New Materials Based on the Addition of
Reactive Magnesia to Hydraulic Cements.
Hobart, Tasmania, Australia
All I ask is that the industry think about what I am saying.
John Harrison B.Sc. B.Ec. FCPA.
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1
Materials - the Key to Sustainability
The choice of materials controls emissions, lifetime and
embodied energies, maintenance of utility, recyclability and
the properties of wastes returned to the biosphere.
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2
The Construction Industry
 The built environment is our footprint on earth.
 TecEco estimate that building materials comprise some 70%
of materials flows.
 Calcined minerals and their derivatives are the main
materials used to construct the built environment.
– Globally around 2 billion tonnes of calcined minerals (cement,
lime and magnesia) are produced annually.
– Portland cement is made by calcining limestone with clay and
concrete made with it is the most widely used material on
Earth.
– Global Portland cement production is in the order of 1.7 billion
tonnes. The largest producers of Portland cement are China
at over 500 million tonnes followed by India at over 110 million
tonnes. Globally this amounts to over 6 cubic kilometres of
concrete per year.
Downloaded from www.dbce.csiro.au/indserv/brochures/embodied/embodied.htm (last accessed 07 March 2000)
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3
Embodied Energy of Building Materials
Concrete has a relatively
low embodied energy
Downloaded from www.dbce.csiro.au/indserv/brochures/embodied/embodied.htm (last accessed 07 March 2000)
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4
Embodied Energy in Buildings
But because so much is
used there is a huge
opportunity for
sustainability
Downloaded from www.dbce.csiro.au/indserv/brochures/embodied/embodied.htm (last accessed 07 March 2000)
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5
Sustainability = High Performance
 Sustainability is not just about reducing emissions.
 Other properties of concrete such as the amount of cement
required for a given strength, durability, embodied energy,
insulating capacity, weight etc. are also relevant.
 Concretes should not be thought of as just cement and
aggregate. They will become a composite material with a
range of tailored properties offering vastly improved overall
performance as well as meeting specific performance criteria
such as strength.
 As an ideal building material concrete should include other
properties not usually provided such as insulating capacity
and the ability to utilise wastes.
– All sorts of other materials such as industrial mineral wastes, sawdust,
wood fibres, waste plastics etc. could be added for the properties they
impart.
– More attention paid to the micro engineering of the material as well as
the chemistry would result in improved properties.
 Concretes can cost affectively be everything we would like
them to be!
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6
Emissions
 Calcined mineral materials and their derivatives used in
construction such as Portland cement, lime and magnesia are
made from carbonates.
 The process of calcination involves driving off chemically
bound CO2 with heat.
MCO3 →MO + CO2
∆
 Heating requires energy. 98% of the world’s energy is derived
from fossil fuels. Fuel oil, coal and natural gas are mainly
directly or indirectly burned to produce the energy required
for calcining of metal carbonates releasing CO2.
 Most of the embodied energy in the built environment is in
concrete.
 The production of cement for concretes accounts for around
10% of global anthropogenic CO2.
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7
Opportunities for Sustainability
 The CO2 released by chemical reaction from the
calcined materials in TecEco Eco-cement concretes
can be captured during manufacture and
reabsorbed on a widely distributed basis in ecocements.
 A system using TecEco Eco-Cements to construct
the built environment therefore offers enormous
opportunities for sequestration, particularly if
combined with mineral sequestration utilising
magnesium silicates in a combined process.
 Other TecEco cements are also much more
sustainable but for different reasons that include
durability and the use of less cement to make more
material.
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8
Issues with OPC Concrete
 Talked about
– Rheology
• Workability, time for and method of placing and finishing
– Shrinkage
• Cracking, crack control
– Durability and Performance
•
•
•
•
•
Permeability and Density
Sulphate and chloride resistance
Carbonation
Corrosion of steel and other reinforcing
Delayed reactions (eg alkali aggregate
and delayed ettringite)
– Bonding to brick and tiles
– Efflorescence
Should the
discussion be
more about
how we could
fix the material,
overcoming
rather than
tolerating and
mitigating
these
problems?
 Rarely discussed
– Sustainability issues
• Emissions and embodied energies
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9
Engineering Issues are Mineralogical Issues
 Problems with Portland cement concretes are usually resolved
by the “band aid” application of engineering fixes. They are
rarely discussed in terms of the mineralogy. e.g.
– Use of calcium nitrite, silanes, cathodic protection or stainless steel to
prevent corrosion.
– Use of coatings to prevent carbonation.
– Crack control joins to mitigate the affects of shrinkage cracking.
– Plasticisers to improve workability, glycols to improve finishing.
 Many of the problems with Portland cement are better fixed by
fundamentally fixing the mineralogy!
 The flaw in the mineralogy of Portland cement concretes is the
presence of Portlandite which is too soluble, mobile and
reactive.
 The TecEco technology is not a “band aid”, it is a fundamental
fix.
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10
TecEco Technology - Simple Yet Ingenious?
The TecEco technology demonstrates that magnesia,
provided it is reactive rather than “dead burned” (or high
density, periclase type), can be beneficially added to
cements in excess of the amount of 5 mass% generally
considered as the maximum allowable by standards
Reactive magnesia is essentially
amorphous magnesia produced at low
temperatures and finely ground.
The important thing in science is not so much to obtain new
facts as to discover new ways of thinking about them.
-- Sir William Bragg
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11
TecEco Concretes – A Blending System
SUSTAINABILITY
PORTLAND
POZZOLAN
Hydration of the
various
components of
Portland cement
for strength
DURABILITY
Reaction of alkali with
pozzolans (e.g. lime
with fly ash.) for
sustainability,
durability and strength
TECECO CEMENTS
MAGNESIA
Hydration of magnesia → brucite.
Carbonation of brucite →
hydromagnesite and magnesite
for plasticity, durability and
sustainability.
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STRENGTH
TecEco concretes are
a system of blending
reactive magnesia,
Portland cement and
usually a pozzolan with
other materials.
12
Reactivity Overcomes Delayed Hydration Problems.
 Delayed hydration leads to dimensional distress.
