Transcript Slide 1

Implementing Sustainability
TecEco are in the
biggest business
on the planet –
that of solving
global warming
waste and water
problems
Presentation by John
Harrison, managing director
of TecEco and inventor of
Tec and Eco-Cements and
the CarbonSafe process.
Our slides are deliberately verbose as most people download
and view them from the net. Because of time constraints I will
have to race over some slides
John Harrison B.Sc. B.Ec. FCPA.
Presentation downloadable from www.tececo.com
1
The Problem. We have a Planet in Crisis
 In the next 50 years it is crunch time for:
– Fresh Water
– Global
warming
– Energy
– Waste &
Pollution
 Are you thinking about it? Do you have an
answer?
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2
Fresh Water
 The amount of water in the world is finite.
The number of us is growing quickly and our
water use is growing more quickly.
 A third of the world's population lives in
water-stressed countries. By 2025, this is
expected to rise to two-thirds.
 The world's supply of fresh water is running
out. Already one person in five has no
access to safe drinking water.
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3
Global Warming
Rises in the levels
of carbon dioxide
and other gases
(methane, water
vapour)
Are causing a rapid
rise in temperature
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4
The Carbon Cycle and Emissions
Emissions
from fossil
fuels and
cement
production
are the
cause of the
global
warming
problem
Source: David Schimel and Lisa Dilling, National Centre for Atmospheric Research 2003
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5
Energy Crisis
Peak Oil Production (Campell 2004)
Most models of oil reserves, production and consumption show peak oil around
2010 (Campbell 2005) and serious undersupply and rapidly escalating prices by
2025. It follows that there will be economic mayhem unless the cement and
concrete industry acts now to change the energy base of their products.
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6
Waste & Pollution
Waste releases methane, can
cause ill health in the area, leads to
the contamination of land,
underground water, streams and
coastal waters (destroying our
fisheries) and gives rise to various
nuisances including increased
traffic, noise, odours, smoke, dust,
litter and pests.
Most damaging is the release of
dangerous molecules to the global
commons
There are various estimates, but we produce about 5-600
million tonnes of waste each year.
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Ecological Footprint
Our footprint is exceeding the capacity of the planet to
support it. We are not longer sustainable as a species and
must change our ways TO SURVIVE
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All these Problems Represent an Opportunity to Do
Something About Them
 The built environment is made of materials and is
our footprint on earth.
– It comprises buildings and infrastructure.
 Construction materials comprise
– 70% of materials flows (buildings, infrastructure etc.)
– 40-50% of waste that goes to landfill (15 % of new materials
going to site are wasted.)
 Over 30 billion tonnes of building materials are
used annually on a world wide basis.
– Mostly using virgin natural resources
– Combined in such a manner they cannot easily be separated.
– And include many toxic elements.
 The single biggest materials flow (after water) is
concrete at around 15 billion tonnes or > 2 tonnes per
man, woman and child on the planet.
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9
How? - The Techno-Processes & Earth Systems
Underlying
the technoEarth Systems
process that
describes and
Atmospheric
Detrimental
controls the
composition,
affects
on
flow of matter
climate, land
Waste
and energy
earth
cover, marine
are molecular
systems
ecosystems,
stocks and
Take
pollution,
flows. If out of
coastal zones,
tune with
freshwater and
nature these
moleconomic
salinity.
flows have
detrimental
affects on
earth
To reduce the impact on earth systems new technical paradigms
systems.
need to be invented that result in underlying molecular flows that
mimic or at least do not interfere with natural flows.
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Under Materials Flows in the Techno-Processes are Molecular Flows
Take → Manipulate → Make → Use → Waste
[
[
←Materials→
]
← Underlying molecular flow → ]
If the underlying molecular flows are “out of tune” with
nature there is damage to the environment
e.g. heavy metals, cfc’s, c=halogen compounds and CO2
Moleconomics
Is the study of the form of atoms in molecules, their flow, interactions,
balances, stocks and positions. What we take from the environment
around us, how we manipulate and make materials out of what we take
and what we waste result in underlying molecular flows that affect earth
systems. These flows should mimic or minimally interfere with natural
flows.
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There are Detrimental Affects Right
Through the Techno-process
Detrimental
Linkages that
affect earth
system flows
Take
manipulate
and make
impacts
Materials are
End of
in the
lifecycle
Technoimpacts
sphere Utility
zone
Materials are everything between the take
There
is no
such
place
as
“away”
and waste and affect earth system flows.
