An Overview of Future Concretes with a
Description of the Role of Reactive Magnesia
•Part 1
•Concrete – Where are we?
•Drivers for Change => Opportunities
•Barriers to Change
•Guides to Change
•Contenders with Commentary
•Part 2
•The Role of Reactive MgO
1
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Concrete - Where are we?
• The hard mineral composite we build with.
• Next to water the most used.
– Buildings account for ~40% of the materials and ~33% of the energy consumed by
the world economy. 1
– 7 billion M3 per annum 2
– 5% - 10% of CO2 emissions depending on the authority.
• Concrete infrastructure expenditure a huge investment for governments at all
levels
• A cost cutting volume business model for many players in the supply chain
• Already one of the most environmentally friendly building materials –
significant improvements are possible however.
• Affect on embodied energies and emissions as well as lifetime energies
significant.
1
Rees, W. E. (1999). The Built Environment and Ecosphere: A Global Perspective.
Building Research and Information. British Columbia, William E Rees. 27: 206-220
2 Wallenvik, Olafur, Carbon Footprint of High Performance Versus Conventional Vibrated Concrete
2
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Drivers for Change
• Stakeholder demands for greater sustainability
– Brungart definition and triple bottom line.
– The precautionary principle & intergenerational equity
– Every improvement counts but paradigm improvements really matter – If
implemented!, but
– Quick fixes = paradigm changes
• Economic Cost Benefit given
– Rapidly rising energy costs
– Carbon taxes
• Construction activities contribute over 35% of total global CO2 emissions3 so carbon taxes will have
a big impact.
• > Sustainability can deliver > profit.
• Competition – Leed, the Green Building Council etc.
• Improved technical understanding and practice
• Government research and development as well as procurement policies
3UNEP
(2001). Energy and Cities: Sustainable Building and Construction Summary of Main Issues,
IETC Side Event at UNEP Governing Council, Nairobi, Kenya, UNEP.
3
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Sustainability?
The Techno Process
Primary Production Process Build, & Manufacture Use Dispose
Underlying Molecular Flows
Primary
Production
Methane
NOX &
SOX
Heavy
Metals
CO2
etc.
Embodied
& Process
Energy
Process,
Build
&
Manufacture
NOX &
SOX
Heavy
Metals CO2
etc.
Use
NOX &
SOX
Heavy
Metals
CO2
etc.
Lifetime
Energy
Embodied
& Process
Energy
Dispose
or Waste
Methane
NOX &
SOX
Heavy
Metals
CO2
etc.
Process
Energy
These are the releases and impacts we look at with LCA and LCCA
www.tececo.com
4
Predicted Global
Cement Demand and Emissions 4
4
Quillin K. Low-CO2 Cements based on Calcium Sulfoaluminate [Internet]. Available from:
http://www.soci.org/News/~/media/Files/Conference%20Downloads/Low%20Carbon%20Cements%20Nov%2010/Sulphoalumin
ate_Cements_Keith_Quillin_R.ashx
5
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Energy Outlook to 2035 5
5
U.S. Energy Information Administration. International Energy Outlook 2010 [Internet]. U.S.
Energy Information Administration; 2010 [cited 2010 Sep 5]. Available from:
www.eia.gov./oiaf/ieo/index.html
6
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Global Waste – An Underestimate!
The challenge is to convert waste to resource.
7
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Better more cost effective
concrete is more sustainable
• Concrete is not a perfect material yet. E.g. It shrinks, it cracks, it is not as
durable as we would like and has a limited range of properties.
– See how we fix many these issues in Part 2 - the section on reactive MgO
• Better concrete is not hard to make and there are huge opportunities for
change
• Improvements through innovation = Sustainable profit!
Increase in demand/price ratio for
sustainability due to educationally Supply
induced cultural drift.
$
ECONOMICS
Equilibrium
shift
Sustainable
profit
Demand
Increase in supply/price ratio for more sustainable products due to #
innovative changes in the technical paradigm.
8
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Paradigm
shifts ~ Lots
of little shifts!
Examples of Huge Change Opportunities
• A wide variety of possible end uses with higher potential margins for which
current solutions are sub-optimal.
– E.g. Addressing properties affecting lifetime energy.
• E.g. Mineral composites with higher “R” value
– E.g. Particle boards made with mineral binders
– E.g. Exterior structural panels with insulating properties
The use of Reactive
MgO makes this
possible. See Part 2
• Huge opportunities for reducing the cost base and improving the properties of
concretes by focusing on the process by which they are made and what they
are made with.
– A few tweaks to the formulations
– Major changes to the process and some
– Lateral thinking in relation to aggregates => Man made carbonate aggregate.
See Part 2 for the ramifications of using reactive MgO
• De-materialization through design (Reductions in Kg CO2-e/MPa, see Olafur
Wellevik’s presentation 7)
• Improvements in durability. Missing from the current analyses for sustainability
7
9
Wallenvik, Olafur, Carbon Footprint of High Performance Versus Conventional Vibrated Concrete
www.tececo.com
Innovation – Turning Buildings the Right Way Out
Mineral
composites with
low
conductance ~
high “R” value
and fire
resistance
Conventional
timber framing
and plaster
Mineral
composites with
high thermal
capacity
Mineral
composites with
high thermal
capacity
Mineral composites with high “R” value can easily be made using reactive magnesia because of the polar
bonding capacity (See Part 2). Hydration and carbonation products of reactive magnesia are all fire retardants.
Imagine the reduction in lifetime energies if we started constructing buildings the right way out!
10
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Increases in Business Performance
the Previous Year, by Innovation Status 2008-9
The technology paradigm defines
what is or is not a resource
11
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Barriers to Innovation and Change
•
Out of date and inappropriate legislative restriction.
–
•
See other presentations
A prescription rather than performance based standards and approvals system.
–
•
See Colin Lobo1 and Wassim Mansour3 and other presentations as well as what I have
to say.
A corrupt patent System.
–
–
•
Governments tend to issue patents to anyone for the money
A lack of know how in patent offices as a result of low pay
Conflicting
Lack of transparency in relation to new products.
–
•
Secret formulations more often than not in breach of other people’s intellectual property (ip).
Knowledge should be free
–
•
Wikipedia v Science Direct etc.
Green wash.
–
•
See other presentations
A focus on cost instead of cost effective
–
•
•
Little or no support for “cutting edge research” (See Lionel Lemay’s presentation4)
Conservatism (Goes without saying?)
A low level of skills in the industry
9
Lobo, Colin, The role of Performance Based Specification in Sustainable Development
Mansour, Wassim, Towards Performance-based Specification – Case Studies on Construction Projects in Abu Dhabi
11 Lemay, Lionel, Life cycle Assessment of Concrete Structures
10
12
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The Standards and Approvals Systems
• Far too often our standards and approvals ratings are
prescription based stifling innovation and change.
• Even Leeds in the US and the Green Building Council in
Australia make the same mistake
• Standards should be based on a list of metrics for
properties including embodied energy and emissions,
thermal capacity and conductance, strength
(compressive, shear and flexural) etc.
• This means that many existing standards should be
relegated to being “codes of practice”
• Proper audit process instead??
See Colin Lobo’s presentation (NRMCA)
13
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A Corrupt Global Patent System
• Patents are taken far to literally; the intent and purpose are
almost irrelevant.
• Most patent examiners are basically incompetent – How could
they be otherwise?
• The revenue raised is of greater importance to the grantee
government than the value of the so called monopoly rights
given.
• Patents are an invitation and challenge to others to steal ip.
– Many secret formulations end up being identified as stolen ip.
• Governments do not protect the ip they “grant” they let the
players fight it out in court.
• It follows that patents are little more than meat for dogs to fight
over.
– Consider geopolymers for example and my own experience.
14
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Is to plagiarize
really to be wise?
You can Patent Anything!
Fierce legal competition
over legal rights to
intellectual property
desperately needed by the
world is wrong.
Intelligent minds should
not be trapped into such a
resource consuming
process as defending their
intellectual property. A
rethink is required as new
technologies are essential
for the progress of
humanity and sustainability
into the future
http://www.google.com/patents?id=hhYJ
AAAAEBAJ&printsec=abstract&zoom=4#v
=onepage&q&f=false
15
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Cost rather than Profit Based
Business Models
• Most corporations in the concrete industry have
business model that relies on significant turnover and
cost cutting to deliver profit.
