to seventy tons and these are to be found, not at the base of the pyramid, but some forty meters high. Since the ancient Egyptians did not yet have the wheel, they would have needed more than two thousand men to haul each block.”
“How could the Ancient Egyptians have cut these stones, which are extremely hard, with only the most primitive of tools? At best they would have been able to use copper saws, and copper is a softish metal, incapable of hewing the hard limestone blocks from which the early pyramids are constructed.”
“If the stones were carved, as most people believe, where are the fragments of broken stone left over? Limestone frequently splits on being cut. 5 million tons of limestone blocks must have produced millions of broken blocks and fragments. Yet, not a trace of them has ever been found.”
“The pyramid casing stones are light in density and contain numerous trapped air bubbles, unlike the quarry samples which are uniformly dense. If the casing stones were natural limestone, quarries different from those traditionally associated with the pyramid sites must be found, but where?”
“In natural stones, we expect to find elements that had the time to crystallize. However, silicates in pyramids stones are completely amorphous (not crystallized). This allows us to think that we are in presence of a cementitious process. The silicates were formed in a very short period of time.”
“This photo shows a sample of the casing from the ascending passage of Kheops great pyramid… the cross section is characterised by the presence of organic fibers and air bubbles that do not exist in normal situation, especially in a 60 millions years old limestone from the eocene era!”
“Barsoum’s team took a fresh look at 15 samples using scanning- and transmission-electron microscopes. The samples contain ratios of elements, such as calcium and magnesium that do not exist in nearby limestone. The imaging also revealed regions of amorphous structure. Both observations suggest that other substances were added to make a concrete mix.”
“The famous Massachusetts Institute of Technology, Boston, USA, is supporting Prof. Davidovits’ re-agglomerated stone (concrete) pyramid theory. At MIT, Professor Hobbs and two colleagues and students are experimenting the construction of a small scale pyramid using the method recommended by Davidovits.”
This video helps explain the geopolymer process. In this video Professor Davidovits explains how they made a man-made sample of re-agglomerated stone and then submitted it for laboratory analysis. The laboratory said it was natural stone. For more details, go to the Geopolymer Institute YouTube channel http://www.youtube.com/user/kadamix to see more videos such as: Bricks made at low temperature, low energy, low cost http://www.youtube.com/watch?v=zjeVeDVtghc&feature=related,
If the microscopic, x-ray and nuclear magnetic resonance spectroscopy analysis doesn’t convince you, think about the Colosses of Memnon, which these same geopolymer scientists believe were cast of amalgamated/agglomerated stone in a similar manner as the pyramids using geosynthesis (limestone treated like a concrete).
“In antiquity, the statues commanded respect; the Colosses of Memnon are monoliths: they are made from a single block of stone weighing nearly 1000 tonnes and standing on a pedestal of 550 tonnes. They are 20 metres high, equal to a seven storey building. The stone from which they are made is quartzite, which is practically impossible to carve.”
“None of the great quartzite blocks bear any trace of tools that is so common in the sandstone and granite quarries: a material that is so hard, so refractory in the face of sharp tools cannot, it is true, be worked by the same methods as ordinary sandstone nor even of granite. We know nothing of how the blocks of such a rock were squared, how their surfaces were dressed or how they were given the beautiful polish that can still be seen in some places… Did the sculptor, in the middle of engraving a hieroglyphic character, strike one of the flints or pieces of agate that are encrusted in the material, the line of the character continued in all its purity, and neither the agate nor its enveloping stone bear the slightest crack.”
Summary: Whether or not the pyramids were made with geopolymer cast stones could be debated endlessly. However, the key point for natural builders is geopolymer scientists have developed recipes using natural materials and simple production techniques that can be utilized in rammed earth and earthbag construction. This is an exciting new field of opportunity in my opinion. Please refer to the publications by Professor Joseph Davidovits and other researchers at the Geopolymer Institute for complete information.
Here’s a natural substitute for steel rebar. It seems like this material would work perfectly with earthbag building, especially in seismic areas where additional reinforcing is typically required. Image and content below is from the Smarter Building Systems website.
“Zeebars Basalt Rebar is an alternative to steel and fiberglass for reinforcing concrete. Made from volcanic rock it is tough, stronger than steel and has a higher tensile strength. Much lighter than steel, 89% percent in fact! One man can easily lift a 500 foot coil of 10 mm rebar.
Zeebars are naturally resistant to alkali, rust and acids. Moisture penetration from concrete does not spall. Zeebars need no special coating like fiberglass rods. The same thermal coefficient expansion as concrete!
Allowing thinner, lighter panels and decks, Zeebars reduce the thickness and spacing between the rods and the concrete and surface. Much more flexible design! Smaller rods allow for more critical spacing and designs. Zeebars are easily cut to length with regular tools.
Basalt rebar does not conduct electricity or induce fields when exposed to RF energy, great for MRI or data buildings. Zeebars are perfect for marine environments and chemical plants where corrosion is a continuous concern.”
The subject of sun tubes or solar tube skylights keeps coming up in email exchanges with readers, because they’re often more efficient than conventional skylights. There are numerous competing brands and designs, but the basic concept is a skylight that directs light through a mirrored tube. Some designs like the Solatube skylight pictured above bend around obstacles. Some have flexible pipe, and some have one skylight with multiple tubes that direct light to different rooms.