– Magnesium was banned in Portland cements because when it goes
through the high temperature process of making Portland cement it
becomes periclase. It is “dead burned”, hydrates slowly and causes
dimensional distress.
– Dead burned lime is much more expansive than dead burned
magnesia(1), a problem largely forgotten by cement chemists.
 TecEco have demonstrated that highly amorphous reactive
magnesia can beneficially be added to concrete formulations
– The reactivity of magnesia is a function of the state of disorder (lattice
energy), specific surface area and glass forming impurities.
• The state of order or disorder is expressed in lattice energy and is dependent
on the temperature of calcining.
• Specific surface area relates particle size. Make a particle small enough and
it will react with just about anything.
• Glass forming impurities are formed when reactive magnesia reacts at high
temperatures with impurities such as iron.
 A new TecEco kiln technology which combines calcining and
grinding should make it possible to calcine at lower temperatures
and produce more reactive magnesia with reduced problems due
to impurities as well as capture CO2.
–
(1) Ramachandran V. S., Concrete Science, Heydon & Son Ltd. 1981,
p 358-360.
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13
Why Replace Portlandite with Brucite?
 Portlandite (Ca(OH)2) is not a suitable concrete matrix mineral.
 Ca(OH)2 is reactive, carbonates readily and being soluble can act
as an electrolyte. TecEco remove Portlandite in reactions with
Pozzolans.
 Brucite is much less soluble, mobile or reactive, does not act as an
electrolyte or carbonate as readily.
 The addition of magnesia which hydrates forming brucite improves
the rheology, uses up bleed water as it hydrates, filling in the pores,
increasing the density, reducing permeability, reducing shrinkage
and providing long term pH control with many consequences
including greater durability.
 In porous eco-cements brucite carbonates forming stronger
minerals.
The consequences of removing Portlandite (lime) with the
pozzolanic reaction and filling the voids between hydrating cement
grains with brucite, an insoluble alkaline mineral, need to be
considered.
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14
Portlandite Compared to Brucite
Property
Portlandite (Lime)
Brucite
Density
2.23
2.9
Hardness
2.5 – 3
2.5 – 3
Solubility (cold)
1.85 g L-1 in H2O at 0 oC
0.009 g L-1 in H2O at 18
oC.
Solubility (hot)
.77 g L-1 in H2O at 100 oC .004 g L-1 H2O at 100 oC
Solubility (moles, cold)
0.000154321 M L-1
0.024969632 M L-1
Solubility (moles, hot)
0.000685871 M L-1
0.010392766 M L-1
Solubility Product (Ksp)
5.5 X 10-6
1.8 X 10-11
Reactivity
High
Low
Form
Massive, sometime
fibrous
Usually fibrous
Free Energy of
Formation of
Carbonate Gof
- 64.62 kJ.mol-1
- 19.55 kJ.mol-1
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15
TecEco Formulations
 Three main formulation strategies so far:
– Tec-cements (e.g. 10% MgO, 90% OPC.)
• Contain more Portland cement than reactive magnesia.
– Reactive magnesia hydrates in the same rate order as Portland cement forming Brucite
which uses up water reducing the voids:paste ratio, increasing density and possibly
raising the short term pH. Reactions with pozzolans are more affective. After all the
Portlandite has been consumed Brucite controls the long term pH which is lower and
due to it’s low solubility, mobility and reactivity results in greater durability .
– Other benefits include improvements in density, strength and rheology, reduced
permeability and shrinkage and the use of a wider range of aggregates without reaction
problems.
– Enviro-cements (e.g. 25-75% MgO, 25-75% OPC)
• In non porous concretes brucite does not carbonate readily.
– High proportions of magnesia are most suited to toxic and hazardous waste
immobilisation and when durability is required. Strength is not developed quickly.
– Eco-cements (egg 50-75% MgO, 50-25% OPC)
• Contain more reactive magnesia than in tec-cements.
• Brucite in porous materials carbonates
– Forming stronger fibrous mineral carbonates.
– Presenting huge opportunities for abatement.
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16
TecEco Formulations (2)
OPC
Tec-cement
Enviro-cement
Eco-cement
Fly ash & other
pozzolans
Magnesia
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17
Porosity and Magnesia Content
Note that TecEco eco-cements
require a porous environment.
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18
Basic Chemical Reactions
In TecEco Modified Portland Cements
Notice the
low
solubility of
brucite
compared
to
Portlandite
and that
magnesite
is stronger
and adopts
a more
ideal habit
than calcite
& aragonite
Magnesia
Brucite
MgO + H2O  Mg(OH)2
In Eco - Cements
Magnesia
Brucite
Silicates and aluminosilicates
Magnesite
Hydromagnesite
MgO + H2O  Mg(OH)2 + CO2  MgCO3 + Mg(OH)2.4MgO.4CO2.4H2O
Form: Massive-Sometimes Fibrous Often Fibrous Acicular - Needle-like crystals
Hardness:
2.5 - 3.0
Solubility (mol.L-1): .00015
4.0
3.5
.0013
.0011
Compare to Portlandite
Portlandite
Calcite
Aragonite
Ca(OH)2 + CO2  CaCO3
Form:
Massive
Hardness:
2.5-3.00
Solubility (mol.L-1): .024
Massive or crystalline
More acicular
3.0
.00014
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19
Greater Strength
 Tec-cements can be made with at least 25% less
binder for the same strength.
 Possible reasons for
– Low binder/total solids ratio
– More rapid strength development even with pozzolans
Concrete
technologists
are
obsessed by
strength.
They should
be more
interested in
durability!
• Reactive magnesia is an excellent plasticiser and results
in:
– Denser, less permeable concrete.
– A significantly lower voids/paste ratio.
• Higher early pH initiating more effective silicification
reactions
– The Ca(OH)2 normally lost in bleed water is used internally for
reaction with pozzolans.
– Super saturation caused by the removal of water by magnesia as it
hydrates.
