Cob, Adobe, Rammed Soil and Dry Stone as Construction Materials.

Calliban · 2023-11-27 16:29:11

Amazingly, I could not find a topic on these basic building materials in the life support section. But they are extremely relevant to construction on Mars. So I thought it would be worthwhile creating one.

Part 1: Cob

Cob is a building technique that has been used in England for many centuries. Clay and sand are mixed with straw and are used to build up walls by hand in layers. Some cottages made from cob are centuries old. In England, damp is a constant problem. Cob walls are built upon a damp proof layer of heavy stones. The structure is usually covered by an overhanging thatched roof. From a modern perspective, the value of cob is questionable. The main costs associated with building a house are labour. Why use a material that is weaker in compression and vulnerable to damp, when much stronger materials like baked brick and concrete are available and won't cost much more? This is why cob isn't used much anymore. Apart from the occasional garden shed.

On Mars, a number of things look different. Firstly, we are unlikely to have available large quantities of portland cement. We may be able to access liquid water and Martian regolith is essentially dessicated clay. The Martian surface is also very dry, which removes a significant problem for cob. Compressive strength of dry cob is about 1.2MPa. That is sufficient for quite sizable structures, especially if walls are tapered outward towards the base.
https://www.icevirtuallibrary.com/doi/a … n.22.00022

The straw provides tensile reinforcement and also prevents crack propagation. On Mars, we would need to either grow natural fibres to reinforce the cob or instead use a synthetic fibre. This could be something simple like shredded polyethlene.

For dome and tunnel structures that are relatively small, I wonder if we could do something even simpler and less labour intensive. Maybe we can cast structures out of wet mud? For a dome, we would create a formwork by inflating an inner polymer dome, within a second outer polymer dome. A wet clay produced by mixing fine regolith with water, would be poured between the layers. The outer dome will be permeable. The cast mud will rapidly dry in the thin, dry Martian atmosphere. Once dry, we deflate the inner dome and remove the outer. We now have a free standing dome made from dry mud. Next, we cover the entire dome with several metres of raw regolith. We paint the interior of the dome with lime, to provide a hard, impermeable inner surface. Next, we pressurise.

The strength of the dry clay material will be no more than a few atmospheres. This limits the size of the domes that we can produce in this way. But this method allows us to build habitable volume very rapidly. We simply inflate a double skin polymer dome, fill the gap between the layers with mud and let it dry. The polymer can be used over and over again. The only materials needed are regolith and water. It would be neat if we could find a way to recapture the water. Liquid water will not be an abundant resource unless we can find an aquifer. One way of doing this would be to make the outer polymer dome impermeable and the inner dome permeable. As the mud dries, the inner volume will fill with water vapour. We can run a compressor, which will compress the vapour back into a liquid for reuse. In this way, we coukd recover almost all of the water needed. So the only material we need in abundance is regolith fines, which are everywhere.

Last edited by Calliban (2023-11-27 16:56:28)

Calliban · 2023-11-27 17:19:04

Adobe is as ancient as cob and remains in use as a building material in dry climates.
https://en.m.wikipedia.org/wiki/Adobe

Adobe is unfired bricks, made from a mixture of clay, sand and water. Straw is sometimes added. The bricks are cast in moulds and are left to dry in sunlight. The resulting bricks are then bonded into walls with mortar made from the same material. Adobe bricks vary in compressive strength, but most US building codes specify a minimal compressive strength of 2MPa. On Mars, without the threat of damp or rain, walls should remain strong and free from erosion for centuries. Following the production of a cast mud dome, adobe bricks could be used to construct a central pillar, which would provide additional design factor against the weight of the overburden.

Internal walls could also be made from adobe. All water used in the manufacture of adobe can be recovered. On Mars, we will not have wood or abundant metals to make furniture for early settlements. Seats, tables, beds, cupboards and sideboards, could be made from adobe bricks and painted with lime or polished with wax. Stairways can be made from adobe, with stone paving. Floors will be polished stone, set in soil based mortar. Even sinks, baths and showers can be adobe, if sealed with an oil or wax. This suggests that we could built entire cities on Mars from little more than dirt, using endlessly recycled polymer formwork and water that is used again and again.

SpaceNut · 2023-11-27 17:35:15

Same mixture as brick which we do have but as far as building the structure after making them might not seem a possible first round building but if we can layer the mixture into a dome and build out from that we can build brick use into the continued expansion of the building. It is possible to build arches as well to create the central area as well.

Calliban · 2024-09-02 13:21:16

This dry stone dome architecture may be suited to Mars.
https://en.m.wikipedia.org/wiki/Trullo

No mortar or bonding cement in used in its construction. Just grade sorted rocks, arranged in a way to form walls and an enclosing dome. On Mars, the only necessary addition would be a few metres of regolith piled over the structure to counter balance internal pressure and provide a labyrinth seal keeping the air in. But this can all be achievedby sorting surface regolith into different sized components. The large rocks become structural elements. The smaller stuff gets heaped over.