– Research and development budgets that deliver innovations
and potentially more profitable product are generally small.
If the industry believe in “cutting edge” research then they are going to have
to practice what they preach and support innovation.
In Australia there is now benchmark support for R & D and commercialisation
16
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Conservatism
• With the exception of perhaps the architectural fraternity players
in the construction industry are generally conservative
• There is little incentive and a lot of risk in using new materials
that have reduced embodied energies and emissions and
substantial impact on reducing lifetime energies.
• One of the reasons for this conservatism is the legal liability of
designers and engineers.
• Perhaps prescription standards should become codes of practice
and greater support given for testing of new materials.
• Audited procedures and less reliance on standards?
17
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The Low Level of Skills in the Industry
• There is an appallingly low level of skills in the concrete industry.
– Electricians and plumbers must have licenses in most countries yet
concrete placers and finishers seldom have any training at all.
– Most civil engineers are taught very little and understand less about the
material they use every day.
• It is no wonder we have the attitude that all that is grey is great,
all we make goes out the gate. (With affront meant to Grey
Matters)
– any diversion is risky!
• This terrible situation needs to change.
– Congratulations to the NRMCA re their producer training programs but
what about placers and finishers?
• Quality control should go beyond testing, it must include risk
management through training.
18
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Guides to Change - Abatement Potential
Paradigm Process Change??
12
Adapted from: Slide in presentation by Dr. John Ochsendorf, MIT Concrete Sustainability Hub (from
McKinsey Consulting 1999)
19
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Guides to Change - LCA and LCCA
Difficult and time consuming
but arguably essential. LCCA
much more relevant.
Issues relating to material
use. E.g. high embodied
energy and emissions of
aluminium could be offset
by the fact that aluminium is
often used to reduce
lifetime energy E.g.
aluminium awnings.
In Aust. aluminium has
around 80% recycled
content
20
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Embodied Energy and Emissions over Time
13
21
Source: Slide in presentation by Prof Roland Pellenq, MIT Concrete Sustainability Hub
www.tececo.com
Summary
• The use of Abatement Potential and LCA and in
particular LCCA should guide cost effective reductions in
embodied energy and emissions
• Cost effective reductions in lifetime energies
• De materialization (reduced over design)
• The MIT Sustainability Hub14 are probably the most
advanced
– Missing the impact of mineral composites made possible with
reactive MgO with properties other than high thermal
capacity such as “R” value
– Missing is any contemplation of paradigm changes. E.g. in the
way we make cements.
14
22
http://web.mit.edu/cshub/
www.tececo.com
Future Cement Contenders
Portland Cement
PC
Current
Methods
PC
Permeable
Block
.369
formulation
PC
Split Process
– Lime then .369
clinker
.369
0.498
0.498
0.498
.868
.868
.868
None
.369
.369
.001
.144
.001
Comment
.867
Split process
lime with
recapture then
clinker
No supplementary
Most dense cementitious or
pozzolanic
concretes
materials
1
.724
No supplementary
Ordinary
Most dense cementitious or
pozzolanic
Portland Cement concretes
materials
1
.368
Split process
lime with
recapture then
clinker
1
1. http://www.tececo.com/files/spreadsheets/TecEcoCementLCA12Oct2011.xls
23
Apply to
Notes
Cements
Process
Based on
Net
Absorpti Emissions
Emission on
(Sequestrat
Emissions s (kiln
(tonnes ion – No
Process
(if no kiln capture– CO2 /
kiln
CO2
Decarbonat
capture– tonnes
tonne
Capture)
(tonnes
ion CO2
tonnes
Compoun
Example of
CO2 /
CO2 /
(tonnes CO2
(tonnes
CO2 /
d,
Cement Type
tonne
tonne
/ tonne
CO
/
tonne
tonne
Compoun Assuming
2
Compound Compound)
Compound,
Compoun d)
100%
)
carbonati Assuming
d)
100%
on 1
carbonatio
year)
n 1 year)
www.tececo.com
No supplementary
Most dense cementitious or
pozzolanic
concretes
materials
The Potential of CO2 Release
and Capture - Portland Cements (+/- Tec-Kiln?)
No Capture during
Manufacture
CO2 capture (e.g.
N-Mg process etc.)
CO2 in atmosphere
Hydrated
Cement
Paste
H 2O
Clinker
Net Energy
3962 kJ/kg
product
Hydrated
Cement
Paste
Carbon positive. Chemical and
process emissions
Carbon positive. Chemical and
process emissions
H 2O
Net Energy
3962 kJ/kg
product
Clinker
Hydrated
Cement
Paste
24
CaO + Clays
Clinker
Net sequestration less carbon
from process emissions
Use of non fossil fuels => Low or no process emissions
15
CO2 capture (e.g.
N-Mg process etc.)
CaCO3
CaCO3 + Clays
CaCO3 + Clays
Net Energy
3962 kJ/kg
product
Net Emissions
(Sequestration) 0.369
Kg CO2/Kg product
Net Emissions
(Sequestration) 0.369
kg CO2/kg product
Net Emissions
(Sequestration) 0.867
kg CO2/kg product
H 2O
Split Process with
Capture during
Manufacture
Capture during
Manufacture
Source Data: http://www.tececo.com/files/spreadsheets/TecEcoCementLCA12Oct2011.xls
Future Cement
Contenders - Mg Group
Absorpti
on
(tonnes
CO2 /
tonne
Compou
nd,
Assumin
g 100%
carbonati
on 1
year)
Net
Emission
s
(Sequestr
ation)
(tonnes
CO2 /
Example of Cement
tonne
Apply to
Type
Compou
nd,
Assumin
g 100%
carbonati
on 1
year)
Cements
Process
Based on
Emission
Emission
s (kiln
Decarbona s (if no
capture–
Process
tion CO2 kiln
tonnes
CO2
(tonnes
capture–
CO2 /
(tonnes
CO2 /
tonnes
tonne
CO2 / tonne tonne
CO2 /
Compou
Compound) Compoun tonne
nd)
Compou
d)
nd)
<750 oC
MgCO3
.403
1.092
1.495
.403
-1.092
.-.688
Eco-cement concrete,
TecEco Eco-Cement
TecEco, Cambridge
pure MgO concretes.
Force carbonated
& Novacem
Novacem concretes
pure MgO
1
<450 oC
MgCO3.3H2O
.693
1.092
1.784
.693
-1.092
-.399
Eco-cement concrete,
TecEco, Cambridge N-Mg route
pure MgO concretes.
& Novacem
University of Rome
Novacem concretes?
1
.693
1.092
1.784
.693
-2.184
-1.491
Eco-cement concrete,
TecEco, Cambridge N-Mg route
pure MgO concretes.
& Novacem
University of Rome
Novacem concretes?
1
<450 oC
Modified
Ternary
Blends
(50% PC)
MgCO3.3H2O
Including
capture during
production of
nesquehonite
Silicate route
Split Process –
Lime (with
capture) then
clinker
?
Novacem
.185
.185
.002
.183
Ternary mix with MgO Most dense
additive.
concretes
1. http://www.tececo.com/files/spreadsheets/TecEcoCementLCA12Oct2011.xls
2. http://www.tececo.com/files/newsletters/Newsletter93.php
25
www.tececo.com
Notes
Comment
After Klaus Lackner?
Faster setting and
2
higher early strength
The Potential of CO2 Release
and Capture - Magnesite (MgCO3) Route
No Capture during
Manufacture
With Capture during
Manufacture
<7250C
CO2
CO2 from
atmosphere
Net Emissions
(Sequestration)
0.403 Kg CO2/Kg
product
Net Emissions
(Sequestration) .085 kg
CO2/kg product
MgCO3
MgCO3
H2O
H2O
Net Energy
4084 kJ/kg
product
MgO
H2O
Net Energy
4084 kJ/kg
product
MgO
H2O
H2O
Carbon neutral except for carbon from
process emissions
Net sequestration less carbon from
process emissions
Use of non fossil fuels => Low or no process emissions
16
H2O
Mg(OH)2
Mg(OH)2
26
CO2 capture
(e.g. N-Mg
process etc.)