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20
Rapid Water Reduction
Primary
Observation
Water
Consumption
of water during
plastic stage
Relevant
Fundamental
Voids
Paste
Paste
Binder++
Binder
suppleme
suppleme
ntary
ntary
cementiti
cementiti
ous
ous
materials
materials
High water
for ease of
placement
Variables such as %
hydration of mineral,
density, compaction,
% mineral H20 etc.
Log time
Less water
for strength
and durability
Less water results in less shrinkage and cracking and
improved durability. Concentration of alkalis and
increased density result in greater strength.
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Water is
required to
plasticise
concrete for
placement,
however once
placed, the less
water over the
amount
required for
hydration the
better.
Magnesia
rapidly removes
water as it
hydrates.
21
Durability & Strength - Increased Density
 Concretes have a high percentage of voids.
 On hydration magnesia expands 116.9 % filling voids
and surrounding hydrating cement grains.
 Brucite is 44.65 mass% water.
 Lower voids:paste ratios than water:binder ratios result
in less bleed water and greater density.
 Greater density results in greater strength, more
durable concrete with a higher salt resistance and less
corrosion of steel etc.
 Self compaction of brucite may add to strength.
– Compacted brucite is as strong as CSH (Ramachandran,
Concrete Science p 358)
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22
Hypothetical Tec-Cement pH Curves
pH
HYPOTHETICAL pH CURVES
OVER TIME
13.7
OPC Concrete
10.5
Plastic
Stage
Tec – Cement Concrete with 10%
reactive magnesia
Log Time
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23
Hypothetical Tec-Cement Concrete Strength Development Curve
HYPOTHETICAL STRENGTH
GAIN CURVE OVER TIME
(Pozzolans added)
Mpa
Tec – Cement Concrete with
10% reactive magnesia
?
?
?
OPC Concrete
?
7
Plastic
Stage
14
28
Log Days
The possibility of high early strength gain
with added pozzolans is of great economic
importance.
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24
Durability - A Lower More Stable Long Term pH
In TecEco cements the long
term pH is governed by the
low solubility and carbonation
rate of brucite and is much
lower at around 10.5 -11,
allowing a wider range of
aggregates to be used,
reducing problems such as
AAR and etching. The pH is
still high enough to keep
Fe2O3 and Fe3O4 stable in
reducing conditions.
Eh-pH or Pourbaix Diagram
The stability fields of hematite,
magnetite and siderite
in aqueous solution; total
dissolved carbonate = 10-2M.
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The Passive Coating of Iron Oxide
 The passive coating on steel is iron oxide. According to
the Pourbaix diagram it is magnesite but some authors
such as Neville report the oxide is γFe3O(1).
 One of the problems associated with examining iron
oxides is that they change rapidly from one form to
another and are therefore difficult to characterise(2).
 The author would be interested in definitive information
of any papers on this subject!
(1) Neville, A. M. Properties of Concrete, 4th Ed.
Pearson Prentice Hall, England, 2003, page 563.
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26
Durability – Reduced Delayed Reactions
A wide range of delayed reactions can
occur in Portland cement based concretes
– Delayed alkali silica and alkali carbonate
reactions
– The delayed formation of ettringite and
thaumasite
– Delayed hydration of minerals such as dead
burned lime and magnesia.
Delayed reactions cause dimensional
distress and possible failure.
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27
Durability – Reduced Delayed Reactions (2)
 Delayed reactions do no occur to the same
extent in TecEco Cements.
– A lower long term pH results in reduced reactivity
after the plastic stage.
– Potentially reactive ions are trapped in the
structure of brucite.
– Ordinary Portland cement concretes can take
years to dry out however Tec-cement concretes are
dried out from the inside by the water demand of
reactive magnesia as it hydrates.
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28
Durability – Carbonation
 Carbonates are the stable phases of both calcium and
magnesium.
 Carbonates lower the pH of concretes compromising
the stability of the passive oxide coating on steel.
 The Portlandite in Portland cement concretes
carbonates readily starting at the surface.
 Brucite in tec - cement concretes carbonates less
readily (for the main kinetic pathway) because:
– The carbonation reaction has a less negative Gibbs free
energy.
• Gor Brucite = -19.55
• Gor Portlandite = -64.62
– Carbon dioxide cannot enter the dense impermeable
concrete matrix.
– The magnesium carbonates that form at the surface of tec –
cement concretes expand, sealing off further carbonation.
 Eco-Cement Concretes
– Magnesite is formed deliberately and is stronger and more
acid resistant than calcite or aragonite.
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Durability – Reduced Permeability
 As bleed water exits ordinary
Portland cement concretes it
creates an interconnected pore
structure that remains in concrete
allowing the entry of aggressive
agents such as SO4--, Cl- and CO2
 TecEco tec - cement concretes are
a closed system. They do not bleed
as excess water is consumed by
the hydration of magnesia.
– As a result TecEco tec - cement concretes
dry from within, are denser and less
permeable, and cement powder is not lost
near the surfaces.
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30
Reduced Shrinkage
Portland Cement Concretes
Tec-Cement Concretes
Drying Shrinkage
Plastic Settlement
Stoichiometric (Chemical) Shrinkage
None
Log Time, days
Dimensional change such as shrinkage
results in cracking and reduced durability
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Reduced Cracking in TecEco Cement Concretes
Reduced in
TecEco teccements
because
they do not
shrink.
Cracking, the
symptomatic result of
shrinkage, is
undesirable for many
reasons, but mainly
because it allows
entry of gases and
ions reducing
durability. Cracking
can be avoided only if
the stress induced by
the free shrinkage
strain, reduced by
creep, is at all times
less than the tensile
strength of the
concrete.
After Richardson, Mark G. Fundamentals of Durable Reinforced Concrete Spon Press, 2002. page 212.
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32
Corrosion in Portland Cement Concretes
Both carbonation, which
renders the passive iron
oxide coating unstable or
chloride attack (various
theories) result in the
formation of reaction
products with a higher
electrode potential
resulting in anodes with
the remaining passivated
steel acting as a cathode.