This simple architecture has been recreated across Europe.
https://en.m.wikipedia.org/wiki/Cloch%C3%A1n
I have seen similar things in Scotland.

On Mars, it would be useful to make use of a pressurised reusable tent like structure, allowing humans to assemble the walls in a breathable environment. Alternatively, semi-intelligent robots couid assemble the walls for us, sorting the rocks and assembling them in the correct order. Robots could be uniquely suited to this task. They could build up a geometric map of every one of those thousands individual rocks, selecting the right one for each spot in the wall.

Last edited by Calliban (2024-09-02 14:24:49)

Calliban · 2024-11-08 08:27:15

Why we should build with stone again.
https://youtu.be/VVaWmEI9O1w?si=CxF-SIoXZi83faGe

Interestingly, some quarries are entirely electrically powered. The manufacturing supply chain for stone is much shorter than reinforced concrete, which requires several mined components. Natural stone is typically stronger than concrete as well. But unlike reinforced concrete, stone cannot take tensile forces.

On Mars, underground stone mines could be useful space. Whereas an open cast mine will require robotic or pressurised vehicles, underground can be a shirtsleeve environment. Also, the voids created by room a pillar mining, can be sealed off and used as habitation space. Mars appears to lack the large carbonate stone deposits that are necessary to make portland cement. Stone may ultimately be a cheaper option on Mars.

Calliban · 2025-04-17 17:13:41

Almost every image that I have seen of the Martian surface shows a landscape littered with rocks. Some of these rocks are pebble sized, whilst others are car sized. Rocks in this size range make up a large fraction of the mass distribution of regolith. With this in mind, I wonder if we could develop a machine that automatically scans individual rocks and then saws them into a number of predetermined shapes and sizes? Basalt blocks will be stronger than bricks that we can produce from clay. If thin stone tiles can be produced, then timbrel vaulting can be used to build multistorey structures.

Calliban · 2025-05-10 17:34:36

This article explains the science behind corbelling.
https://thestonetrust.org/master-class- … orbelling/

This is an ancient technique that allows structures to be made entirely from dry stone without mortar. This allows construction of walls, arches and the beehive stone houses built around the world and shown in the article and videos below.

https://youtu.be/OzeFlHGEM8I
https://youtu.be/mq0paONxodc
https://projects.mcah.columbia.edu/medi … sconst.htm

This technique was one of mankind's first construction techniques. It allows weather resistant structures to be made using nothing other than loose rocks, sorted and lightly processed to achieve the right shape.

This technique may turn out to be useful in construction on Mars. We face the difficulty that early structures must be imported from Earth at great expense, or made by processing local materials. Eventually, we will build structures from steel, glass and high strength materials like basalt fibre. But making these materials requires a great deal of equipment and energy, both of which will be expensive on Mars in the early days. Whilst clay is everywhere on Mars, bricks require both water and energy for baking. What if instead, we could use the abundant rubble that covers the Martian surface? We can build corballed structures that are covered in a few metres of regolith to keep the air in. This allows habitable structures to be made using only lightly processed Martian materials. The required rock grades can be obtained by sieving excavated material, which is then seperated into coarse rocks suitable for corbelling and everything else, which is heaped over the structures to provide overburden.

Historically, corbelled structures have tended to be quite small. The rocks used are irregular and are held together by gravity and friction without mortar. Large structures are more likely to become unstable, because point loads between rocks can crush the stone, resulting in slip and instability. However, if stones can be shaped by a limited amount of cutting, then much larger structures can be built.

On Mars, we would likely start by building small structures, which can be connected by corbelled tunnels built between them. This allows a base to grow incrementally. When the corbelled structures are covered with dirt to a depth of several metres, there is sufficient back pressure to allow addition of floors using timbrel vaulting. This involves glueing together tiles or thin stones with a mortar. This mortar could be made from Martian fine regolith with water added. Once the thin, curved tile vault is in place, we can create floors by covering the vault with fine, dry regolith, which is then compacted down to produce a flat floor.

Last edited by Calliban (2025-05-10 17:51:52)

tahanson43206 · 2025-05-11 08:09:41

The article at the link below describes use of adobe (with a modern twist) for new homes in Los Angeles.

https://www.yahoo.com/news/california-w … 00587.html

The article mentions the Iranian architect whose work has been mentioned in a number of posts in the NewMars archive.

Curiously, his name did not appear in the article.

(th)

Calliban · Today 04:37:02

The concept examined in this post is the use of diamond cutting discs, imported from Earth, to shape Martian surface rocks into thin tiles or bricks. These are then bonded using a native grout or epoxy glue to form parabolic domes using a timbrel vaulting technique. The practicality of this idea depends upon the local abundance of suitably strong rocks. Regolith will need to be excavated and grade seperated to extract rocks of the right size. These would then be cut to shape using diamond saws.