Source Data: http://www.tececo.com/files/spreadsheets/TecEcoCementLCA14Feb2011.xls
The Potential of CO2 Release
and Capture - Nesquehonite (MgCO3.3H2O) Route
No Capture during
Manufacture
With Capture during
Manufacture
<4200C
CO2
CO2 from
atmosphere
Net Emissions
(Sequestration)
0.693 Kg CO2/Kg
product
H2O
H2O
MgO
H2O
H2O
Net Energy
7140 kJ/kg
product
H2O
H2O
Carbon neutral except for carbon from
process emissions
Net sequestration less carbon from
process emissions
Use of non fossil fuels => Low or no process emissions
17
MgO
Mg(OH)2
Mg(OH)2
27
CO2 capture
(e.g. N-Mg
process etc.)
MgCO3.3H2O
MgCO3.3H2O
Net Energy
7140 kJ/kg
product
Net Emissions
(Sequestration) .399kg CO2/kg
product
Source Data: http://www.tececo.com/files/spreadsheets/TecEcoCementLCA14Feb2011.xls
Gaia Engineering
kg CO2-e/kg product
1 -1.092
2 -.399
3 -1.092
>2 kg CO2-e/kg Mg
product
2
3
1
Or similar. The annual world production of HCl is about 20
million tons, most of which is captive (about 5 million tons
on the merchant market).
28
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Man Made Carbonate
Aggregate?
Tonnes 20,000,000,000
18,000,000,000
16,000,000,000
World Production PC
14,000,000,000
Tonnes CO2 from unmodified PC
12,000,000,000
World Production Concrete
10,000,000,000
8,000,000,000
Calculated Proportion Aggregate
6,000,000,000
4,000,000,000
CO2 Sequestered in Mg Carbonate
Aggregate
2,000,000,000
Net Sequestration
2009
2006
2003
2000
1997
1994
1991
1988
1985
1982
1979
1976
1973
1970
1967
1964
1961
1958
1955
1952
1949
1946
0
Assumptions - 50% non PC N-Mg mix and Substitution by Mg Carbonate Aggregate
Percentage by Weight of Cement in Concrete
Percentage by weight of MgO in cement
Percentage by weight CaO in cement
Proportion Cement Fly ash and/or GBFS
1 tonne Portland Cement
Proportion Concrete that is Aggregate
CO2 captured in 1 tonne aggregate
29
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Source USGS: Cement Pages
15.00%
6%
29%
50%
0.867Tonnes CO2
85%
1.092Tonnes CO2
Magnesium Carbonate Cements
• Magnesite (MgCO3) and the di, tri, and pentahydrates known as barringtonite
(MgCO3·2H2O), nesquehonite (MgCO3·3H2O), and lansfordite (MgCO3·5H2O),
respectively.
• Some basic forms such as artinite (MgCO3·Mg(OH)2·3H2O),
hydromagnestite (4MgCO3·Mg(OH)2·4H2O) and dypingite (4MgCO3·
Mg(OH)2·5H2O) also occur as minerals.
• We pointed out as early as 2001 that magnesium carbonates are ideal for
sequestration as building materials mainly because a higher proportion of CO2
than with calcium can be bound and significant strength can be achieved.
• The significant strength is a result of increased density through carbonation
(high molar volume increases) and the microstructure developed by some
forms.
TecEco Eco-Cements have relatively high proportions of magnesia which in
permeable materials carbonates forming lansfordite and nesquehonite
adding strength and durability. Eco-Cement formulations are generally used
for bricks, blocks, pavers, pervious pavements and other permeable cement
based products. See http://www.tececo.com/products.eco-cement.php
30
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TecEco Non-Carbonating Tec-Cements
Tec-Cements are cement blends that comprise of a hydraulic cement such as Portland cement mixed with a
relatively small proportion of reactive magnesia and optionally pozzolans and/or supplementary cementitious
materials which react with Portlandite removing it and making more cement or are activated by Portland cement.
They offer a solution to many of the technical problems that plague traditional cement formulations caused by the
reactivity of lime (Portlandite) and have significant advantages including faster setting even with a high proportion of
non PC additions. See http://www.tececo.com/products.tec-cement.php
Tec-Cement Ternary Blends
15-30% improvement in strength
Fast first set & better rheology
Less shrinkage – less cracking, less bleeding,
greater long term durability, Solve autogenous
shrinkage?
Criteria
Energy Requirements and Chemical Releases,
Reabsorption (Sequestration?)
Speed and Ease of Implementation
Barriers to Deployment
Cost/Benefit
Use of Wastes? or Allow Use of Wastes?
Performance
Engineering
Thermal
Architectural
Safety
31
Good
Bad
Use >50% replacements and still set like
“normal” concrete!
Rapid adoption possible
Permissions and rewards systems see
http://www.tececo.com/sustainability.permissions
_rewards.php
Excellent until fly ash runs out!
Uses GBFS and fly ash and manufactured
nesquehonite based aggregate
Excellent all round
High thermal capacity
Excellent
No issues
www.tececo.com
Magnesium Phosphate Cements
• Chemical cements that rely on the precipitation of insoluble magnesium
phosphate from a mix of magnesium oxide and a soluble phosphate.
• Some of the oldest binders known (dung +MgO)
• Potentially very green
– if the magnesium oxide used is made with no releases or via the nesquehonite (NMg route) and
– a way can be found to utilise waste phosphate from intensive agriculture and
fisheries e.g. feedlots. (Thereby solving another environmental problem)
Criteria
Energy Requirements and Chemical Releases,
Reabsorption (Sequestration?)
Speed and Ease of Implementation
Barriers to Deployment
Cost/Benefit
Use of Wastes? or Allow Use of Wastes?
Performance
Engineering
Thermal
Architectural
Safety
32
Good
Bad
The MgO used could be made without releases
Rapid adoption possible
There is not much phosphate on the planet
If barrier overcome (see below)
Permissions and rewards systems see
http://www.tececo.com/sustainability.permissions_re
wards.php. Must find a way to extract phosphate from
organic pollution.
Economies of scale issue for MgO to overcome
With technology could use waste phosphate
reducing water pollution
Excellent all round
High thermal capacity
No issues
www.tececo.com
Sorel Type Cements and Derivatives
Sorel Type Cements and Derivatives are all nano
or mechano composites relying on a mix of ionic,
co-valent and polar bonding.
There are a very large number of permutations
and combinations and thus a large number of
patents
Criteria
Good
Energy Requirements and Chemical Releases,
Reabsorption (Sequestration?)
The MgO used could be made without releases
Speed and Ease of Implementation
More could be used
Barriers to Deployment
Cost/Benefit
Economies of scale issue for MgO to overcome
Use of Wastes? or Allow Use of Wastes?
Performance
Engineering
Excellent except
Thermal
High thermal capacity
Architectural
Safety
No issues
33
www.tececo.com
Bad
If barrier overcome (see below)
Not waterproof even with modification.
Not waterproof
Not waterpoof, salt affect metals
Future Cement Contenders
(tonnes
CO2 /
Example of
tonne
Cement Type
Compoun
d,
Assuming
100%
carbonati
on 1 year)
0.785
-0.332
>0.578
>0.511
?
?
>0.578
>0.511
0.594
>0.594
?
>0.594
0.216
>0.216
?
?
CaO
Conventional .453
0.785
1.237
C3S
C2S
Conventional ?
Conventional ?
0.578
0.511
C3A
Conventional ?
C4A3S
Conventional ?
.453
Net
Emissions
(Sequestr
ation)
Carbonating
lime mortar
Apply to
Comment
Notes
Cements
Process
Based on
Absorpt
ion
Emission
Emission
(tonnes
Decarbon
s (kiln
s (if no
CO2 /
ation
capture–
Process
kiln
tonne
CO2
tonnes
CO2
capture–
Compou
(tonnes
CO2 /
(tonnes CO2
tonnes
nd,
CO2 /
tonne
/ tonne
CO2 /
Assumi
tonne
Compou
tonne
ng
Compound)
Compoun
nd)
Compou
100%
d)
carbona
nd)
tion 1
year)
Small net
Calera, British Lime sequestration
Assn. & many others with TecEco
kiln
Belite cement Chinese & others
Tri calcium
aluminate
Increased proportion
cement
Calcium
sulfoaluminate Chinese & others
cement
1. http://www.tececo.com/files/spreadsheets/TecEcoCementLCA12Oct2011.xls
3. Quillin, K. and P. Nixon (2006). Environmentally Friendly MgO-based cements to support sustainable construction - Final report, British Research
Establishment.
