Transcript Slide 1

New Cements Based on the Addition of Reactive
Magnesia to Portland Cement With or Without
Added Pozzolan.
Hobart, Tasmania, Australia
All I ask is that the industry think about what I am saying.
John Harrison B.Sc. B.Ec. FCPA.
www.tececo.com
1
Sustainability Issues
 Globally some 2 billion tonnes of cement, lime and
magnesia are produced annually consuming large
amounts of energy* and releasing chemically bound
CO2.
* Around 98% of the world’s energy is derived from fossil fuels that
when burnt to produce energy release vast amounts of CO2
– Responsible between 5% and 10% of global emissions
 The built environment is our footprint on earth.
– Buildings and infrastructure account for around 60% of the
anthropogenic materials flows on earth. Closing loops, reducing
emissions, lifetime and embodied energies and improving
durability will reduce the impact on earth systems.
Bats = Best Available Technologies
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2
Materials Science Issues
 Talked about
– Rheology
• Time for and method of placing and
finishing
– Shrinkage
• Cracking, crack control
– Durability and Performance
•
•
•
•
•
Sulphate and chloride resistance
Carbonation
Corrosion of steel and other reinforcing
Alkali aggregate reactions
Delayed ettringite formation
Should the
discussion be more
about how we could
fix the material,
overcoming rather
than tolerating and
mitigating these
problems?
 Rarely discussed
– Sustainability
• Emissions and embodied energies
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3
Conclusion
 Portlandite is the main problem with Portland
cement.
– Better to fundamentally fix the material than continue with what
amount to “band aid” fixes.
– The merits of removing and replacing Portlandite with another
less soluble, easily manufactured alkali should be considered.
 Technology improvements increase market share
and fuel economic growth
– Carbon trading and the BATS system will favour adoption of better
technologies.
The TecEco technology is an opportunity
to be taken not a threat to be ignored!
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4
TecEco Cement - Simple Yet Ingenious?
Glue as well as Velcro?
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.
Partially hydrated Portland cement paste [Soroos,1999 ].
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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5
TecEco Cements – A Blending System
Imagination is more
important than
knowledge,
knowledge is
limited.
Albert Einstein
TecEco cements are a system of blending reactive
magnesia, Portland cement and usually a pozzolan
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6
TecEco Cement Summary
 Two main formulation strategies so far:
– TecEco modified Portland cements.
• Contain more Portland cement than reactive magnesia
– Reactive magnesia hydrates in the same rate order as Portland cement
forming brucite which densifies, maintains pH and protects due to it’s low
solubility.
– Other benefits include improvements in rheology and possibly less
shrinkage
– TecEco eco-cements
• Contain more reactive magnesia than Portland cement
• Brucite in porous materials eventually carbonates
– Forming stronger fibrous minerals.
– Resulting in huge opportunities for abatement.
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7
Reactivity Overcomes Delayed Hydration.
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 about by cement chemists.
 The reactivity of magnesia is a function of the state of
disorder, specific surface area and glass forming impurities.
– The state of disorder is dependent on the temperature of calcining and
probably the most important, followed by the level of impurities such as
iron.
– Make a particle small enough and it will react with just about anything!
[1] Ramachandran V. S., Concrete Science, Heydon & Son Ltd. 1981, p 358-360.
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8
Replacing Portlandite with Brucite.
 Portlandite is reactive, carbonates readily and being
soluble can act as an electrolyte. TecEco remove
Portlandite in reactions with Pozzolans.
 TecEco replace Portlandite with brucite which is
much less reactive or soluble, does not act as an
electrolyte or carbonate as readily.
– Improving the rheology
– Using up bleed water as it hydrates
– Filling in the pores, increasing the density
– Sealing off the atmosphere
– Providing long term pH control
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The Results of Replacing Portlandite with Brucite.
 Greater Durability.
– TecEco cement concretes are not attacked by salts and do not carbonate as
readily.