The exact lifetime of a cutting disc is difficult to estimate, as it depends upon the hardness of the material being cut. This site gives an estimate of 10 months, based upon 20 hours per week of cutting. This amounts to an 800 hour life expectancy.
https://support.hisglassworks.com/hc/en … Disks-last

The amount of stone cut in this time, is again dependant on hardness. This article examines cutting rates for rocks of different hardness. Basalt has a hardness of 6-7 on the Mohs scale, which is comparable to granite. This document examines cutting rates and wear for a number of rocks, including many granites.
https://www.nature.com/articles/s41598-024-54625-5.pdf

Cutting rates vary between 4.5-11.5m2/hr, with 8m2/hr being an approximate average. A single disc will therefore cut 6400m2 of stone surface over an average 800 hour operating life. I estimate that a single 300mm diameter disc will weigh 1.7kg, based upon this product and its specification.
https://www.toolstation.com/bosch-stone … 40807c63b0

Suppose we wanted to build a hemispherical dome some 30m in diameter. How much cutting would be needed? A strong timbrel domes could be built from three layers of tile or thinly sliced rock. The surface area of a 30m diameter hemispherical dome is 1414m2. All three layers would have 3x this surface area, or 4241m2. A single diamond cutting disc, weighing 1.7kg could therefore cut enough stone to build a 30m diameter timbrel dome. A 60m diameter dome would require some 4x as much cutting, or 16,965m2. We would need 2.65 cutting discs, weighing 4.5kg, to cut sufficient stone for this. Such a dome would provide some 56,549m3 of internal volume. This is over 50x the Starship payload volume.

The dome will have high compressive strength, but would be relatively weak in tension. To pressurise the dome, we must cover it with enough regolith such that external weight balances internal pressure. As regolith is graded to provide coarse rocks, the lighter fractions will be compacted into a berm around the dome, that rises as the dome is constructed. This provides a surface that robotic assemblers can use as a base as the dome is constructed.

The interior of the dome will be decked out and divided into compartments using a mixture of stone timbrel, adobe, rammed soil blocks and fine regolith mortar.

Last edited by Calliban (Today 04:40:49)

Calliban · Today 06:47:13

I hadn't considered laser cutting of stone. But the answer appears to be yes.
https://baisonlaser.com/blog/laser-cut-stone/

Fibre lasers appear to give the best results for low porosity rock like basalt. Lasers can cut stone surfaces to precise shapes with very clean cuts. This would be advantageous, as it allows the finished stone elements to be glued together using extremely thin veneers of epoxy glue. This has much higher strength than any mortar we can make from soil. But it needs to be imported from Earth. If we can use layers as thin a 10 microns, then 100kg of epoxy would be enough to glue together a 60m diameter dome.

The precision allowed by laser cutting opens a lot of other applications as well. We could use stone composites to make a lot of things on Mars.

Last edited by Calliban (Today 06:53:24)

Void · Today 09:17:45

I am sort of working backwards on this due to (th).

I would suggest that if you had a thick Aluminum Foil Liner you might finish the interior of your stone domes. Sounds flimsy, but if the Stone Buildings are weighted down enough then a liner of that sort might be OK. I am presuming you could weld and/or glue this Aluminum Foil into a complete covering able to be air tight. And you probably would want something like a fire extinguisher, that could spray a sealant to plug an accidental leak.

Anyway a liner of some sort also might be of poly perhaps. Of course, Poly might burn.

The LEM, as I recall had walls that were very thick Aluminum Foil in thickness.

Ending Pending

Calliban · Today 10:26:41

Void, insulation of some kind may be valuable. Even with several metres of regolith covering the dome, the temperature difference between the inner and outer surfaces could result in substantial heat loss. And power won't be cheap on Mars. A lot of energy will be needed just to establish a thermal gradient across the regolith berm.

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#1 2023-11-27 16:29:11

Cob, Adobe, Rammed Soil and Dry Stone as Construction Materials.

#2 2023-11-27 17:19:04

Re: Cob, Adobe, Rammed Soil and Dry Stone as Construction Materials.

#3 2023-11-27 17:35:15

Re: Cob, Adobe, Rammed Soil and Dry Stone as Construction Materials.

#4 2024-09-02 13:21:16

Re: Cob, Adobe, Rammed Soil and Dry Stone as Construction Materials.

#5 2024-11-08 08:27:15

Re: Cob, Adobe, Rammed Soil and Dry Stone as Construction Materials.

#6 2025-04-17 17:13:41

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#7 2025-05-10 17:34:36

Re: Cob, Adobe, Rammed Soil and Dry Stone as Construction Materials.

#8 2025-05-11 08:09:41

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#9 Today 04:37:02

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#10 Today 06:47:13

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#11 Today 09:17:45

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#12 Today 10:26:41

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