34
www.tececo.com
1
3
3
3
Future Cement Contenders
Cements
Based on
Process
Alakali
Activated
Ground
Granulate
d Blast
Furnace
Slag
(GBFS)
GBFS
(“slag”) is
a waste
product
Nil to
from the cement
manuf
industry
acture of
iron and
steel
Net
Emissions
(Sequestr
ation)
(tonnes
CO2 /
Example of
tonne
Cement Type
Compoun
d,
Assuming
100%
carbonati
on 1 year)
Apply to
Comment
Notes
Absorpt
ion
Emission
Emission
(tonnes
Decarbon
s (kiln
s (if no
CO2 /
ation
capture–
Process
kiln
tonne
CO2
tonnes
CO2
capture–
Compou
(tonnes
CO2 /
(tonnes CO2
tonnes
nd,
CO2 /
tonne
/ tonne
CO2 /
Assumi
tonne
Compou
tonne
ng
Compound)
Compoun
nd)
Compou
100%
d)
carbona
nd)
tion 1
year)
GBFS with
MgO activator
Patented by
TecEco
Many other
activators
1
Not patented
Geopolymer Alliance,
Geo
polymers
Fly ash +
NaOH
0.16
0.16
1. http://www.tececo.com/files/spreadsheets/TecEcoCementLCA12Oct2011.xls
4. http://www.geopolymers.com.au/science/sustainability
35
www.tececo.com
Geopolymer
Institute, University
Melbourne
6
CaO-Lime
Criteria
Good
Energy Requirements and Chemical Releases,
Reabsorption (Sequestration?)
The CaO used could be made without
Speed and Ease of Implementation
Barriers to Deployment
Cost/Benefit
Use of Wastes? or Allow Use of Wastes?
Performance
Engineering
Thermal
Architectural
Safety
Audience 1
Audience 2
36
Easily implemented as no carbonation rooms etc.
reqd.
Good
Engineered thermal capacity and conductivity.
An irritating dust
www.tececo.com
Bad
Permissions and rewards systems see
http://www.tececo.com/sustainability.permissions_rewa
rds.php.
Geopolymers
Criteria
Good
Energy Requirements and Chemical Releases,
Reabsorption (Sequestration?)
Low provided we do not run out of fly ash
Speed and Ease of Implementation
Barriers to Deployment
Cost/Benefit
Use of Wastes? or Allow Use of Wastes?
Performance
Engineering
Thermal
Architectural
Safety
Audience 1
Audience 2
Process issues to be overcome
Bad
Permissions and rewards systems see
http://www.tececo.com/sustainability.permissions_rewa
rds.php.
Good but inconsistent
Engineered thermal capacity and conductivity.
Caustic liquors
Geopolymers as a future concrete suffer from two basic flaws on one very high risk
Flaw. 1. The nanoporisity flaw which leads to durability problems and
Flaw. 2. The fact that water is not consumed in the geopolymerisation process resulting in
the almost impossible task of making them fluid enough for placement.
Risk. Too much water reduces alkalinity and results in a high risk.
37
www.tececo.com
Other Contenders
• Slag cements a variant of Portland cement as CSH is the main product.
• Supersulfated cements have potential as they are made mostly from GBFS and
gypsum which are wastes and only a small amount of PC or lime. The main
hydration product is ettringite and they show good resistance to aggressive
agents including sulphate but are slow to set. (A derivative)
• Calcium aluminate cements are hydraulic cements made from limestone and
bauxite. The main components are monocalcium aluminate CaAl2O4 (CA) and
mayenite Ca12Al14O33 (C12A7) which hydrate to give strength. Calcium
aluminate cements are chemically resistant and stable to quite high
temperatures.
• Calcium sulfoaluminate cements & belite calcium sulfoaluminate cements
are low energy cements that have the potential to be made from industrial by
products such as low calcium fly ash and sulphur rich wastes. The main
hydration product producing strength is ettringite. Their use has been
pioneered in China (A derivative)
• Fly ash Cements based on Class C fly ash. As this type of fly ash varies it has
been difficult to produce a consistent product.
38
www.tececo.com
Other Contenders
• Belite cements can be made at a lower temperature and contains less lime
than Portland cement and therefore has much lower embodied energy and
emissions. Cements containing predominantly belite are slower to set but
otherwise have satisfactory properties. Many early Portland type cements
such as Rosendale cement were rich in belite like phases. (a variant, See
http://www.tececo.com/links.cement_rosendale.php.)
• PC - MgO – GBFS – fly ash blends. MgO is the most powerful new tool in
hydraulic cement blends since the revelation that reactive magnesia can be
blended with other hydraulic cements such as Portland cement. 25-30%
improvements in compressive strength and greater improvements in tensile
strength, faster first set, better rheology and less shrinkage and cracking less
bleeding and long term durability have been demonstrated. It is also possible
autogenous shrinkage has been solved.
• MgO blended with other hydraulic cements, pozzolans and supplementary
cementitious materials (SCM’s). Amazingly very little real research has been
done on optimised blends particularly with cements other than Portland
cement. 18
See also: Sanjayan, Jay, Recent advances in geopolymer and other non-Portland
based cements. Proc. Concrete 2011, CIA.
39
www.tececo.com
Summary –Mehta’s Triangle
30%
saving
in
cement
50%
saving
in
clinker
1.
Consume less
concrete
Dematerialisation
2.
Consume less
cement
Longer period for
strength, better particle
packing. Etc.
2.
Consume less
clinker
Replacement by
pozzolans and SCA’s
19
Mehta, P.K., 2009. Global Concrete Industry Sustainability.
Concrete International, Vol 31(2), p.4.
40
www.tececo.com
Harrison’s Table
Criteria
Description
Players
Drivers
Economic
cost/benefit,
Sustainability,
Leed, GBC, R
&D&
Procurement
Policies.
Barriers
Prescription standards and
approvals systems
(see http://www.tececo.co
Innovative architecture and engineering. More
Architects &
m/sustainability.permission
Dematerialisation durable concretes.
Engineers
s_rewards.php.)
Conservatism, inappropriate
software. Prescription
standards and approvals
systems
Appropriate particle packing, better admixtures and
(see http://www.tececo.co
Economic
use of brucite hydrates to release water for more
Cement
m/sustainability.permission
cost/benefit,
Optimisation
complete hydration
technologists sustainability. s_rewards.php.)
Blended cements that contain a high volume of
Conservatism, out dated
Economic
replacement materials such as fly ash, slag cement
software. Prescription
cost/benefit,
(gbfs), pozzolans, silica fume, rice husk ash etc. High
Sustainability, standards and approvals
Replacement of
replacement cement concretes often have improved
Leed, GBC, R systems
cement by
properties such as rheology, less shrinkage, greater
(see http://www.tececo.co
&D&
pozzolans and
durability etc. The use of reactive MgO makes the
Cement
m/sustainability.permission
Procurement
SCA’s
use of higher proportions possible.
technologists Policies.
s_rewards.php.)
Alternative
Cements that involve calcination can be made
processes of
without releases. One option is to split the process,
Sustainability, Inability to think outside the
manufacture
another is to use closed system kilns
Scientists
carbon taxes. box. Fear of change
Mineral composites other than concrete with just
Alternative
stone aggregate would be useful. E.g. composites
Materials
Inability to think outside the
Economic
product
with a high “R” value
scientists
box. Fear of change
cost/benefit
Alternative
emphasis
41
An emphasis other than on the binder to improve
sustainability. E.g. Use of man made carbonate
aggregate.
Scientists
Guides
Design codes,
LCA & LCCA
Mix design
methods. LCA &
LCCA. New
better software.
Mix design
methods. LCA &
LCCA. New
better software.
Common sense!
Standards, LCA
& LCCA
Sustainability,
Inability to think outside the
Economic
box. Fear of change.
cost/benefit.
Common sense!
