Lunarcrete
Encyclopedia
| Compressive strength Compressive strength Compressive strength is the capacity of a material or structure to withstand axially directed pushing forces. When the limit of compressive strength is reached, materials are crushed. Concrete can be made to have high compressive strength, e.g... |
39–75.7 N/mm2 (MPa Pascal (unit) The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre... ) |
|---|---|
| Young's modulus Young's modulus Young's modulus is a measure of the stiffness of an elastic material and is a quantity used to characterize materials. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. In solid mechanics, the slope of the stress-strain... |
21.4 kN/m2 |
| Density Density The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight... |
2.6 g/cm3 |
| Temperature coefficient Temperature coefficient The temperature coefficient is the relative change of a physical property when the temperature is changed by 1 K.In the following formula, let R be the physical property to be measured and T be the temperature at which the property is measured. T0 is the reference temperature, and ΔT is the... |
5.4 × 10−6 K−1 |
Lunarcrete, also known as "Mooncrete", an idea first proposed by Larry A. Beyer of the University of Pittsburgh
University of Pittsburgh
The University of Pittsburgh, commonly referred to as Pitt, is a state-related research university located in Pittsburgh, Pennsylvania, United States. Founded as Pittsburgh Academy in 1787 on what was then the American frontier, Pitt is one of the oldest continuously chartered institutions of...
in 1985, is a hypothetical aggregate building material, similar to concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
, formed from lunar regolith
Regolith
Regolith is a layer of loose, heterogeneous material covering solid rock. It includes dust, soil, broken rock, and other related materials and is present on Earth, the Moon, some asteroids, and other terrestrial planets and moons.-Etymology:...
, that would cut the construction costs of building on the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
.
Ingredients
Only comparatively small amounts of moon rock have been transported to Earth, so in 1988 researchers at the University of North DakotaUniversity of North Dakota
The University of North Dakota is a public university in Grand Forks, North Dakota, USA. Established by the Dakota Territorial Assembly in 1883, six years before the establishment of the state of North Dakota, UND is the oldest and largest university in the state and enrolls over 14,000 students. ...
proposed simulating the construction of such a material by using lignite coal ash. Other researchers have used the subsequently developed lunar regolith simulant
Lunar regolith simulant
A Lunar regolith simulant is a terrestrial material synthesized in order to approximate the chemical, mechanical, and engineering properties of, and the mineralogy and particle size distributions of, lunar regolith. Lunar regolith simulants are used by researchers who wish to research the...
materials, such as JSC-1 (developed in 1994 and as used by Toutanji et al.). Some small-scale testing, with actual regolith, has been performed in laboratories, however.
The basic ingredients for lunarcrete would be the same as those for Terrestrial concrete: aggregate, water, and cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
. In the case of lunarcrete, the aggregate would be lunar regolith. The cement would be manufactured by beneficiat
Beneficiation
In mining, beneficiation is a variety of processes whereby extracted ore from mining is separated into mineral and gangue, the former suitable for further processing or direct use....
ing lunar rock that had a high calcium content. Water would either be supplied from off the moon, or by combining oxygen with hydrogen produced from lunar soil
Lunar soil
Lunar soil is the fine fraction of the regolith found on the surface of the Moon. Its properties can differ significantly from those of terrestrial soil...
.
Lin et al. used 40g of the lunar regolith samples obtained by Apollo 16
Apollo 16
Young and Duke served as the backup crew for Apollo 13; Mattingly was slated to be the Apollo 13 command module pilot until being pulled from the mission due to his exposure to rubella through Duke.-Backup crew:...
to produce Lunarcrete in 1986. The Lunarcrete was cured by using steam on a dry aggregate/cement mixture. Lin proposed that the water for such steam could be produced by mixing hydrogen with lunar ilmenite
Ilmenite
Ilmenite is a weakly magnetic titanium-iron oxide mineral which is iron-black or steel-gray. It is a crystalline iron titanium oxide . It crystallizes in the trigonal system, and it has the same crystal structure as corundum and hematite....
at 800°C, to produce titanium oxide
Titanium oxide
Titanium oxide may refer to:* Titanium dioxide , TiO2* Titanium oxide , TiO, a non-stoichiometric oxide* Titanium oxide , Ti2O3* Ti3O* Ti2O* δ-TiOx...
, iron, and water. It was capable of withstanding compressive pressures of 75 MPa, and lost only 20% of that strength after repeated exposure to vacuum.
In 2008, Houssam Toutanji, of the University of Alabama in Huntsville
University of Alabama in Huntsville
The University of Alabama in Huntsville is a state-supported, public, coeducational research university, located in Huntsville, Alabama, United States, is accredited by the Southern Association of Colleges and Schools to award baccalaureate, master's and doctoral degrees, and is organized in five...
, and Richard Grugel, of the Marshall Space Flight Center
Marshall Space Flight Center
The George C. Marshall Space Flight Center is the U.S. government's civilian rocketry and spacecraft propulsion research center. The largest center of NASA, MSFC's first mission was developing the Saturn launch vehicles for the Apollo moon program...
, used a lunar soil simulant to determine whether Lunarcrete could be made without water, using sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
(obtainable from lunar dust) as the binding agent. The process to create this sulfur concrete
Sulfur concrete
Sulfur concrete is a composite construction material, composed of sulfur, aggregate ....
required heating the sulfur to 130–140°C. After exposure to 50 cycles of temperature changes, from -27°C to room temperature, the simulant Lunarcrete was found to be capable of withstanding compressive pressures of 17MPa, which Toutanji and Grugel believed could be raised to 20MPa if the material were reinforced with silica (also obtainable from lunar dust).
Casting and production
There would need to be significant infrastructure in place before industrial scale production of lunarcrete could be possible.The casting of lunarcrete would require a pressurized environment, because attempting to cast in a vacuum would simply result in the water, required for the chemical reaction that forms the curing process, evaporating, and the lunarcrete failing to harden. Two solutions to this problem have been proposed: premixing the aggregate and the cement and then using a steam injection process to add the water, or the use of a pressurized concrete fabrication plant that produces pre-cast concrete blocks.
Lunarcrete shares the same lack of tensile strength
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...
as terrestrial concrete. One suggested lunar equivalent tensioning material for creating pre-stressed concrete is lunar glass, also formed from regolith, much as fibreglass is already sometimes used as a terrestrial concrete reinforcement material. Another tensioning material, suggested by David Bennett, is Kevlar
Kevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
, imported from Earth (which would be cheaper, in terms of mass, to import from Earth than conventional steel).
Use
David Bennett, of the British Cement Association, argues that Lunarcrete has the following advantages as a construction material for lunar bases:- Lunarcrete production would require less energy than lunar production of steelSteelSteel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
, aluminiumAluminiumAluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
, or brickBrickA brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...
. - It is unaffected by temperature variations of +120°C to −150°C.
- It will absorb gamma rayGamma rayGamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s. - Material integrity is not affected by prolonged exposure to vacuum. Although free water will evaporate from the material, the water that is chemically bound as a result of the curing process will not.
He observes, however, that Lunarcrete is not an airtight material, and to make it airtight would require the application of an epoxy
Epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
coating to the interior of any Lunarcrete structure.
Bennett suggests that hypothetical lunar buildings made of Lunarcrete would most likely use a low-grade concrete block for interior compartments and rooms, and a high-grade Dense Silica Particle cement-based concrete for exterior skins.