Greater Utility
Less Utility
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We Must Learn from Nature (Biomimicry)
 Nature is very efficient. The waste from one plant or animal is
the food or home for another.
 By studying Nature we learn who we are, what we are and
how we are to be.” (Wright, F.L. 1957:269)
 In nature photosynthesis balances respiration.
 We have nothing that balances our emissions in the technoprocess
 There is a strong need for similar efficiency and balance
By learning from
Nature we can all
live together
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Biomimicry
 The term biomimicry was popularised by the book of
the same name written by Janine Benyus
 Biomimicry is a method of solving problems that uses
natural processes and systems as a source of
knowledge and inspiration.
 It involves nature as model, measure and mentor.
The theory behind biomimicry is that natural processes
and systems have evolved over several billion years
through a process of research and development
commonly referred to as evolution. A reoccurring theme
in natural systems is the cyclical flow of matter in such a
way that there is no waste of matter or energy.
Nature is very economical about all Processes.
We must also be MUCH more economical
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Economically Driven Sustainability
$ - ECONOMICS - $
The challenge is to harness human
behaviours which underlay economic
supply and demand phenomena by
changing the technical paradigm in
favour of making carbon dioxide and
other wastes resources for new
materials with lower take and waste
impacts and more energy efficient
performance.
Sustainable processes are more efficient and therefore more
economic. Natural ecosystems can be 100% efficient. What is needed
are new technologies that allow material and energy flows to more
closely mimic natural ecosystems.
Innovation will deliver these new technical paradigms.
Sustainability will not happen by relying
on people to do the right thing
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Sustainability = Culture + Technology
Increase in demand/price ratio for
sustainability due to educationally
induced cultural drift.
$
ECONOMICS
New Technical
Paradigms are
required that deliver
sustainability.
Equilibrium shift
Supply
Greater Value/for
impact
(Sustainability) and
economic growth
Increase in supply/price ratio for
more sustainable products due to
innovative paradigm shifts in
technology.
Demand
#
One aspect of sustainability is that it is
where Culture and Technology meet.
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Changing the Technology Paradigm
We need materials that require less energy to
make them, that last much longer and that
contribute properties that reduce lifetime energies.
The key is to change the technology paradigm
“By enabling us to make productive use of
particular raw materials, technology
determines what constitutes a physical
resource1”
1.Pilzer, Paul Zane, Unlimited Wealth, The Theory and Practice of
Economic Alchemy, Crown Publishers Inc. New York.1990
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Examples of Economic Changes in Technical
Paradigms that result in Greater Sustainability
Incandescent
100 watts
1700 lumens
Fluorescent
Led Light
<20 watts
25 watts
1700 lumens 1700 lumens
Light Globes - A Recent Paradigm Shift
in Technology Reducing Energy
Consumption
Light Globes in the last 10 years have evolved
from consuming around 100 watts per 1700
lumens to less that 20 watts per 1700 lumens.
As light globes account for around 30% of
household energy this is as considerable saving.
Robotics - A Paradigm Shift in Technology
that will fundamentally affect Building and
Construction
Construction in the future will be largely done by
robots because it will be more economic to do so.
Like a color printer different materials will be
required for different parts of structures, and wastes
such as plastics will provide many of the properties
required for the cementitious composites of the
future used. A non-reactive binder such as TecEco
tec-cements can supply the right rheology, and like
a printer, very little will be wasted.
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The TecEco CarbonSafe Industrial Ecology
Inputs
Brines
Waste Acid
CO2
Outputs
Gypsum, Sodium
bicarbonate, Salts,
Building materials,
Potable water
We must design whole new technical
paradigms that reverse many of our
problem molecular flows
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A Low Energy Post – Carbon & Waste Age?
The construction
industry can be
uniquely responsible
for helping achieve this
transition
Maybe then we can move
confidently into a more
sustainable future.
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Innovative New Materials - the Key to Sustainability
The choice of materials controls emissions, lifetime and embodied
energies, user comfort, use of recycled wastes, durability, recyclability
and the properties of wastes returned to the bio-geo-sphere.
There is no such place as “away”, only a global commons
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Re - Engineering Materials – What we Build With
Environmental
problems are
the result of
inherently
flawed
materials,
materials flows
and energy
systems
 To solve environmental problems
we need to understand more
about materials in relation to the
environment.