Technical merit Technical issues (?).
www.tececo.com
Part2
The Role of Reactive MgO – An
Update on TecEco Technology
An update on recent advances in Tec and EcoCements including the use of high proportions of
fly ash and SCMS with added reactive magnesia
Reactive Magnesia is the most powerful
new tool in cement chemistry
42
www.tececo.com
www.tececo.com
TecEco Patents
• Reactive magnesia (calcined at less than about 750 0C)
included in a hydraulic composition with or without
added pozzolans. They may or may not carbonate.
• We define in most jurisdictions hydraulic cements
according to the ASTM C219-94 definition as “a cement
that sets and hardens by chemical interaction with
water and that is capable of doing so under water”
• We include slag cements as hydraulic and notice the
American Slag Association think likewise.
• Beware of imitators and charlatans
43
www.tececo.com
TecEco Cements
• Eco-Cements have relatively high proportions of magnesia which in permeable
materials carbonates adding strength and durability. Eco-Cement formulations are
generally used for bricks, blocks, pavers, pervious pavements and other permeable
cement based products. See http://www.tececo.com/products.eco-cement.php
• Enviro-Cements are made using large quantities of reactive magnesia which reacts to
form brucite. Brucite is unique to TecEco Cements and is an ideal mineral for trapping
toxic and hazardous wastes due to its layered structure, equilibrium pH level, durability
and low solubility. See http://www.tececo.com/products.enviro-cement.php
• Tec-Cements are cement blends that comprise of a hydraulic cement such as Portland
cement mixed with a relatively small proportion of reactive magnesia and optionally
pozzolans and/or supplementary cementitious materials which react with Portlandite
removing it and making more cement or are activated by Portland cement. They offer a
solution to many of the technical problems that plague traditional cement formulations
caused by the reactivity of lime (Portlandite) and have significant advantages including
faster setting even with a high proportion of non PC additions. See
http://www.tececo.com/products.tec-cement.php
44
www.tececo.com
Magnesium Minerals
Mineral
Formula
Class
Molar Hard
volume ness
Habit
Brucite
Mg(OH)2
Brucite
24.40
Blocky pseudo hexagonal crystals.
http://webmineral.com/Alphabetical_Li
Platy or foliated masses and rosettes - fibrous to sting.shtml
http://en.wikipedia.org/wiki/Brucite
massive
Notes 1, 2, 3
Brucite
Hydrates
Mg(OH)2.nH2O
brucite ?
hydrates
2.5
Not much known about them!
http://webmineral.com/Alphabetical_Li
sting.shtml
http://mineralbliss.blogspot.com/2010/
03/different-pokrovskite-habitspossible.html
http://webmineral.com/Alphabetical_Li
sting.shtml
Pokrovskite Mg2(CO3)(OH)2·0.5(H2O)
Basic
66.79
3
Brown radiating tufts.
Artinite
Basic
105.81
2.5
Bright, white acicular sprays
Forms crusts of acicular crystals, elongated
[010]. Also botryoidal masses of silky fibres;
spherical aggregates of radiating fibers; crossfibre veinlets.
Mg2(CO3)(OH)2•3(H2O)
Hydromagn Mg5(CO3)4(OH)2.4H2O
esite
Dypingite
45
Mg5(CO3)4(OH)2.5H2O
Basic
Basic
221.86
181.45
Reference for Habit
3.5
Include acicular, lathlike, platy and rosette
forms
Crystals small, occurring as tufts, rosettes, or
crusts of acicular or bladed crystals elongated
[001] and flattened {100}. Massive, chalky.
181.45 Numerous individual crystals or clusters.
Globular - Spherical, or nearly so, rounded
forms (e.g. wavellite).
www.tececo.com
http://www.mindat.org/min-377.html
http://webmineral.com/Alphabetical_Li
sting.shtml
http://www.mindat.org/show.php?id=1
979&ld=1
http://webmineral.com/data/Dypingite
.shtml
Magnesium Minerals
Mineral
Formula
Class
Giorgiosite
Mg5(CO3)4(OH)2 Basic
.5-6H2O
Magnesite
MgCO3
Barringtonite
Molar Hard Habit
volume ness
Reference for Habit
183.93
3.5
Fibrous and spherulitic, admixed with other
species in powdery masses.
http://www.mindat.org/min1979.html
Normal or 28.11
“self
setting”
3.9
Usually massive
Crystals usually rhombohedral {1011}, also
{0112}; prismatic rare [0001] with {1120} and
{0001}, or tabular {0001}. Scalenohedral rare.
Massive, coarse- to fine-granular, very compact
and porcelainous; earthy to rather chalky;
lamellar; coarsely fibrous
http://webmineral.com/Alphabetical_L
isting.shtml
http://www.mindat.org/min2482.html
MgCO3·2H2O
Normal or 42.53
“self
setting”
2.5
Glassy blocky crystals
http://webmineral.com/Alphabetical_L
isting.shtml
Nesquehonite MgCO3·3H2O
Normal or 74.79
“self
setting”
2.5
Acicular prismatic needles
Crystals prismatic, elongated along [010], {001},
{010}, {011}, {101}. {110} deeply striated parallel
to [010]. Forms radial sprays and coatings, also
botryoidal.
http://webmineral.com/Alphabetical_L
isting.shtml
http://www.mindat.org/min2885.html
Lansfordite
Normal or 102.59
“self
setting”
2.5
Glassy blocky crystals
Minute short-prismatic crystals [001]; also
stalactitic.
http://webmineral.com/Alphabetical_L
isting.shtml
http://www.mindat.org/min2324.html
46
MgCO3·5H2O
www.tececo.com
The N-Mg Process for
MgO Cement and Aggregate Production
kg CO2-e/kg product
1 -1.092
2 -.399
3 -1.092
>2 kg CO2-e/kg Mg
product
2
3
1
Or similar. The annual world production of HCl is about 20
million tons, most of which is captive (about 5 million tons
on the merchant market).
47
www.tececo.com
The N-Mg Process
HCl
NH3 and a small amount of CO2
CO2
H2O
Tec-Kiln
Mg rich water
Ammoniacal Mg rich water
MgCO3.3H2O
MgO
MgO
Mg(OH)2
Steam
MgCO3.3H2O
Filter
Filter
NH4Cl and a small amount of NH4HCO3
The N-Mg Process - A Modified Solvay Process for Nesquehonite
48
www.tececo.com
Gaia Engineering
Portland Cement
Manufacture
CaO
TecEco
Tec-Kiln
Industrial CO2
Brine,
Sea
water,
Oil
Process
water,
De Sal
Waste
Water
etc .
N-Mg
Process
MgO
MgCO3.3H2O
TecEco
Cement
Manufacture
GBFS
Fly ash
Fresh
Water
EcoCements
NH4Cl or HCl
Building
components &
aggregates
Other wastes
49
Clays
www.tececo.com
TecCements
The TecEco Tec-Kiln
An obvious future requirement will be to make cements without releases so
TecEco are developing a top secret kiln for low temperature calcination of alkali
metal carbonates and the pyro processing and simultaneous grinding of other
minerals such as clays.
The TecEco Tec-Kiln makes no releases and is an essential part of TecEco's plan to
sequester massive amounts of CO2 as man made carbonate in the built
environment .
The TecEco Tec-Kiln has the following features:
• Operates in a closed system and therefore does not release CO2 or other
volatiles substances to the atmosphere
• Can be powered by various potentially cheaper non fossil sources of energy
such as intermittent solar or wind energy.
• Grinds and calcines at the same time thereby running 25% to 30% more
efficiently.
• Produces electricity as a by-product.
• Can be integrated into an industrial ecology producing solid fuel
• Produces more precisely definable product. (Secret as disclosure would give
away the design)
• The CO2 produced can be sold or re-used in for example the N-Mg process.
• Cement made with the Tec-Kiln will be eligible for carbon offsets.
To further develop the Tec-Kiln, TecEco require not only additional
funding but also partners able to provide expertise.
50
www.tececo.com
TecEco Tec-Kiln, N-Mg route
The calcination of nesquehonite has a relatively
high enthalpy but there is significant scope for
reducing energy using waste heat and for cogeneration from expansive gas emissions.