Passive Coating Fe3O4 intact
Corrosion
Anode: Fe → Fe+++ 2eCathode: ½ O2 + H2O +2e- →
2(OH)Fe++ + 2(OH)- → Fe(OH)2 + O2 →
Fe2O3 and Fe2O3.H2O (iron oxide
and hydrated iron oxide or rust)
The role of chloride in Corrosion
Anode: Fe → Fe+++ 2eCathode: ½ O2 + H2O +2e- → 2(OH)Fe++ +2Cl- → FeCl2
FeCl2 + H2O + OH- → Fe(OH)2 + H+ + 2ClFe(OH)2 + O2 → Fe2O3 and Fe2O3.H2O
Iron hydroxides react with oxygen to form rust.
Note that the chloride is “recycled” in the reaction
and not used up.
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33
Reduced Steel Corrosion
 A pH of over 8.9 is maintained for much longer and steel
remains passive due to a stable oxide coating.
 Brucite does not react readily resulting in reduced
carbonation rates and reactions with salts.
 Concrete with brucite is denser and carbonation is
expansive, sealing the surface preventing further access
by moisture, CO2 and salts.
 Brucite is less soluble and traps salts as it forms resulting
in less ionic transport to complete a circuit for
electrolysis and less corrosion.
 Free chlorides and sulfates originally in cement and
aggregates bound by magnesium
– Magnesium oxychlorides or oxysulfates are formed. ( Compatible
phases in hydraulic binders that are stable provided the concrete
is dense and water kept out.)
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Durability - Reduced Salt Attack
 Brucite has always played a protective role
during salt attack. Putting it in the matrix of
concretes in the first place makes sense.
 Brucite does not react with salts because
of it’s low solubility (reactivity, mobility) and
lower pH (reactivity)
– Ksp brucite = 1.8 X 10-11
– Ksp Portlandite = 5.5 X 10-6
- 5 orders of magnitude
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35
Improved Workability
Finely ground reactive magnesia acts as a
plasticiser.
– Improving rheology
– Lower water cement ratio results in greater
strength and reduced porosity.
– The proportion and cost of binders and
plasticisers can be reduced.
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36
Reasons for Improved Workability
Smaller grains (eg
microsilica) for even
better rheology.
Portland cement grains
Mean size 20 - 40
micron
Reactive Magnesia
grains Mean size 5 8 micron
The magnesia
grains act as ball
bearings to the
Portland cement
grains and also fill
the voids densifying
the whole
There are also surface charge affects and
water reducing agents are not required.
Reactive Magnesia is a plasticiser as well.
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37
Rheology
Tech Tendons
Second layer low slump TecEco
modified Portland cement concrete
First layer low slump TecEco
modified Portland cement concrete
 TecEco concretes are
– very homogenous
– very thixotropic and react well to energy input.
• (Slump is therefore not a good measure of workability)
 TecEco concretes with the same water/binder ratio
have a lower slump but greater plasticity and
workability.
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Dimensionally Neutral TecEco Tec - Cement
Concretes During Curing?
 Portland cement shrinks around .05%. Over the long
term much more (>.1%).
– Mainly due to chemical shrinkage, plastic and drying shrinkage,
as well as carbonation.
 Hydration:
– When magnesia hydrates it expands:
MgO (s) + H2O (l) ↔ Mg(OH)2 (s)
40.31 + 18.0 ↔ 58.3 molar mass
11.2 + liquid ↔ 24.3 molar volumes
– Up to 116.96% solidus expansion depending on whether the water is
coming from stoichiometric mix water, bleed water or from outside the
system. In practice much less as the water comes from mix and bleed
water.
– So far we have not observed shrinkage in TecEco tec - cement
concretes (10% substitution OPC) also containing fly ash.
– The water lost by Portland cement as it shrinks is used by the reactive
magnesia as it hydrates eliminating shrinkage.
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39
Volume Changes on Carbonation
 Carbonation:
– Consider what happens when Portlandite carbonates:
Ca(OH)2 + CO2  CaCO3
74.08 + 44.01 ↔ 100 molar mass
33.22 + gas ↔ 28.10 molar volumes
• 18.22% shrinkage. Cracks appear allowing further carbonation.
– Compared to brucite forming magnesite as it carbonates:
Mg(OH)2 + CO2  MgCO3
58.31 + 44.01 ↔ 84.32 molar mass
24.29 + gas ↔ 28.10 molar volumes
• 15.68% expansion and densification of the surface preventing further
ingress of CO2 and carbonation. Self sealing?
 Combined - Curing and Carbonation are close to
Neutral.
– At some ratio, thought to be around 10% reactive magnesia and 90%
OPC volume changes cancel each other out.
– More research is required for both tec - cements and eco-cements to
accurately establish volume relationships.
[1] The molar volume (L.mol-1)is equal to the molar mass (g.mol-1) divided by the density
(g.L-1).
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Tec - Cement Concretes - Potential for Neutral Cure
Reactive Magnesia
?
+.05%
+- Fly Ash?
?
?
?
?
Composite Curve
?
?
28
?
90 days
-.05%
Portland Cement
HYDRATION THEN CARBONATION OF REACTIVE MAGNESIA AND OPC
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Are the Texts all Wrong About Carbonation?
 Most texts maintain the carbonation reaction is one
between ions in solution yet carbonation is observable in
very dry conditions. The transport of carbon dioxide is
much more rapid in air than in water and adherence to Le
Chatelier’s principal would also indicate dry conditions as
the removal or water as a product would help the reaction
Ca(OH)2 + CO2  CaCO3 + H2O (Gof - 64.62 kJ.mol-1)
To proceed towards products (the right).
 The highly negative Gibbs free energy of the reaction
indicates this should occur spontaneously.
 The author would be very interested in some definitive
information on this as most of the texts seem to take a bet
both ways!
Please contact me if you know
more about this than me!
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42
Safety – Reduced Fire Damage
 The main phase in TecEco tec - cement concretes is brucite.
 The main phases in TecEco eco-cements are magnesite and
hydromagnesite.
 Brucite, magnesite and hydromagnesite are excellent fire
retardants and extinguishers.
 At relatively low temperatures
– Brucite releases water and reverts to magnesium oxide.
– Magnesite releases CO2 and converts to magnesium oxide.
– Hydromagnesite releases CO2 and water and converts to magnesium
oxide.
