MARTIAN
CEMENTS
Robert J. Milligan
4Frontiers
10th Annual International Mars Society Convention
August 30, 2007
1
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)
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
2
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”.
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
3
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).
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
4
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.
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
5

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

Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
6
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.

Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
7
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

Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
8
DISADVANTAGES OF MOS

Mixing the Oxide with the Epsomite



Stoichiometry is Critical for Good Concrete.


The hydroxide may drop out of solution before it
reacts with the epsomite.
Heat generated may lead to premature cure.
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.
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
9
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.
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
10
EARLY MARS
SO2
CO2
H2O, O2
Acid Rain
Steam
Basalt Flow
Martian Ocean
Dilute Aqueous H2SO4
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
11
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
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
12
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.
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
13
RESOLVING THE CHLORIDESULFATE 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

Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
14
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.
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
15
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

Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
16
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
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
17
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.
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
18
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
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
19
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.
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
20
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.
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
21
REFERENCES
Frank Crossman, et. al. , “A Study of Indus trial Processing a t the 4 Frontiers Gene ration II
Permanen t Mars Settleme nt”, Proc. 10 th Mars Soc. Conf. Aug 2007 .
R, Vernon K ramer, “Finding Useful Minerals and Mining on Mars Isn’t That Easy”,
Proc. Internationa l Space Deve lopment Conf . (2007)
M. A. Bu ll ock and J. M. Moore, “Atmosphe ric Conditions on Ea rly Mars and the
Mis sing Lay ered Ca rbona tes”,
www .lpi.usra.edu/m eetings/sul fates2006/pdf/7068.pdf
M. A. Shand, “The Ch emist ry and Techno logy of Magnes ia”, Wil ey, 2006
S. Kobaya shi, “Process for Reductive Calcining of Magnes ium Sulfate”, U.S. Patent
4,225,573 , 1979.
A. P. Koulohe ris, ed. “Evaluation of Potential Comm ercial Processes fo r the Production
of Sulf uric Acid from Phosphogyp sum”, Zellars-Willi ams , Inc., Prepared unde r contract
# 80-01-002 for Florida Instit ute of Phoph ate Research, Oct, 1981.
E. Gasafi, U. Jeske and T . Reinhard t, “Gipsreduk tion mit Kohlenstoff (Gyp sum
Reduc tion w it h Carbon)” , Karls ruh e Inves tigative Center Science Report FZKA 7189 ,
2006.
T. D. Whee lock and D. R. Boylan, “Reduc tive Decomposition of Calcium S ulfate”, US
patent 3,087,790 (to Iowa State Coll ege Research Founda tion) , April 30, 1963.
Robert J. Milligan
Aug. 2007
© 4Frontiers Corporation
22