– the way their precursors are derived and
their degradation products re assimilated
• and how we can reduce the impact of
these processes
– what energies drive the evolution,
devolution and flow of materials
• and how we can reduce these energies
– how materials impact on lifetime energies
 With the knowledge gained redesign materials to not only be
more sustainable but more
sustainable in use
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Changing the Techno-process
Take => manipulate => make => use => waste
Driven by fossil fuel energy with detrimental effects on earth systems.
Reduce
Re-use
Recycle
Reduce
Take only
renewables
Manipulate
Make
Eco-innovate
Reuse
Use
Waste only what is
biodegradable or can
be re-assimilated
Recycle
Materials
Improving the sustainability of materials used to create the built environment
will reduce the impact of the take and waste phases of the techno-process
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Huge Potential for Sustainable Materials
Reducing the impact of the take and
waste phases of the techno-process.
– including carbon in materials
they are potentially carbon sinks.
– including wastes for
physical properties as
well as chemical composition
C
they become resources.
– re – engineering
Waste
materials to
reduce the lifetime
energy of buildings C
Many wastes can
contribute to
physical
properties
reducing lifetime
energies
C
C
Waste
C
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Utilizing Carbon and Wastes (Biomimicry)
 During earth's geological history large tonnages of
carbon were put away as limestone and other
carbonates and as coal and petroleum by the activity of
plants and animals.
 Sequestering carbon in magnesium binders and
aggregates in the built environment mimics nature in that
carbon is used in the homes or skeletal structures of
most plants and animals.
We all use carbon and wastes to
make our homes! “Biomimicry”
In eco-cement blocks
and mortars the
binder is carbonate
and the aggregates
are preferably wastes
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Impact of the Largest Material Flow - Cement and Concrete
 Concrete made with cement is the most widely
used material on Earth accounting for some
30% of all materials flows on the planet and 70%
of all materials flows in the built environment.
– Global Portland cement production is currently in the
order of 2 billion tonnes per annum.
– Globally over 14 billion tonnes of concrete are poured
per year.
– Over 2 tonnes per person per annum
– Much more concrete is used than any other building
material.
TecEco Pty. Ltd. have benchmark technologies for
improvement in sustainability and properties
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Embodied Energy of Building Materials
Concrete is
relatively
environmentally
friendly and 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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Average Embodied Energy in Buildings
Most of the embodied energy in the
built environment is in concrete.
Because so much concrete is used there is a
huge opportunity for sustainability by reducing
the embodied energy, reducing the carbon
debt (net emissions) and improving properties
that reduce lifetime energies.
Downloaded from www.dbce.csiro.au/indserv/brochures/embodied/embodied.htm (last accessed 07 March 2000)
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Emissions from Cement Production
 Chemical Release
– The process of calcination involves driving off chemically bound
CO2 with heat.
CaCO3 →CaO + ↑CO2
CO2
 Process Energy
– Most energy is derived from fossil fuels.
CO2
– Fuel oil, coal and natural gas are directly or indirectly burned to
produce the energy required releasing CO2.
 The production of cement for concretes accounts for around
10% of global anthropogenic CO2.
– Pearce, F., "The Concrete Jungle Overheats", New Scientist, 19 July,
No 2097, 1997 (page 14).
Arguments that we should reduce cement production relative to other
building materials are nonsense because concrete is the most sustainable
building material there is. The challenge is to make it more sustainable.
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Cement Production ~= Carbon Dioxide Emissions
Metric Tonnes
2,500,000,000
2,000,000,000
1,500,000,000
1,000,000,000
500,000,000
2001
1996
1991
1986
1981
1976
1971
1966
1961
1956
1951
1946
1941
1936
1931
1926
0
Year
Between tec, eco and enviro-cements TecEco can provide a
viable much more sustainable alternative.
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TecEco Technologies Take Concrete into the Future
 More rapid strength gain even with added
pozzolans
– More supplementary materials can be used reducing
costs and take and waste impacts.
 Higher strength/binder ratio
 Less cement can be used reducing costs and
take and waste impacts
 More durable concretes
Tec Cements
– Reducing costs and take and waste impacts.
 Use of wastes
 Utilizing carbon dioxide
Tec & EcoEco-Cements Cements
 Magnesia component can be made using non
fossil fuel energy and CO2 captured during
production.