 Fires are therefore not nearly as aggressive resulting in less
damage to structures.
 Damage to structures results in more human losses that direct
fire hazards.
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TecEco Eco-Cements - Solving Waste Problems
 The best thing to do with wastes is if at all possible
to use them. If they cannot directly be used
then they have to be immobilised.
 Concretes represent a cost affective option:
 Chemically and physically enviro-cements are more
suited to toxic and hazardous waste immobilisation
than either lime, Portland cement or Portland cement
lime mixes and they are more predicable than geopolymers.
 In a Portland cement brucite matrix
– OPC takes up lead, some zinc and germanium
– Brucite and hydrotalcite are both excellent hosts for toxic and hazardous
wastes. Brucite has a layered structure and traps neutral compounds
between the layers.
– Heavy metals not taken up in the structure of Portland cement minerals or
trapped within the brucite layers end up as hydroxides.
 The pH which is controlled in the long term by brucite is around
10.52, and is an ideal long term value at which most heavy metal
hydroxides are relatively insoluble.
 TecEco cements are also more durable, dense, impermeable and
homogenous. They do not bleed water, are not attacked by salts in
ground or sea water and dimensionally more stable with less
cracking.
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44
Toxic and Hazardous Waste Immobilisation
Layers of
electronically
neutral brucite
suitable for
trapping
balanced
cations and
anions as well
as other
substances
Brucite is an ideal mineral for trapping
toxic and hazardous wastes.
Salts and
other toxic
and
hazardous
substances
between
layers
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The brucite in TecEco
cements has a
structure comprising
electronically neutral
layers and is able to
accommodate a wide
variety of extraneous
substances between
the layers and cations
of similar size
substituting for
magnesium within the
layers and is known to
be very suitable for
toxic and hazardous
waste immobilisation.
45
Concentration of Dissolved Metal, (mg/L)
Lower Solubility of Metal Hydroxides
10
Pb(OH)2
2
10 0
10 -2
Cr(OH)3
Zn(OH)2
Ag(OH)
Cu(OH)2
Ni(OH)2
Cd(OH)2
Equilibrium pH of brucite
is 10.52 (more ideal)*
10 -4
*Equilibrium
pH’s in pure
water, no
other ions
present. The
solubility of
toxic metal
hydroxides is
generally less
at around pH
10.52 than at
higher pH’s.
10 -6
6
7
8
9
10
11
12
13
14
Equilibrium pH of
Portlandite is 12.35*
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46
High Performance = Sustainability=Lower Cost
 High Performance = Sustainability=Lower Cost
 Comprehensive high performance will include
improvements in:
– Compressive and tensile strength/binder ratios
– Durability, insulating capacity, ability to host wastes
– Weight etc. etc.
 Increased durability will result in lower
costs/energies/emissions due to less frequent
replacement.
 Improvements in insulating capacity will mean
lower lifetime as well as embodied energies in
buildings.
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47
TecEco Concretes - Lower Construction Costs
 Lower water binder ratio means less binders (eg
OPC) for same strength.
 Faster strength gain even with added pozzolans.
 Cheaper binders as less energy required and a
higher proportion is water.
 Elimination of shrinkage reducing associated costs.
 Elimination of bleed water enables finishing of lower
floors whilst upper floors still being poured.
 A high proportion of brucite compared to
Portlandite is water and of magnesite compared to
calcite is CO2.
– Every mass unit of TecEco cements therefore produces a
greater volume of built environment than Portland and other
calcium based cements. Less need therefore be used
reducing costs/energy/emissions.
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48
TecEco Concretes - Lower Construction Costs (2)
 Homogenous, so no under plastic necessary.
 Because reactive magnesia is also an excellent
plasticiser, other costly additives are not required
for this purpose.
 Easier placement and better finishing.
 A wider range of aggregates can be utilised
without problems reducing transport and other
costs/energies/emissions.
 Greater durability reduces costs over time.
 Reduced or eliminated carbon taxes.
 Eco-cements can to a certain extent be recycled.
 TecEco cements utilise wastes many of which
improve properties.
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49
Characteristics of TecEco Cements (1)
Portland
Cement
Concretes
Tec-Cement
Concretes
Enviro-Cement
Concretes
Eco-Cements
Typical
Formulations
100 mass% PC
8 mass% OPC, 72
mass % PC, 20
mass% pozzolan
20 mass% OPC, 60
mass % PC, 20
mass% pozzolan
50 mass% OPC,
30 mass % PC, 20
mass% pozzolan
Setting
Main strength
from hydration of
calcium silicates.
Main strength is
from hydration of
calcium silicates.
Magnesia hydrates
forming brucite
which has a
protective role.
Magnesia hydrates
forming brucite
which protects and
hosts wastes.
Carbonation is not
encouraged.
Magnesia
hydrates forming
brucite then
carbonates
forming magnesite
and
hydromagnesite.
Suitability
Diverse
Diverse. Ready mix
concrete with high
durability
Toxic and
hazardous waste
immobilisation
Brick, block,
pavers, mortars
and renders.
Mineral
Assemblage
(in cement)
Tricalcium
silicate, di
calcium silicate,
tricalcium
aluminate and
tetracalcium
alumino ferrite.
Tricalcium silicate, di calcium silicate, tricalcium aluminate,
tetracalcium alumino ferrite, reactive magnesia.
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50
Characteristics of TecEco Cements (2)
Portland Cement
Concretes
Tec-Cement
Concretes
Enviro-Cement
Concretes
Final
mineral
Assembla
ge (in
concrete)
Complex but
including tricalcium
silicate hydrate, di
calcium silicate
hydrate, ettringite,
monosulfoaluminat
e, (tetracalcium
alumino sulphate),
tricalcium alumino
ferrite hydrate,
calcium hydroxide
and calcium
carbonate .
Complex but including tricalcium silicate hydrate, di calcium
silicate hydrate, ettringite, monosulfoaluminate, (tetracalcium
alumino sulphate), tricalcium alumino ferrite hydrate, calcium
hydroxide, calcium carbonate, magnesium hydroxide and
magnesium carbonates.