 A Lower More Stable pH for much Longer? – Less Corrosion
– As Portlandite is removed the pH becomes governed by the solubility of brucite
and is much lower at around 10.5 -11 reducing problems such as AAR and
etching, but still high enough to keep Fe FeO and Fe3O4 stable (See Pourbaix
diagram).
 Increased Density
– Brucite also densifies the matrix by filling in pore spaces taking up mix and
bleed water as it hydrates reducing shrinkage. (brucite is 69 mass% water!)
 Improved Rheology
– Reactive magnesia being much finer acts as a lubricant for Portland cement:
– improving the rheology, reducing the water/cement ratio, improving strength
and reducing shrinkage.
 Greater Sustainability
– Superior durability and reabsorbtion of chemically released CO2
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10
Durability - Reduced Salt Attack and Carbonation
 Brucite has always played a protective role during salt attack.
Putting it in the matrix of concretes in the first place makes
sense.
 Brucite protects concrete from salts because of it’s low
solubility (reactivity, mobility)
– Ksp brucite = 1.8 X 10-11
5 orders of magnitude
-6
– Ksp Portlandite = 5.5 X 10
 Carbonation of brucite is slow
– Gor Brucite = -19.55
3 orders of magnitude
– Gor Portlandite = -64.62
 Carbonation of brucite is slightly expansive
– And results in surface tightening reducing further carbonation - not
cracking!
 Magnesite and hydromagnesite add strength
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11
A More Stable Long Term pH
Eh-pH or Pourbaix Diagram
The stability fields of iron in the
presence of oxygen and carbon
dioxide.
Source: Krauskopf K. B., Introduction to
Geochemistry, McGraw Hill Book Company,
1967, page 168, after Garrels & Christ (1965),
page 224.
As Portlandite is removed the pH
becomes governed by the solubility of
brucite and is much lower at around 10.5 11 reducing problems such as AAR and
etching, but still high enough to keep Fe
and Fe3O4 stable. The hydroxides of most
heavy metals are also least soluble at
around pH 10.5 - 11
TecEco
Cement
zone.
Fe2O3 is stable above around
pH 8.9. Fe2O3 does not
hydrate and protects steel.
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12
Reduced Steel Corrosion
 Brucite does not react
readily resulting in reduced
carbonation rates and
reactions with salts.
 Brucite is less soluble
resulting in less ionic
transport to complete a
circuit for electrolysis.
 Concrete with brucite is
denser (keeping water and
CO2 out.)
 Carbonation of brucite seals
the surface preventing
further carbonation.
Anode
Ionic transport
Cathode
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Increased Density
 Brucite extracts water,
expanding filling pores and
surrounding hydrated
cement grains. With initial
lower water cement ratios
this results in greater
density.
 Greater density results in
greater strength, more
durable concrete with a
higher salt resistance and
less corrosion of steel etc.
Picture Courtesy Applied Petrographic Services NSW Aust.
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TecEco Cements - Improved Rheology
 Suitable reactive magnesia is much finer than most other
cements such as Portland cement and carries what we
suspect is a high positive surface charge.
 Finely ground reactive magnesia therefore acts as a
plasticiser.
– Improving rheology
– Less water need be used resulting in greater strength and
reduced porosity.
– The proportion and cost of binders and plasticisers can be
reduced.
Tech Tendons
Second layer low slump TecEco
modified Portland cement concrete
First layer low slump TecEco
modified Portland cement concrete
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15
TecEco Cements – Improved Rheology (2)
Smaller grains (eg
microsilica) for even
better rheology.
Portland cement grains
Mean size 20 - 60
micron
Reactive Magnesia
grains Mean size 6 10 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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16
Dimensionally Neutral TecEco Modified
Portland Cement Concretes on Hydration?
 Portland cement shrinks around .05%. Over the long term much
more (>.1%).
 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[1]
<=116.96 % expansion depending on whether the water is coming from mix
water or bleed water from OPC.
• So far we have not observed shrinkage in TecEco modified Portland cement concretes
(10% subst, OPC) also containing flyash.
• Could it be that the water lost by Portland cement as it shrinks is used by the reactive
magnesia as it hydrates?