Go to Google Images and search for “sun tube skylight” and you’ll see lots of options. This is a great way to add extra light to areas where windows are not practical.
Google Images
(If the link doesn’t work, just go to Google.com and click on Images.)
Compressed earth blocks (CEBs) have countless uses and come in dozens of shapes (many more than shown here). They are commonly used for residential and commercial structures, earthquake resistant structures, privacy walls, columns, bond beams, pavers, planters, stairs, etc. For instance, you could make CEB columns on your house and privacy walls and stack earthbags between. (See Confined Earthbag.) Right now I’m making an outdoor oven with CEBs. The possibilities are endless.
Star Top Construction and Blockprasan Co., Ltd. manufactures very high quality compressed earth block presses in Nakhon Pathom, Thailand. When you look at the ¾” (2 cm) thick steel parts, it sure looks like these machines would last well over 100 years with continual use. Note: I am not paid in any way for promoting these presses. I’m very impressed with their ruggedness and quality and would like people to know about their products. In fact, I’ve admired them for about 4-5 years and have finally got around to telling people about them.
Many people know about the Aureka presses made in India. Here’s a brief comparison:
Star Top Standard press makes 10 types of blocks and costs $800 US.
Star Top Hitop press makes 30 types of blocks and costs $900 US.
Aureka 3000 multi-mould manual earth block press as shown here costs $X [cost not available yet, but it’s roughly twice the cost if I remember correctly]
Star Top also manufactures a whole line of block making equipment, including hammermills to pulverize soil, mortar mixers to mix the soil with cement, and machine and hand-operated block presses. I’m guessing there are several thousand small shops in Thailand with a similar set of machines. They quoted us $4,171 for the whole set of machines to make blocks by hand and $8,843 for the machine operated set that makes two blocks at a time.
Sample CEB Block Shapes (many more available)
Note the holes in the CEBs. Rebar is inserted through the blocks and then the holes are filled with cement grout. There is no mortar between this type of CEB.
Star Top website Star Top Technology
Phone in Thailand: 034-2679534
Email: startop@blockprasan.com
Cost of CEBs at Phu Phan Research Center: 23 cents
Standard size of CEBs: 12.5x25x10 cm high (you can make other sizes)
Update: This video shows how the press works. It’s actually a competing brand made by K. Thai Machinery Company that looks and operates virtually the same way.
Sometimes special hardware can really come in handy for speeding construction. That’s probably why there are hundreds of different anchors and straps available – they really do make buildings stronger and easier to build. The anchors pictured above are used to build hogans, an octagonal shaped structure favored by the Navajo and others living in the American Southwest. These anchors would be useful for building an octagonal post and beam structure that could be wrapped with earthbags. You could build an octagonal earthbag structure without a post and beam frame, but it does open up some interesting possibilities such as:
– building insulated earthbag homes with scoria, etc. [the frame would help stabilize the walls]
– helping obtain code approval [not a sure thing, but it may help in some cases: you could say the bags are for insulation]
– providing the aesthetics of post and beam
– enabling the roof to be built sooner, which would provide shade and protection during construction [think through how you will build the earthbag wall: Wrap the frame with insulated bags? Finish the roof immediately above the earthbags later so you can tamp the bags?]
– building fast, low cost accessory structures such as sheds, gazebos, workshops, etc.
This is a follow-up blog post to my previous post entitled Fastest Corner Pinning Method? I’ll keep it brief. I just wanted to provide a close-up photo of the final pinned corner. (Click to enlarge.) You can see how simple this method is. Just poke sharp galvanized wire (about 16 gauge) through the folded corner of the bag and bend the ends of the wire together. Do this during breaks and you’ll have a whole pile of bags ready in almost no time since each corner takes just a few seconds.
Here’s the same video on my YouTube Channel if you missed it the first time.
You can adjust the moisture in your soil mix. In this case we’re using road base. You can see that this is too wet. If it looks glistening with water then it’s obviously too wet. If you squeeze it and see water coming out like this then it’s too wet. So you can take your digging tool – this is a grub hoe – you can mix drier soil with it until you get the right mixture. This is perfect right here. Let’s zoom in and take a good look at this. It has just enough moisture that when it’s tamped together it will turn into a hard block – a hard building block – and water won’t squish out of the bags.
Note: I look at every bucket of soil before dumping it in the bag to make sure the moisture content looks good. Sometimes the worker filling buckets makes a mistake.
Some people are using sharp rocks, thorny vines, etc. to prevent slippage between bags. These things may help a little, but barbed wire does a lot more than prevent slippage –– it adds tensile strength to your structure. This point is often overlooked. Tensile strength restrains courses of domes from moving horizontally (expanding outwards from the weight above). Tensile strength also helps hold corners of buildings together. For instance, over time a corner could separate as the walls of a structure lean in different directions. But proper use of barbed wire between courses would help prevent this from happening.
Cheap and easy compressed earth block (CEB) floors
Here’s a great, low cost way to build floors with compressed earth blocks. This Instructable is by Velacreations. Visit their website for more great ideas.
When considering what material to use for a floor, few people look beyond a concrete slab, with something like tile or carpet as a finish. For us, however, there were several factors that made a stabilized compressed earth brick (SCEB) [or just CEB for short] floor far more appealing, including cost, skill, and time required.
Earthbag Building Blog 