Strength
(S19-21)
Variable. Mainly
dependent on the
water binder ratio
and cement
content.
Variable. Mainly
dependent on the
water binder ratio
and cement content.
Usually less total
binder for the same
strength
development
Variable, usually
lower strength
because of high
proportion of
magnesia in mix.
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Eco-Cements
Variable.
51
Characteristics of TecEco Cements (3)
Portland Cement
Concretes
Tec-Cement
Concretes
Enviro-Cement
Concretes
Eco-Cements
Rate of
Strength
Developm
ent (S28)
Variable. Addition
of fly ash can
reduce rate of
strength
development.
Variable. Addition of
fly ash does not
reduce rate of strength
development.
Slow, due to huge
proportion of
magnesia
Variable, but
usually slower as
strength develops
during carbonation
process.
pH
(S20,21)
Controlled by Na+
and K+ alkalis and
Ca(OH)2 in the
short term. In the
longer term pH
drops near the
surface due to
carbonation
(formation of
CaCO3)
Controlled by Na+ and K+ alkalis and
Ca(OH)2 and high in the short term. Lower in
the longer term and controlled by Mg(OH)2
and near the surface MgCO3
High in the short
term and
controlled by
Ca(OH)2. Lower in
the longer term
and controlled by
MgCO3
Rheology
(S32-35)
Plasticisers are
required to make
mixes workable.
Plasticisers are not necessary. Formulations
are generally much more thixotropic.
Plasticisers are not
necessary.
Formulations are
generally much
more thixotropic
and easier to use
for block making.
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52
Characteristics of TecEco Cements (4)
Portland Cement
Concretes
Tec-Cement
Concretes
Enviro-Cement
Concretes
Durability(
S22-25)
Lack of durability is
an issue with
Portland cement
concretes
Protected by brucite, are not attacked by
salts, do not carbonate, are denser and less
permeable and will last indefinitely.
Density
(S25)
Density is reduced
by bleeding and
evaporation of
water.
Do not bleed - water is used up internally resulting in greater
density
Permeabilit
y(S28)
Permeable pore
structures are
introduced by
bleeding and
evaporation of
water.
Do not bleed - water is used up internally resulting in greater
density and no interconnecting pore structures
Shrinkage
(S36-39)
Shrink around .05 .15 %
With appropriate blending can be made dimensionally neutral as
internal consumption of water reduces shrinkage through loss of
water and magnesium minerals are expansive.
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Eco-Cements
Protected by
brucite, are not
attacked by salts,
do not carbonate,
are denser and will
last indefinitely.
53
Characteristics of TecEco Cements (5)
Portland Cement
Concretes
Tec-Cement
Concretes
Enviro-Cement
Concretes
Insulating
Properties
Relatively low with
high thermal
conductivity around
1.44 W/mK
Depends on formulation but better
insulation as brucite is a better insulator
Thermal
Mass
High. Specific heat
is .84 kJ/kgK
Depends on
formulation but
remains high
Depends on formulation but remains high
Embodied
Energy (of
concrete)
Low, 20 mpa 2.7
Gj.t-1, 30 mpa 3.9
Gj.t-1 (1)
Approx 15-30%
lower due to less
cement for same
strength, lower
process energy for
making magnesia
and high pozzolan
content(2).
Lower depending
on formulation(2).
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Eco-Cements
Depends on
formulation but
better insulation as
brucite is a better
insulator and
usually contains
other insulating
materials
Depends on
formulation Even
lower due to lower
process energy for
making magnesia
and high pozzolan
content(2).
54
Characteristics of TecEco Cements (6)
Portland Cement
Concretes
Tec-Cement
Concretes
Enviro-Cement
Concretes
Eco-Cements
Recyclability
Concrete can only
be crushed and
recycled as
aggregate.
Can be crushed
and recycled as
aggregate.
Can be crushed and
fines re-calcined to
produce more
magnesia or
crushed and
recycled as
aggregate or both.
Can be crushed
and fines recalcined to
produce more
magnesia or
crushed and
recycled as
aggregate or both.
Fire
Retardant
Ca(OH)2 and
CaCO3 break down
at relatively high
temperatures and
cannot act as fire
retardants
Mg(OH)2 is a fire retardant and releases
H2O at relatively low temperatures.
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Mg(OH)2 and
MgCO3 are both
fire retardants and
release H2O or
CO2 at relatively
low temperatures.
55
Characteristics of TecEco Cements (7)
Portland Cement
Concretes
Tec-Cement
Concretes
Enviro-Cement
Concretes
Eco-Cements
Sustainability
A relatively low
embodied energy
and emissions
relative to other
building products.
High volume results
in significant
emissions.
Less binder for the
same strength and a
high proportion of
supplementary
cementitous
materials such as fly
ash and gbfs. Can
be formulated with
more sustainable
hydraulic cements
such as high belite
sulphoaluminate
cements. A wider
range of aggregates
can be used.
Greater durability.
A high proportion of
supplementary
cementitous
materials such as fly
ash and gbfs. Can
be formulated with
more sustainable
hydraulic cements
such as high belite
sulphoaluminate
cements. A wider
range of aggregates
can be used. Greater
durability.
A high proportion of
supplementary
cementitous
materials such as fly
ash and gbfs.
Carbonate in porous
materials
reabsorbing
chemically released
CO2
A wider range of
aggregates can be
used. Greater
durability.
Carbon
emissions
With 15 mass% PC
in concrete .32 t.t-1
After carbonation
approximately .299
t.t-1
With 15 mass% PC in concrete approx.29
t.t-1 After carbonation approximately .26 t.t-1
Could be lower using supplementary
cementitous materials and formulated with
other low carbon cement blends.
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With 11.25 mass %
magnesia and 3.75
mass % PC in
concrete .241 t.t-1
With capture CO2
and fly ash as low
as .113 t.t-1
56
TecEco Challenging the World
 Although the technology is new and not yet fully
characterised, TecEco challenge universities
governments and construction authorities to come to
grips with the new cement technology and quantify
performance in comparison to ordinary Portland cement
and other competing materials.