 At some ratio, thought to be around 10% reactive magnesia and
90% OPC volume changes cancel each other out and setting
and curing are close to neutral.
– More research is required for both modified Portland cements and eco-cements.
[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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17
No Volume Changes with TecEco Modified
Portland Cements on 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
– Surface shrinkage causing cracks to appear.
 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
– Slight expansion and densification of the surface preventing further
ingress of CO2 and carbonation.
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Potential for Neutral Cure Modified Portland Cement Concretes
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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19
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.
 TecEco cements are ideal for soil remediation and
immobilising/utilising toxic and hazardous wastes such
as fly and bottom ash, iron slags, red mud etc.:
– Brucite results in an ideal long term equilibrium pH of
10.5 – 11 at which most heavy metal hydroxides are
relatively insoluble.
– The OPC in TecEco cements takes up lead.
– TecEco cements are:
• Not attacked by ground or sea water salts.
• Thermodynamically more stable.
• May be dimensionally more stable.
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20
Summary of Ramifications of Adding Reactive Magnesia
 Durability: TecEco cements include highly insoluble minerals that last
indefinitely. They maintain pH at ideal levels, protecting steel reinforcing
and reducing alkali aggregate reactions.
 Easy to Use: With improved homogeneity and rheology. Fine magnesia
acts as a lubricant for Portland cement and takes up bleed water as it
hydrates.
 Greater Strength? Less shrinkage?: A lower water cement ratio could
mean greater strength and less shrinkage. Still to be examined but so far
so good!
 Waste Materials: TecEco cements and Eco-cements use a high
proportion of recycled materials.
 Insulating Properties / High Thermal Mass / Low Embodied Energy:
Eco-cement products will be favoured for energy conserving buildings.
 Recyclable: Eco-cement products can be reprocessed and reused,
making them more attractive to many users.
 A Fire Retardant: Brucite and magnesite are both fire retardants. TecEco
cement products put fires out by releasing CO2 at relatively low
temperatures
 Low Capital Cost: No new plant and equipment is required.
 Lower Materials Cost: With economies of scale TecEco cements should
be cheaper.
 Suitable for Immobilisation of Wastes and Environmentally Friendly!
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21
Basic Chemical Reactions
Notice the
low
solubility of
brucite
compared
to
Portlandite
and that
magnesite
is stronger
and adopts
a more
ideal habit
than calcite
& aragonite
In TecEco Modified Portland Cements
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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The Magnesium Thermodynamic Cycle
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Manufacture of Portland Cement
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24
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,.
– 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
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25
TecEco’s Immediate Focus
 Form strategic alliances with major companies.
 Raise money for Research – Around 4 millions 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 modified Portland
cements).
– 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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26
TecEco Minding the Future
 TecEco are aware of the enormous weight of
opinion necessary before standards can be
changed globally for TecEco modified 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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TecEco Cements - Sustainability
 In the take-make-waste linear system, which underpins the majority
of the world’s economies.
– Utility is added until final point of sale and from then on utility generally declines
until wastage it complete.
– If utility can be maintained by greater durability or reuse then the system must
produce less waste, slow down and consume less
 New materials are required that are more durable and that do not exit
the linear system forming return loops eliminating wastes, reducing
output and thus our take from natural ecosystems.
– TecEco cements have been designed with these desirable characteristics
 Energy costs money 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.
– Volume of built material has greater utility and is more validly compared.
