1 martian cements robert j. milligan 4frontiers 10th annual international mars society convention...

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MARTIAN CEMENTS

Robert J. Milligan

4Frontiers

10th Annual International Mars Society Convention

August 30, 2007

© 4Frontiers Corporation 2 Robert J. MilliganAug. 2007

PORTLAND CEMENT

Baseline for the World (Relatively) easy-to-get precursors on Earth

Limestone or Calcium Carbonate Sand or Silica Alumina Iron Oxide (Hematite) And finally a dash of Gypsum (Calcium Sulfate)


CHEMISTRY

The Limestone, Silica, Alumina and Iron Oxide are Pulverized and Mixed in a Rotary Kiln.

The temperature is increased to ~1480ºC. The calcium carbonate decomposes to form calcium oxide

(quicklime) and carbon dioxide (calcination). The calcium oxide reacts with the other oxides to form:

Dicalcium and tricalcium silicates, Tricalcium aluminate, Tetracalcium ferroaluminate.

This mass sinters together in what is called “clinker”.


FURTHER PROCESSING

The Clinker is Removed from the Rotary Kiln and Pulverized.

Roughly 5% by Weight Gypsum (Calcium Sulfate) is Added During the Pulverization for Esthetic Effects (It Lightens the Color and Helps Provide a Smooth Surface).


NOW LETS TAKE THIS TECHNOLOGY TO MARS Materials:

Limestone No Limestone Beds have been Found on Mars. Cement Plants are Operating in Europe in which Gypsum (Calcium

Sulfate) has been Substituted for Limestone. The Pyrolysis is Done in the Presence of a Reducing Agent

(Carbon Monoxide, Carbon Powder). The Sulfur Dioxide Expelled from the Reaction is Oxidized and

Hydrolyzed to Sulfuric Acid. Gypsum has been Identified on Mars.


Materials (cont.) Silica

Not Known in Any Sort of Concentration on Mars until this Spring.

Alumina Not Known in Concentration on Mars. Aluminum Ore Containing Silts (Muds) Have Been

Identified. May be Able to Tap The Modified Alkaline Bayer

Process for Silica and Alumina. Iron Oxide

Hematite is Available Jarosite, KFe3(SO4)2(OH)6 Is Also Known


MOS SOREL CEMENT

A Less Cumbersome Cement to Make on Mars is that Known as Magnesium Oxy-Sulfate (MOS) Sorel Cement.

Only One Material, MgSO4•H2O (Kieserite), needs to be Beneficiated.

Kieserite is Purified, Dehydrated and a Portion is Calcined to Form MgO (Magnesia). Reductive Calcination takes Place at a Lower Temperature than

That for Calcium Oxide Magnesia is also useful for the preparation of refractory brick

for steelmaking.


PREPARATION OF MOS CEMENT

An Aqueous Solution of Epsomite, MgSO4•7H2O is Prepared. The Solution is Generally Quite Concentrated With Epsomite

Solids Levels From 35 to 65%. Magnesium Oxide is Then Added to the Solution. Care is Taken

not to Overheat (Initiate Cure) and External Cooling is Often Used.

The Stoichiometry is 5 Moles of MgO for Every Mole of Epsomite.

The Final Cement has a Molecular Formula of: 5MgO•MgSO4•8H2O


DISADVANTAGES OF MOS

Mixing the Oxide with the Epsomite The hydroxide may drop out of solution before it reacts

with the epsomite. Heat generated may lead to premature cure.

Stoichiometry is Critical for Good Concrete. Improper Stoichiometry Causes Exfoiliation.

There is a Moisture Problem with the Material. This is Much Less of a Problem on Mars than it is on

Earth.


MARTIAN GEOLOGIC HISTORY

Early Mars had an Atmosphere and Oceans It Also had Volcanic Activity

Sulfur Dioxide (SO2) and Basaltic Lava

The SO2 Entered the Early Oceans to Form (in Combination with Oxygen from the Atmosphere) Sulfuric Acid.

The Basalt Formed the Major Part of the Beds of these Oceans and was Adding to these Beds During Periods of Volcanic Activity.


Acid Rain

SO2

Basalt FlowSteam

Martian Ocean

CO2

H2O, O2

Dilute Aqueous H2SO4

EARLY MARS


THE CIRCUMSTANTIAL EVIDENCE

The Presence of Sulfates Kieserite, MgSO4•H2O, Gypsum, CaSO4•2H2O,

Jarosite, KFe3(SO4)2(OH)6. The Type of Silica that Spirit Found.

Indicated Production at Low Temperature The Lack of Structured Deposits of Carbonates.

Oceans were Never Basic Enough to Dissolve Carbon Dioxide


CHEMICAL EVIDENCE

Dilute Hydrochloric Acid (HCl) Dissolves Olivine and Calcium-Rich Plagioclases Such as Anorthite. The Sodium-Rich Plagioclases Appear to be Unaffected.

Hot HCl attacks Iron-Rich Pyroxene. Magnesium Rich Pyroxene Appears to Remain Unaffected.

Basalt is Composed of These Three Minerals.