 At TecEco will do our best to assist.
 Negotiations are underway in many countries to organise
supplies to allow such scientific endeavour to proceed.
 The invention of the new TecEco cement system is an
enormous opportunity for the world to take materials
science, which is the key to sustainability, more
seriously.
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57
Addressing Issues in Concrete Science
 Addressing the research objectives of concrete science.
– Durability salt resistance and steel corrosion may become problems
of the past.
• Lower use of materials and energy
over time saving money and the environment.
– Lower more stable long term alkalinity.
• Reduced AAR and steel corrosion etc.
– Better rheology.
• Lower water cement ratio, less shrinkage, and easier placement.
– Other improved properties:
• Greater density, adjustable placing and finishing times. Fire retarding
properties
– Lower Costs
• Making reactive magnesia is a benign process with potential for using
waste energy and capture of CO2.
• A wider range of aggregates including wastes will be available
reducing cartage costs and emissions.
• Water or CO2 from the air comprise a high mass % and volume % of
the magnesium minerals in TecEco cements. Water and CO2 are free or
attract carbon credits
• Expensive plasticisers are not required
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58
TecEco’s Immediate Focus
 Form strategic alliances with major companies.
 Raise money for Research – Around 1 million dollars worth in
the pipeline.
 Concentrate on defined markets for low technical risk products
that require minimal research and development and for which
performance based standards apply.
– Carbonated products such as bricks, blocks, stabilised earth blocks,
pavers, roof tiles pavement and mortars that utilise large quantities of
waste and products where sustainability, rheology or fire retardation
are an issue. (Mainly eco-cement technology using fly ash).
– The immobilisation of wastes including toxic hazardous and other
wastes because of the superior performance of the technology and
the rapid growth of markets. (Eco-cements and tec - cements).
– Products such as oil renders and mortars where excellent rheology
and bond strength are required.
– Products where extreme durability is required.
– Products for which weight is an issue.
 Continue our awareness campaign regarding TecEco cements,
the new TecEco kiln design and the Tech Tendon method of
prestressing, partial prestressing and reinforcing.
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59
TecEco Minding the Future
 TecEco are aware of the enormous weight of
opinion necessary before standards can be
changed globally for TecEco tec - cement
concretes for general use.
– TecEco already have a number of institutions and universities
around the world doing research.
 TecEco have received huge global publicity – not all of
which is correct and have therefore publicly released the
technology.
– TecEco research documents are available from TecEco by request.
Soon they will be able to be purchased from the web site.
– Other documents by other researchers will be made available in a
similar manner as they become available.
Technology standing on its own is not inherently good. It still
matters whether it is operating from the right value system and
whether it is properly available to all people.
-- William Jefferson Clinton
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60
TecEco Technology Summary
 Simple, smart and sustainable?
– TecEco cement technology has resulted in potential solutions to a
number of problems with Portland and other cements including
durability and corrosion, the alkali aggregate reaction problem and
the immobilisation of many problem wastes and will provides a
range of more sustainable building materials.
Climate Change
Pollution
Durability
Corrosion
Strength
Delayed Reactions
Placement , Finishing
Rheology
Shrinkage
Carbon Taxes
 The right technology at the right time?
– TecEco cement technology addresses important triple bottom line
issues solving major global problems with positive economic and
social outcomes.
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61
The Magnesium Thermodynamic Cycle
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62
Manufacture of Portland Cement
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63
TecEco Eco - Cements for Sustainable Cities
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64
Manufacture of TecEco-Cements
Eco-Cement – One of Many
Possible Manufacturing Scenarios
Magnesite
Coal
Coal
Combustion
Flyash
Bottom ash &
other wastes
as aggregates
Caustic
Magnesia
Calcined
using waste
heat and/or
sustainable
energy
TecEco - Cements
Hydration using flue
cooling &/or
scrubbing water &
flue steam.
Carbonation using
warm CO2 rich
gases
EcoMasonry
Products
e.g. Bricks
& blocks
www.tececo.com
CO2
Portland
Cement
Other ingredients
65
Embodied Energy and Emissions
 Energy costs money and results in emissions and is the largest
cost factor in the production of mineral binders.
– Whether more or less energy is required for the manufacture of reactive
magnesia compared to Portland cement or lime depends on the stage in
the utility adding process it is measured.
– Utility is greatest in the finished product which is concrete. The volume
of built material is more relevant than the mass and is therefore more
validly compared. On this basis the technology is far more sustainable
than either the production of lime or Portland cement.
– The new TecEco kiln technology will result in around 25% less energy
being required and the capture of CO2 during production resulting in
lower costs and carbon credits.
 The manufacture of reactive magnesia is a benign process
that can be achieved with waste or intermittently available
energy.
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66
Energy – On a Mass Basis
Relative to
Raw Material
Used to
make
Cement
From
Manufactur
ing
Process
Energy
Release
100%
Efficient
(Mj.tonne-1)
From
Manufacturin
g Process
Energy
Release with
Inefficiencie
s (Mj.tonne-1)
Relative
Product
Used in
Cement
Portlan
d
Cement
CaCO3 +
Clay
1545.73
2828.69
CaCO3
1786.09
2679.14
MgCO3
1402.75
1753.44
MgO
From
Manufacturi
ng Process
Energy
Release
100%
Efficient
(Mj.tonne-1)
1807
2934.26
From
Manufacturi
ng Process
Energy
Release
with
Inefficienci
es
(Mj.tonne-1)
From
Manufacturin
g Process
Energy
Release with
Inefficiencies
(Mj.tonne-1)
Relative to
Mineral
Resulting
in Cement
From
Manufacturi
ng Process
Energy
Release
100%
Efficient
(Mj.tonne-1)
3306.81
Hydrated
OPC
1264.90
2314.77
Ca(OH)2
2413.20
3619.80
Mg(OH)2
2028.47
2535.59
3667.82
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67
Energy – On a Volume Basis
Relative
to Raw
Material
Used to
make
Cement
From
Manufacturi
ng Process
Energy
Release
100%
Efficient
(Mj.metre-3)
From
Manufacturin
g Process
Energy
Release with
Inefficiencies
(Mj.metre-3)
Relative
Product
Used in
Cement
Portland
Cement
CaCO3
+ Clay
4188.93
7665.75
CaCO3
6286.62
8429.93
MgCO3
4278.39
5347.99
MgO
From
Manufactur
ing
Process
Energy
Release
100%
Efficient
(Mj.metre-3)
5692.05
9389.63
From
Manufacturin
g Process
Energy
Release with
Inefficiencies
(Mj.metre-3)
Relative to
Mineral
Resulting
in Cement
From
Manufactur
ing
Process
Energy
Release
100%
Efficient
(Mj.metre-3)
10416.45
Hydrated
OPC
3389.93
6203.58
Ca(OH)2
5381.44
8072.16
Mg(OH)2
4838.32
6085.41
11734.04
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From
Manufacturing
Process
Energy
Release with
Inefficiencies
(Mj.metre-3)
68
CO2 Abatement –TecEco Eco-Cements
Eco-cements in
porous products
absorb carbon
dioxide from the
atmosphere.