Initial weight loss below 1000 C consists almost
entirely of water (1.3 molecules per molecule of
nesquehonite). Between 100 and 1500C
volatilization of further water is associated with
a small loss of carbon dioxide (~3-5 %).
From 1500C to 2500C, the residual water
content varies between 0-6 and 0-2 molecules per
molecule of MgC03. Above 3000C, loss of
carbon dioxide becomes appreciable and is
virtually complete by 4200C, leaving MgO with a
small residual water content.
1
Dell, R. M. and S. W. Weller (1959). "The Thermal
Decomposition of Nesquehonite MgCO3.3H20 And
Magnesium Ammonium Carbonate MgCO3 (NH4)2CO3
4H2O." Trans Faraday Soc 55(10): 2203 - 2220.
51
Energy could be saved using a two stage calcination
process using waste energy for the first stage.
www.tececo.com
TecEco Eco-Cements
Eco-Cements are blends of one or more
hydraulic cements and relatively high
proportions of reactive magnesia with or
without pozzolans and supplementary
cementitious additions. They will only
carbonate in gas permeable substrates forming
strong fibrous minerals such as lansfordite and
nesquehonite. Water vapour and CO2 must be
available for carbonation to ensue.
Light colour = low albido
Eco-Cements can be used in a wide range of
products from foamed concretes to bricks,
blocks and pavers, mortars renders, grouts and
pervious concretes such as our own
permeacocrete. Somewhere in the vicinity of
the Pareto proportion (80%) of conventional
concretes could be replaced by Eco-Cement.
Left: Recent Eco-Cement blocks made, transported and erected in a week.
Laying and Eco-Cement floor. Eco-Cement mortar & Eco-cement mud
bricks. Right: Eco-Cement permeacocretes and foamed concretes
52
www.tececo.com
Forced Carbonation ~ Optimisation
Forced Carbonation (Cambridge)
Kinetic Optimisation (TecEco)
Steps
Multistep process
Less steps = lower costs
Rate
Variable
Varying on weather conditions (wet dry best and gas
permeability)
% Carbonation in 6 months
70% (reported, could be more if
permeable)
100%
Ease of general
implementation
Require point sources CO2
Can be implemented very quickly
Can use large quantities of
fine wastes
Can use large quantities of fine wastes like
fly ash that are not necessarily pozzolanic
Fine wastes tend to reduce gas permeability
Safety
Are carbonation rooms safe?
No issues
Key requirements
Special carbonation rooms
Optimal kinetics including gas permeability
Doubling the concentration of CO2 doubles
the rate of carbonation.
Able to be sealed with paint etc. as pre
carbonated
Doubling the pore size quadruples the rate of
carbonation.
Physical rate considerations
Other issues
Some sealing paints will slow down carbonation
2
According to ECN "The CO2 concentration in power station flue gas ranges from about 4% (by volume)for natural gas fired
combined cycle plants to about 14% for pulverised coal fired boilers." At 10% the rate increase over atmospheric could be
expected to be 10/.038 = 263 times provided other kinetic barriers such as the delivery of water do not set in. Ref:
http://www.ecn.nl/en/h2sf/products-services/co2-capture/r-d-activities/post-combustion-co2-capture/ accessed 24 Mar 08.
Forced carbonation of silicate phases as promoted by some is nonsense
53
www.tececo.com
Carbonation Optimisation
•
Dissolution of MgO
– Gouging salts e.g. MgSO4, MgCl2 and NaCl
(Not used by TecEco)
– Various catalysing cations e.g. Ca ++ and Pb ++
and ligands EDTA, acetate, oxalate citrate etc.
(Not used by TecEco)
– Low temperature calcination = Low lattice
energy = high proportion of unsaturated
co-ordination sites = rapid dissolution.
See http://www.tececo.com/technical.reactive_magnesia.php
•
•
•
•
•
54
Carbonation – High concentration of CO3-at high pH as a result of OH- from Portlandite
Possible catalysis and nucleation by polar
surface of calcium silicate hydrate at high pH
Wet dry conditions. Wet for through
solution carbonation, dry for gas transport.
Gas permeability
Carbonate shape is important (next slides)
www.tececo.com
Particle Packing – Percolation and Porosity ~
Permeability
Shape effects
particle packing
(Olafur Wallevik
presentation3 )
and the angle of
repose (Bagnold4).
The latter is
therefore a proxy
guide to shape.
Eco-Cements are
deliberately not
perfectly packed.
Whereas in TecCements the
opposite occurs
3Wallenvik,
Olafur, Carbon Footprint of High Performance Versus Conventional Vibrated Concrete
A, The Physics of Blown Sand and Desert Dunes
4Bagnold, Ralph
55
www.tececo.com
Why Nesquehonite as a
Binder in Eco-Cements / Aggregate?
•
•
•
•
•
•
•
•
•
Significant molar volume expansion.
Excellent morphology. Nesquehonite has an ideal shape that contributes
strength to the microstructure of a concrete
Forms readily at moderate and high pH in the presence of CSH. (Catalytic
nucleation mechanism?)
Can be manufactured using the N-Mg Process
Can be agglomerated
Light albido
Stable over a wide PT range (See Ferrini’s work)
The hydration of PC => alkalinity dramatically increasing the
CO3-- levels that are essential for carbonation.
Captures more CO2 than Calcium
CO 2
44
CO 2
44

 43%

 52%
CaCO3
101
MgCO 3
84
Nesquehonite courtesy of Vincenzo
Ferrini, university of Rome.
pH dependent speciation
3H2O + CO3---- + Mg++ => MgCO3·3H2O
•
XRD Pattern Nesquehonite
Ideal wet dry conditions are easily and cheaply provided. Forced
is not required
(Cambridge
andinothers)
Wecarbonation
have to ask ourselves
why we are
still digginguni
holes
the ground. The industry would
encounter far less bureaucratic blocking, make more money and go a long way towards
solving global warming by manufacturing out of Mg, thin air and water its own inputs!
56
www.tececo.com
Economics of Magnesium
Carbonate Binder Based Masonry Products
7mm Basalt
3mm Dust
Bottom Ash
Total Aggregate
Total Batch
Water (litres)
Total
Binder Costs
Cost PC
Cost MgO
Sub Total
Less Carbon credit
Net Cost Binder
57
310
190
660
1160
1360
80
1440
310
190
660
1160 80.56%
1360
80
1440
Normal
(kg)
200
Material
PC
Reactive MgO
Total Cementitous
Assuming
GP Cement
Reactive MgO
Value Carbon Capture
% PC Capture
% MgO Capture
200
EcoCement
(kg)
80
120
200 13.89%
$90.00
$0.00
$90.00
$1.45
$88.55
$
$
$
0.45
0.75
0.025
29.00%
100.00%
$36.00
$90.00
$126.00
$3.58
$122.42
Actual
0.45
Kg $
0.75
Kg $
0.025
Kg $
%
%
This embedded spread sheet looks only at the binder price and
assumes all other factors remain the same
What this embedded spread
sheet demonstrates is that
Magnesium Carbonate Block
formulations are uneconomic
unless the price of reactive MgO
approaches that of PC or there is
a high price for carbon or
alternatively less MgO can be
used!
Because of molar volume growth
less can be used but we must still
address supply chain issues.
Permeacocretes
•
•
•
58
Permeacocretes are an example of
a product where the other
advantages of using reactive MgO
overcome its high cost.
The use of MgO gives an ideal
rheology which makes it possible to
make permeacocrete pervious
pavements using conventional road
laying equipment therefore
substantially reducing labour costs.
There are many other advantages
of pervious pavements see
http://www.tececo.com/files/confe
rence%20presentations/TecEcoPres
entationSGA25Mar2010.ppt
www.tececo.com
Tec-Cements
• Tec-Cements (5-20% MgO, 80-95% OPC)
– contain more Portland cement than reactive magnesia.
Reactive magnesia hydrates in the same rate order as Portland
cement forming Brucite which uses up excess water reducing
the voids:paste ratio, increasing density and possibly raising
the short term pH.
– Reactions with pozzolans are more affective. After much of
the Portlandite has been consumed Brucite tends to control
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 many of which are potentially
wastes without reaction problems.