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TecEco Eco - Cements for Sustainable Cities
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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
From
Manufacturi
ng Process
Energy
Release
100%
Efficient
(Mj.tonne-1)
Portlan
d
Cement
1807
CaCO3 +
Clay
1545.73
2828.69
CaCO3
1786.09
2679.14
MgCO3
1402.75
1753.44
MgO
2934.26
From
Manufacturin
g Process
Energy
Release with
Inefficiencies
(Mj.tonne-1)
3306.81
3667.82
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Relative to
Mineral
Resulting
in Cement
From
Manufacturi
ng Process
Energy
Release
100%
Efficient
(Mj.tonne-1)
From
Manufacturi
ng Process
Energy
Release
with
Inefficienci
es
(Mj.tonne-1)
Hydrated
OPC
1264.90
2314.77
Ca(OH)2
2413.20
3619.80
Mg(OH)2
2028.47
2535.59
30
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)
CaCO3
+ Clay
4188.93
7665.75
CaCO3
6286.62
8429.93
MgCO3
4278.39
5347.99
Relative
Product
Used in
Cement
From
Manufactur
ing
Process
Energy
Release
100%
Efficient
(Mj.metre-3)
From
Manufacturin
g Process
Energy
Release with
Inefficiencies
(Mj.metre-3)
Portland
Cement
5692.05
10416.45
MgO
9389.63
11734.04
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Relative to
Mineral
Resulting
in Cement
From
Manufactur
ing
Process
Energy
Release
100%
Efficient
(Mj.metre-3)
From
Manufacturing
Process
Energy
Release with
Inefficiencies
(Mj.metre-3)
Hydrated
OPC
3389.93
6203.58
Ca(OH)2
5381.44
8072.16
Mg(OH)2
4838.32
6085.41
31
Abatement of Emissions
 The production of Portland cement clinker, lime
and magnesia all consume energy
 Around 98% of the world’s energy is derived
from fossil fuels that when burnt to produce
energy release vast amounts of CO2
 The production of Portland cement, lime and
reactive magnesia also results in the release of
chemically bound CO2
 See newsletter 28 for more detail at
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But Maybe Less Energy!
 There are reasons however why given volume
production less energy should be required.
– The manufacture of magnesia is a benign process
occurring at relatively low temperatures and for which
waste energy should be able to effectively be used.
– The manufacture of more durable building materials
will mean that less energy is required per unit of time
because structures require replacing less often.
– The manufacture of reactive magnesia is suited to
new TecEco kiln technology in which 25% greater
efficiencies should result due to the capture of waste
heat from grinding.
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The Sustainability of TecEco Cements
 TecEco cements generally
– A high proportion of brucite compared to Portlandite is water and of
magnesite compared to calcite is CO2.
• Every mass unit of cement powder therefore produces a greater volume of
built environment than Portland other calcium based cements. Less need
therefore be used.
– Improved durability and other properties.
• Brucite is less soluble, mobile or reactive than Portlandite and not attacked
by salts.
• The Ph is lower but more stable resulting in less AAR, etching and other
problems but still high enough for longer, maintaining the passivity of steel
for longer.
– Improved durability will result in a lower use of materials and energy
over time saving money and the environment.
– A high proportion of pozzolanic or non reactive wastes can be included.
 TecEco eco-cements
– Carbon dioxide is also reabsorbed by brucite from the atmosphere.
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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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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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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
Emission/Sequestrati
on from Substituted
Eco-Cement (Tonne
for Tonne
Substitution
Assumed)
Net Abatement
If embodied energies are improved could
substitution mean greater market share?
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
Concretes already have low lifetime energies.
TOTAL
Figures are in millions of Tonnes
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Manufacture of Eco-Cement Products
Eco-Cement – One of Many
Possible Manufacturing Scenarios
Magnesite
Coal
Coal
Combustion
Bottom ash &
other wastes
as aggregates
Flyash
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
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CO2
Portland
Cement
Other ingredients
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TecEco Kiln Technology
 Remember:
The reactivity of most calcined materials including magnesia
is a function of the state of disorder, specific surface area
and glass forming impurities.
 What if calcining and grinding occurred at the
same time?
– Heat would literally be squashed into the material to be
calcined, reducing the risk of overburning.
– The clastic conditions should increase the state of disorder and
reduce the formation of glasses resulting in greater reactivity.
– CO2 could be captured at source.
– The heat lost through grinding could be used for calcining
resulting in around 25% greater efficiency.
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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
ASR
Rheology
Shrinkage
Placement , Finishing
 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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TecEco Movie Theatre
Discovery Channel Movie
on Eco-Cements
Shown courtesy Discovery Channel Canada
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