Brucite
carbonates
forming
hydromagnesite
and magnesite,
completing the
thermodynamic
cycle.
On the basis of the volume of building materials
produced the figures are even better!
Portland
Cements
15 mass% Portland
cement, 85 mass%
aggregate
Emissions
.32 tonnes to the
tonne. After
carbonation.
Approximately .299
tonne to the tonne.
85 wt%
Aggregates
15 wt%
Cement
No Capture
Capture CO2
11.25% mass%
reactive magnesia,
3.75 mass%
Portland cement, 85
mass% aggregate.
11.25% mass%
reactive magnesia,
3.75 mass% Portland
cement, 85 mass%
aggregate.
Emissions
Emissions
.37 tonnes to the
tonne. After
carbonation.
approximately .241
tonne to the tonne.
.25 tonnes to the
tonne. After
carbonation.
approximately .140
tonne to the tonne.
Capture CO2.
Fly and Bottom
Ash
11.25% mass% reactive
magnesia, 3.75 mass%
Portland cement, 85
mass% aggregate.
Emissions
.126 tonnes to the tonne.
After carbonation.
Approximately .113 tonne
to the tonne.
Greater Sustainability
.299 > .241 >.140 >.113
Bricks, blocks, pavers, mortars and pavement made using ecocement, fly and bottom ash (with capture of CO2 during
manufacture of reactive magnesia) have 2.65 times less emissions
than if they were made with Portland cement.
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69
Global Abatement
Without CO2
Capture during
manufacture
(billion tonnes)
With CO2
Capture during
manufacture
(billion tonnes)
Total Portland Cement Produced Globally
1.80
1.80
Global mass of Concrete (assuming a
proportion of 15 mass% cement)
12.00
12.00
Global CO2 Emissions from Portland Cement
3.60
3.60
Mass of Eco-Cement assuming an 80%
Substitution in global concrete use
9.60
9.60
Resulting Abatement of Portland Cement CO2
Emissions
2.88
2.88
CO2 Emissions released by Eco-Cement
2.59
1.34
Resulting Abatement of CO2 emissions by
Substituting Eco-Cement
0.29
1.53
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70
Abatement from Substitution
Building
Material to be
substituted
Realisti
c%
Substitution
by
TecEco
technol
ogy
Size of
World
Market
(millio
n
tonnes
Substit
uted
Mass
(million
tonnes)
CO2
Fact
ors
(1)
Emission
From
Material
Before
Substituti
on
Concretes already have low lifetime energies.
If embodied energies are improved could
substitution mean greater market share?
Emission/Sequestrati
on from Substituted
Eco-Cement (Tonne
for Tonne
Substitution
Assumed)
Net Abatement
Emission
s - No
Capture
Emission
s - CO2
Capture
Abatem
ent - No
Capture
Abatem
ent
CO2
Capture
Bricks
85%
250
212.5
0.28
59.5
57.2
29.7
2.3
29.8
Steel
25%
840
210
2.38
499.8
56.6
29.4
443.2
470.4
Aluminium
20%
20.5
4.1
18.0
73.8
1.1
0.6
72.7
73.2
426.6
20.7
633.1
114.9
59.7
518.2
573.4
TOTAL
Figures are in millions of Tonnes
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71
Tripling Mineral Sequestration
As a method of capturing CO2 the kinetics of the following
reactions are being examined:
½Mg2SiO4 + CO2 → MgCO3 + ½SiO2 + 95kJ/mole
1/
2/ SiO + 2/ H O +
Mg
Si
O
(OH)
+
CO
→
MgCO
+
3
3 2 5
4
2
3
3
2
3 2
64kJ/mole
Of the above the second reaction with chrysotile or
serpentine as it is sometimes called is favoured as the
mineral is abundant.
At low partial pressures of CO2 and relatively low
temperatures, MgCO3 will break down yielding MgO and
CO2.
MgCO3 →MgO + CO2
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72
Tripling Mineral Sequestration (2)
Utilising a closed system such as
with TecEco Kiln technology the CO2
re-emitted can be captured for
industrial use (replacing alternative
production) or direct sequestration.
If the MgO is then used to make ecocement products the total CO2
captured is three moles to the mole
of serpentinite mined.
MgO +H2O → Mg(OH)2
Mg(OH)2 +CO2 → MgCO3 + H2O
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73
Tripling Mineral Sequestration (3)
 One tonne of chrysotile will sequester .588 tonnes CO2
producing 1.263 tonnes of magnesite.
 1.263 tonnes of magnesite will yield .538 tonnes of
reactive magnesia.
 .588 tonnes CO2 driven off by the low temperature
calcination of magnesia can be captured.
 The magnesia when it carbonates (directly or via the
hydroxide) will yield 1.263 tonnes of magnesite again
absorbing a further .588 tonnes of CO2
 A total of 1.176 tonnes of CO2 can therefore be directly
sequestered and a further .588 tonnes captured.
 Captured CO2 can be used to replace commercially
produced CO2 or sequestered by other means.
 Total sequestration possible is therefore three times
that possible with direct mineral sequestration alone!
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