59
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Water – Fundamental to Concretes
Polar Bonding
-O--
H+
H+
Diagrammatic
representation of a water
molecule having polar
covalent bonds between
the Oxygen atom and the
Hydrogen atoms. (Note the
angle is 104.5 oC)
In a polar covalent bond, the electrons shared by the atoms spend a greater amount of
time, on average, closer to the oxygen nucleus than the hydrogen nucleus. This is
because of the geometry of the molecule and the great electronegativity difference
between the hydrogen atom and the oxygen atom.
The result of this pattern of unequal electron association is a charge separation in the
molecule, where one part of the molecule, the oxygen end, has a partial negative
charge and the hydrogen's have a partial positive charge.
These drawings are subject to copyright by TecEco
60
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The Electrostatic Nature of Cements made with Water
The surface tension of water is 73 dynes per cm at 18oC compared to ethyl alcohol
at 24 dynes per cm.
Hydrogen bonding is attributed to the ability of water to adhere to or “wet” most
surfaces; such substances are said to be hydrophilic (water-loving). Hydrogen
bonding is only about 10 per cent of the strength of the covalent bond, but it is
responsible for most of the unusual properties of water (high freezing and boiling
points, high heat capacity, high heats of fusion and evaporation, solvency, and
high surface tension).
Water has an exceptionally large dipole moment (1.87 x 10-18 e.s.u.) relative to
most other inorganic compounds. Dipole moment is the product of the distance
between the charges multiplied by the magnitude of the charge in electrostatic
units (e.s.u.).
5Refer:
Labbe, Christophe, Nonat, Andre, 2007, The Cement Cohesion: An Affair of
Electrostatics, Lutam Symposium on Swelling and Shrinkage of Porous Materials, Petropolis,
Brazil
61
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Wet Stage Properties of Tec-Cement Concretes
• Water has cohesivity due to a network of extensive three-dimensional
hydrogen bonding and this property is strengthened both by Brucite surfaces
and the strongly kosmotropic Mg++ ion and other species in solution.
• The strong polar bonding
– Affects all wet stage properties
•
•
•
•
•
•
Improving rheology markedly (all formulations)
Reducing early age shrinkage
Contributing to dissolution of clinker, gbfs etc.
Contributing to high early strength
Reducing bleed water thereby retaining alkali
Making the mixes highly thixotropic
– Significantly brings forward the onset of
first set with high replacement mixes.
• Increases the “wet sand effect” effect.
• MgO goes negative
– Helps deliver high early strength
62
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+
O
+
+
O
-
+
+
O +
O
O - +
O
+
+
O
-
+
+
+
++
-
Mg
-
-
O
+
+
+
+
Ca++ = 114 picometres
Mg++ = 86 picometres
Dissolution – By Proton Wrenching?
According to Pellenq from MIT water dissociates
and the protons formed move in a Grotthus like
way (i.e. by proton hopping) penetrating the
crystal structure of alite and play a role in
breaking it apart. Belite has a different crystal
structure and this does not occur to the same
extent. Pellenq suggests change Belite structure
using aluminium. We mention that aluminium
works in our patents at length so have the prior
art however Pellenq et. al. add understanding as
to possibly why. We suggest changing the
nature of water by adding Mg++. (See later, note
both methods work well together)
Dissolution of alite by proton wrenching
6
Image Source: Slide in a presentation by Prof Roland
Pellenq, MIT Concrete Sustainability Hub
63
Magnesium is mainly present as Mg2+ (aq.) in
water, but also as MgOH+ (aq.) and Mg(OH)2
(aq.) and other species. The strong electron pull
of magnesium may also play a role in dissolution
as we have noticed a much faster early setting
rate and can make cements with pure gbfs for
example. i.e Mg++ and associated aqueous
species probably play a role in dissolution
processes.
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The Effect of a
Strong Kosmotrope such as Mg++
--
Polar covalent bonds
O--
-H+
++
O--
H+
H+
Polar covalent bonds
Mg++
Polar bond --
++
O--
H+
-Mg++
O--
H+
Polar bond
This propagates and may cause more rapid dissolution of
clinker, GBFS and other hydraulic cements leading to
H+ earlier more complete reaction and thus early strength.
These drawings are subject to copyright by TecEco
64
The charge
distribution on water
is strongly influenced
by the presence of a
kosmotropic cation
such as Mg++ which
has a strong polar
bonding affinity for
the oxygen end of
water.
www.tececo.com
Setting – An Electrostatic Affair?
The Wet Beach affect
Sand is largely silica that has
broken into small grains. At the
atomic scale, silica
consists of a three-dimensional
network of covalently bonded
silicon and oxygen atoms.
Typically, silica surfaces contain
mostly oxygen atoms, many of
which are covalently bonded to
hydrogen atoms.
The surface contains many polar
bonds and can hydrogen-bond to
water molecules. Therefore water
is attracted to silica
surfaces, which are said to be
hydrophilic (water loving).
65
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MgO has a Bar Magnet Effect
The Change in the Surface Charge of Metal Oxides with pH.
7Source:Small,
R.J. et al., 2005. Using a buffered rinse solution to minimize metal contamination after wafer
cleaning. MicroMagazine.com. Available at: http://www.micromagazine.com/archive/98/01/small.html.
66
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High and Total Replacement Cements
• TecEco recently announced a way forward to greater
sustainability for the Portland cement industry.
• Up to 30% or more strength at all stages with high & very high
replacement ternary mixes. (GBFS +- fly ash replacing PC.)
• Total replacement with class C fly ash and gbfs is possible
• Finishers can go home early using >50% replacement mixes
removing the remaining barrier to their implementation.
• Brilliant rheology, low shrinkage and little or no cracking.
• Excellent durability.
• A solution to autogenous shrinkage?
• Mixes with MgO can tolerate carbon in fly ash and clays to some
extent.
• Mg++ combines with chloride or sulphate immobilising these cations
67
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Example Results for TecEco
Date of Trial Mix
Constituents
GP PC, kg/m3
Fly ash, kg/m3
Slag, kg/m3
Reactive Magnesia, kg/m3
MgO relative to PC
Kg
116
58
58
10
20mm, kg/m3
10mm, kg/m3
Total Coarse Aggregate
710
275
985
Manufactured Sand, kg/m3
Fine Sand, kg/m3
Total Fine Aggregate
3/12/2010
32MPa
%
47.93
23.97
23.97
4.13
8.7
Kg
155
78
78
13.4
%
47.78
24.04
24.04
4.13
8.7
50.0
45.0
40.0
35.0
30.0
25.0
20 Mpa
730
280
1010
20.0
32MPa
490
390
880
440
350
790
5.0
WR (WRDA PN), ml/100kg
350
400
Water, lt/m3
185
199
Design Slump, mm
Actual Slump, mm
80
80
100
100
20 MPa
13.0
18.0
32.5
39.0
32MPa
17.0
24.5
42.5
46.5
20 MPa
330
430
500
560
660
32MPa
320
420
490
520
580
Strength
3 Day
NB. Our patents in all
7 Day
28 Day countries define the
56 Day minimum added %
MgO as being >5% of
Shrinkagehydraulic cement
1 week
components or
2 week
3 week hydraulic cement
4 week components + MgO
7 week
68
30/10/2010
20MPa
15.0
10.0
0.0
3 Day
7 Day
28 Day
56 Day
700
600
500
400
20 Mpa
300
32MPa
200
100
0
1 week 2 week 3 week 4 week 5 week 6 week 7 week
www.tececo.com
A Tec-Cement Modified Ternary Mix
69
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Tec-Cement Mixes
70
Ordinary Mixes
TecEco Tec-Cement Mixes
Notes
Reactive MgO as defined
None
Usually 8 to 10% / PC added
1
Pozzolan
Should be used
Recommended.
Supplementary cementitious
materials (SCM’s)
Should be used
Recommended.
Limit on additions pozzolans +
SCM’s
Limited by standards that are
increasingly exceeded
> 50% recommended especially
if a ternary blend
Rheology
Usually sticky, especially with fly
ash. Hard to finish.
Slippery and creamy. Easy to
finish.
Setting time
Slow. Especially with fly ash only.
Much faster. Blends with a high
proportion Pos. and SCM’s set
like ordinary PC concrete.
