Brick

Starting from Martian clay or other materials, a brick-maker can create a wide variety of structures and paved surfaces as well as furnaces and ovens for smelting, blacksmithing, glass-blowing, cooking, etc. The brick-making craft requires only other small-scale crafts for its equipment (blacksmithing for its iron tools), thus qualifies as a small-scale craft suitable for a frontier town (small and largely self-sufficient) economy.

Due to the 1/3 gravity, structures made out of brick can be much larger than on Earth, yet still hold up under their own weight and be easy to transport. However, due to the internal pressure required for most martian buildings, brick construction that also has to withstand pressure requires a separate air tight bladder structure or substantial reinforcements.

Material

Brick

The brick can be made from regolith, plastics, fiberglass or composite materials. Regolith can be sintered at high temperatures. A mixture of molten plastics and regolith powder can be produced at moderate temperatures. Bricks can be made stronger by having fibrous material in them. (e.g. ancient bricks were mixed with straw.) This could be plant stalks, plastics, glass fibres, etc.

Mortar

Bricks can be piled up 'dry', as often seen in civil works. Bricks are also often uses in thin layers held in place with mortar, generally a form of cement. Portland cement may not be possible on Mars, so a substitute would need to be found. Sulfur cement is a possibility, as are other types of cement. Brick molds can be used to create interlocking shapes that can provide some strength without mortar.

Brick Structures

Bricks stand up well to forces that push them together (compression) but the mortar (if any) is weaker, and brick structures do not stand up well to sideways forces (Shear) and do not work at all in tension. Building a brick structure on Mars, where the inside is pressurized is problematic; the force created by the air pressure, would break the walls. If you want to have pressurized brick structures, either the air must be contained some other way (e.g. in an inflatable structure) or enough weight must be pressing down to keep the structure stable.

Estimates of 6.5 meters of dirt above the structure would be safe. (If the Mars base used 40 bar rather than 100 bar air pressure, this weight could be reduced. Only 2.5 meters would be needed.) See "The Case for Mars" page 191 for more discussion on this point. Note that 6.5 meters of dirt above colony structures would provide excellent radiation protection. Although the structure might resist the pressure, it would be subject to problems from humidity and freezing in the brick and mortar, unless a humidity control membrane, and perhaps insulation, was added.

It is probably more effective to use brick only in the construction of radiation protection structure around independent pressure resistant airtight structures. The brick structures would then be only in compression. Bricks should be highly resistant to windblown erosion, and as there is no rain there will be no damage from water or freezing, the main enemies of brick on Earth. Bricks could also be used for construction inside larger pressurized structures, as they are non combustible and can be used in the same ways as for traditional construction methods on Earth. Using sulfur cement inside the habitats would negate their fireproofing characteristics, so is probably not a good idea.

Brick Manufacturing

Pressure

Bricks can be made using only pressure and drying. It all depends on the source material, and exact methods will depend on what is available on Mars. "In fact, the UC San Diego engineers were initially trying to cut down on the amount of polymers required to shape Martian soil into bricks, and accidently discovered that none was needed. To make bricks out of Mars soil simulant, without additives and without heating or baking the material, two steps were key. One was to enclose the simulant in a flexible container, in this case a rubber tube. The other was to compact the simulant at a high enough pressure. The amount of pressure needed for a small sample is roughly the equivalent of someone dropping 10-lb hammer from a height of one meter, Qiao said.

The process produces small round soil pallets that are about an inch tall and can then be cut into brick shapes. The engineers believe that the iron oxide, which gives Martian soil its signature reddish hue, acts as a binding agent. They investigated the simulant's structure with various scanning tools and found that the tiny iron particles coat the simulant's bigger rocky basalt particles. The iron particles have clean, flat facets that easily bind to one another under pressure."

Heating

Bricks on Earth are usually made by baking in kilns. Different temperatures give different results. Higher kiln temperatures give more water proof bricks, which may not be very useful on Mars.

Embodied energy

Different types of brick require different amounts of energy to produce.

Materials	Embodied energy (MJ/kg)	Density (kg/m3)	Production
Compressed Regolith	0,5	2000	Regolith compressed and combined with some form of cement
Clay Bricks	2.5-3	2000	Martian clay baked and fired
Plastic blocks	80-100	900	Plastic from biomass or CO2+hydrogen reactions
Glass blocks	15	2500	Silica, cleaned and with required additives
Sintered regolith	1.5-3	1500-2500	Regolith heated till some melting creates structural links

See Also

Universal bricks