RESOLVING THE CHLORIDE-SULFATE DIFFERENCE Sulfate Ions are Larger than Chloride Ions

May React Slower with Ions in a Crystal Structure if at All

The Martian Oceans Most Likely had Chloride Ions in Solution as Well. The Chloride Ions Could Extract the Metal From the Crystalline

Structure, be Replaced by Sulfate and Extract Again (A Catalyst).

The Oceans had At Least 10E8 Martian Years to React with the Basalt in the Beds


FURTHER MARTIAN GEOLOGIC HISTORY Gradually Volcanism Ceased and the Planet Cooled. Mars Lost its Atmosphere Because of the Lower Mass of

the Planet and the Lack of a Magnetic Field. The Sulfate Ions were Eventually Used up and the Ph of

the Martian Oceans Increased. As the Oceans Were Not Being Replenished with Water,

They Began to Evaporate.


THE DEPOSITS Silica is Insoluble and Would have Deposited on the Bed. Gypsum is Soluble in Acid. Depending on the Ph of the Ocean

when Evaporated, the Gypsum Could be Found Either Deposited on the Bed (high Ph) or with Kieserite on the Surface (low Ph).

Iron and Aluminum Sulfates May be Found Together. Of the Metals Found in Basalt, Aluminum is the Only One So-Far not Identified With a Sulfate. These Deposits or Similar Ores Should be Below the

Exposed Kieserite Layer. The Colonists Would Use Hematite and Alumina from the

Alkaline Bayer Process for Portland Cement


BENEFACTION AND CALCINATION

The Gypsum Will Have to be Separated From Whatever Co-Crystallized with It. Solubility Differences

It is then Dehydrated and Calcined to the Oxide. This Reductive Calcination will be done Separately as CaO is

Needed for Other Operations. Source for Base Ca(OH)2 for Neutralization of Acid Solution in

Gypsum Purification. Base in Alkaline Bayer Extraction of Alumina from Plagioclase


SUMMARY

In Summary Despite the Fact that All of the Constituents of Portland Cement can be Arrived At, MOS Sorel Cement Appears to be the Material of Choice. Only one Material to Beneficiate. Reductive Pyrolysis can be Carried Out at a Lower

Temperature. No Subsequent Grinding Step, the Cement is Formed as

a Concentrated Aqueous Solution.


CONCRETE FROM PORTLAND CEMENT Portland Cement is Mixed with Sand, Gravel and Water

to Form Concrete. The Sand and Gravel is Prewashed to Ensure that no Soluble

Species that Could Detract from the Performance of the Concrete is Present in the Mixture.

Sand is Primarily Silica on Earth. There is no Silica Sand on Mars.

Portland Cement is a Hydraulic Cement Implying that the Cement Adds Water Chemically as it Reacts to Form Concrete. Generally recognized as hydration of calcium oxide


CONCRETE MANUFACTURE ON MARS Both Martian Temperature and Pressure Mitigate

Against Formation of Concrete From Portland Cement in the Open. Concrete Articles Can Be Built under Near Earthlike

Conditions, Cured and then Transported to Where They are Needed.

Limits the size and mass of what can be fabricated.


CONCRETE MANUFACTURE WITH MOS ON MARS The MOS Concrete Can be Poured on Site

Provided the Martian Temperature Initially is Low Enough to Not Allow the Water to Boil. The Freezing Point Depression of the Solution Should be

Low Enough to Allow this to Happen. MOS Concretes Can be Used as Grout to Bind Together

Pieces of Portland Concrete.


REFERENCESFrank Crossman, et. al., “A Study of Industrial Processing at the 4Frontiers Generation IIPermanent Mars Settlement”, Proc. 10th Mars Soc. Conf. Aug 2007.

R, Vernon Kramer, “Finding Useful Minerals and Mining on Mars Isn’t That Easy”,Proc. International Space Development Conf. (2007)

M. A. Bullock and J. M. Moore, “Atmospheric Conditions on Early Mars and theMissing Layered Carbonates”,www.lpi.usra.edu/meetings/sulfates2006/pdf/7068.pdf

M. A. Shand, “The Chemistry and Technology of Magnesia”, Wiley, 2006

S. Kobayashi, “Process for Reductive Calcining of Magnesium Sulfate”, U.S. Patent4,225,573, 1979.

A. P. Kouloheris, ed. “Evaluation of Potential Commercial Processes for the Productionof Sulfuric Acid from Phosphogypsum”, Zellars-Williams, Inc., Prepared under contract# 80-01-002 for Florida Institute of Phophate Research, Oct, 1981.

E. Gasafi, U. Jeske and T. Reinhardt, “Gipsreduktion mit Kohlenstoff (GypsumReduction with Carbon)”, Karlsruhe Investigative Center Science Report FZKA 7189,2006.

T. D. Wheelock and D. R. Boylan, “Reductive Decomposition of Calcium Sulfate”, USpatent 3,087,790 (to Iowa State College Research Foundation), April 30, 1963.

1 martian cements robert j. milligan 4frontiers 10th annual international mars society convention...

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