Shrinkage and cracking
Significant
Much less
Additives
Usually used
Not necessary
Durability
Without additions of Pozzolans and
SCM’s questionable.
Excellent especially with
additions of Pozzolans and SCM’s
28 day Strength (20 MPA mix)
< .20 MPa/Kg PC/m3
> .27 MPa/Kg PC/m3
$ Cost Binder/MPa at 28 days
(20 & 32 MPa mixes)
> ($2.30-$2.50)
< ($1.50-$1.90)
We recommend
using both
Pozzolans and
SCM’s together 2
Notes
1. See http://www.tececo.com/technical.reactive_magnesia.php. % is relative to PC and in addition to amount already in PC
2. To keep our patents simple we included supplementary cementitious materials as pozzolans in our specification
3. See economics pages following
3
Why Put Brucite in Concretes?
• Improved rheology (see
http://www.tececo.com/technical.rheologica
l_shrinkage.php)
• Prevents shrinkage and cracking (see
http://www.tececo.com/technical.rheologica
l_shrinkage.php)
• Provides low shrinkage and pH and eH
control. Reduced corrosion. Stabilises CSH
when Ca++ consumed by the pozzolanic
reaction (Encouraged)
• Relinquishes polar bound water for more
complete hydration of PC thereby preventing
autogenous shrinkage?
• Solves the carbon in fly ash, sulfate,
chloride and clay in aggregate problems.
71
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Equilibrium
pH brucite
Pourbaix diagram steel reinforcing
Durability (Important for Sustainability)
• Durability is related to
– How easy is it for an aggressive agent to get into the concrete matrix
• This depends on the density which depends on the voids and specific gravity
of the minerals present.
– The number and size of voids depends on the particle packing and water added.
– If the number and size of voids causes percolation points to be exceeded then the
material is permeable and thus not likely to be durable depending on the Eh-pH
– Strength is not the cause of strength but a bad proxy for permeability.
– What the aggressive agent can do once in there
• Depends on the Eh-pH conditions inside the matrix
– Ideally reducing Eh and pH above about 9.5 depending on the Eh.
– Brucite the hydration product of reactive MgO stabilises the pH in
concrete. The equilibrium pH of Brucite is around 10.42.
– Reactive MgO will also remove chloride and sulfate by reacting with
them.
Durability is badly understood. Many text books
– The electro coupling present
• e.g. steel – chloride
72
get their chemistry 101 facts incorrect especially
in relation to rheo bar .
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Dry Stage Properties of
Tec-Cement Concretes
• Significantly increased tensile strength
• Increased compressive strength (especially early strength) particularly with
high replacement mixes containing significant amounts of GBFS compacting
factor
• Reduced shrinkage and cracking
• Improved durability
• Higher tensile strain capacity?
• Greater creep
• Less permeable?
• Lighter albido
• Solves autogenous shrinkage problems
• May solve other delayed reaction problems
8Recommended
Reading: Du C. A Review of Magnesium Oxide in
Concrete - A serendipitous discovery leads to new concrete for dam
construction. Concrete International. 2005;(December 2005):45 - 50.
73
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Solving Autogenous
Shrinkage to Reduce Emissions
In most concrete 18-23% of the PC used never hydrates. If all the PC used
could be made to hydrate less could be used saving on emissions be around 20%.
2C3S+7H => C3S2H4 + 3CH
2C2S+5H => C3S2H4 + CH
Brucite
consists of
polar
bound
layers of
ionically
bound
atoms
Brucite
hydrates
consist
of polar
bound
layers of
ionically
bound
atoms
NB. We think this loosely
bound polar water is
available for the more
complete hydration of PC.
74
Strongly differentially charged surfaces
and polar bound water account for many
of the properties of brucite
www.tececo.com
Economics of Tec-Cements
126
Normal 20 Mpa
Mpa/Kg PC/m3
Kg PC/Mpa/m3
$/Mpa, 20 Mpa mix
116
Days => 3 Day
Kg PC
9.1
0.072222
13.85
6.23
Kg PC
7 Day
28 Day
56 Day
12.6
0.1
10.00
4.50
22.75
0.180556
5.54
2.49
27.3
0.216667
4.62
2.08
Binder Prices Only
$/Mpa, 20 Mpa mixes
7.00
6.00
5.00
13.0
Mpa/Kg PC/m3
0.112069 0.155172 0.280172 0.336207
3.00
8.92
6.44
3.57
2.97
2.00
4.25
3.07
1.70
1.42
1.00
Kg PC/Mpa/m
3
$/Mpa, 20 Mpa Tec-Cement mix
168.4
18.0
32.5
39.0
11.9
17.15
29.75
Mpa/Kg PC/m
0.070665 0.101841 0.176663 0.19329
Kg PC/Mpa/m
3
14.15
9.82
5.66
5.17
$/Mpa, 32 Mpa mix
6.37
4.42
2.55
2.33
155
Kg PC
TecEco 32 MPa
Mpa/Kg PC/m3
Kg PC/Mpa/m3
$/Mpa, 32 Mpa Tec-Cement mix
17.0
0.109677
9.12
4.34
24.5
0.158065
6.33
3.01
42.5
0.274194
3.65
1.74
46.5
0.3
3.33
1.59
Relative Strength Factor
Price PC
% PC (PC + MgO)
Price MgO
% MgO (PC + MgO)
70%
0.45
91.30%
0.75
8.70%
Mix with no added MgO
Kg
%
Kg
%
$
3 Day
32.55
3
$
$/Mpa, 20 Mpa TecCement mix
0.00
Kg PC
Normal 32 Mpa
$/Mpa, 20 Mpa mix
4.00
TecEco 20 Mpa
7 Day
28 Day
56 Day
$/Mpa, 32 Mpa mixes
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
$/Mpa, 32 Mpa mix
$/Mpa, 32 Mpa TecCement mix
3 Day
7 Day
28 Day
56 Day
This embedded spread sheet looks only at the binder price and assumes all other factors
remain the same
75
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Agglomeration of
Carbonates, Fly ash and other Wastes
• Sand and stone aggregate are in short supply in some areas.
• Nesquehonite is an ideal micro aggregate so why not
agglomerate it and/or other magnesium carbonates to make man
made manufactured aggregate?
• MgO binders will be suitable for this purpose and TecEco are
seeking funding to demonstrate the technology.
• TecEco can already agglomerate fly ash and nesquehonite
without additional energy. We just can’t tell you how as we have
not had the money to pursue a patent.
76
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Man Made Carbonate
Aggregate?
Tonnes 20,000,000,000
18,000,000,000
16,000,000,000
World Production PC
With carbon trading think of
the potential for
sequestration (=money with
carbon credits) making man
made carbonate aggregate
14,000,000,000
12,000,000,000
10,000,000,000
Tonnes CO2 from unmodified PC
World Production Concrete
8,000,000,000
Calculated Proportion Aggregate
6,000,000,000
4,000,000,000
CO2 Sequestered in Mg Carbonate
Aggregate
2,000,000,000
Net Sequestration
2009
2006
2003
2000
1997
1994
1991
1988
1985
1982
1979
1976
1973
1970
1967
1964
1961
1958
1955
1952
1949
1946
0
Assumptions - 50% non PC N-Mg mix and Substitution by Mg Carbonate Aggregate
Percentage by Weight of Cement in Concrete
Percentage by weight of MgO in cement
Percentage by weight CaO in cement
Proportion Cement Fly ash and/or GBFS
1 tonne Portland Cement
Proportion Concrete that is Aggregate
CO2 captured in 1 tonne aggregate
77
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Source USGS: Cement Pages
15.00%
6%
29%
50%
0.867Tonnes CO2
85%
1.092Tonnes CO2
A final Note re TecEco Technology
In this presentation we have given you so some insights into why reactive
MgO is the most powerful new tool in cement chemistry.
The ramifications of the effect of the Mg++ ion on water chemistry will
go beyond hydraulic cements but we are a small company and do not
have the money to patent other applications we are aware of.
In relation to hydraulic cements including by definition gbfs in some of
our applications we would appreciate that you honour our intellectual
property.
For the good of all we are working now to produce reactive MgO cheaply
from brines rich in Mg++ such as oil and gas or de-sal process water.
If you are interested further please contact us.
78
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