Presentation downloadable from www.tececo.com
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TecEco Binder Systems
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
STRENGTH
TecEco concretes are
a system of blending
REACTIVE MAGNESIA
reactive magnesia,
Hydration of magnesia => brucite for strength, workability, Portland cement and
dimensional stability and durability. In Eco-cements
usually a pozzolan
carbonation of brucite => nesquehonite, lansfordite and
with other materials
an amorphous phase for sustainability.
and are a key factor
for sustainability.
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32
TecEco Formulations
 Tec-cements (5-15% MgO, 85-95% OPC)
– contain more Portland cement than reactive magnesia. Reactive magnesia
hydrates in the same rate order as Portland cement forming Brucite which uses
up 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 many of
which are potentially wastes without reaction problems.
 Eco-cements (15-95% MgO, 85-5% OPC)
– contain more reactive magnesia than in tec-cements. Brucite in porous
materials carbonates forming stronger fibrous mineral carbonates and therefore
presenting huge opportunities for waste utilisation and sequestration.
 Enviro-cements (5-15% MgO, 85-95% OPC)
– contain similar ratios of MgO and OPC to eco-cements but in non porous
concretes brucite does not carbonate readily.
– Higher proportions of magnesia are most suited to toxic and hazardous waste
immobilisation and when durability is required. Strength is not developed
quickly nor to the same extent.
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33
Tec & Eco-Cement Theory
 Many Engineering Issues are Actually
Mineralogical Issues
– Problems with Portland cement concretes are usually resolved
by the “band aid” engineering fixes. 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.
– Portlandite and water are the weakness of concrete
• TecEco remove Portlandite it and replacing it with magnesia which
hydrates to Brucite.
• The hydration of magnesia consumes significant water
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Tec & Eco-Cement Theory
 Portlandite (Ca(OH)2) is too soluble, mobile and reactive.
– It carbonates, reacts with Cl- and SO4- and being soluble can act
as an electrolyte.
 TecEco generally (but not always) remove Portlandite using
the pozzolanic reaction and
 TecEco add reactive magnesia
– which hydrates, consuming significant water and concentrating
alkalis forming Brucite which is another alkali, but much less
soluble, mobile or reactive than Portlandite.
 In Eco-Cements brucite carbonates forming
hydrated compounds with greater volume
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Why Add Reactive Magnesia?
 To maintain the long term stability of CSH.
– Maintains alkalinity preventing the reduction in Ca/Si ratio.
 To remove water.
– Reactive magnesia consumes water as it hydrates to possibly
hydrated forms of Brucite.
 To raise the early Ph.
– Increasing non hydraulic strength giving reactions
 To reduce shrinkage.
– The consequences of putting brucite through the matrix of a concrete
in the first place need to be considered.
 To make concretes more durable
 Because significant quantities of carbonates are produced
in porous substrates which are affective binders.
Reactive MgO is a new tool to be understood
with profound affects on most properties
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Strength with Blend & Porosity
150
Tec-cement concretes
100
Eco-cement concretes
50
High OPC
Enviro-cement
concretes
STRENGTH ON
ARBITARY SCALE 1-100
100-150
50-100
0-50
0 High Porosity
High Magnesia
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TecEco Technology in Practice
=> Whittlesea, Vic. Australia
On 17th March 2005 TecEco poured the
first commercial slab in the world using
tec-cement concrete with the
assistance of one of the larger cement
and pre-mix companies.
–
–
–
The formulation strategy was to adjust a
standard 20 MPa high fly ash (36%) mix
from the company as a basis of
comparison.
Strength development, and in particular
early strength development was good.
Interestingly some 70 days later the slab is
still gaining strength at the rate of about 5
MPa a month.
Also noticeable was the fact that the
concrete was not as "sticky" as it normally
is with a fly ash mix and that it did not
bleed quite as much.
Shrinkage was low. 7 days - 133 micro
strains, 14 days - 240 micro strains, 28
days - 316 micros strains and at 56 days 470 microstrains.
Strength Development of Tec-Cement Concrete
30
Strength, MPa
–
25
20
Compressive
Strength
15
10
5
0
0
5
10
15
20
25
30
Days w ater cured
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TecEco Technology in Practice
=> Porous Pavement
Allow many mega
litres of good fresh
water to become
contaminated by the
pollutants on our
streets and pollute
coastal waterways
Or
Capture and cleanse
the water for our use?
Presentation downloadable from www.tececo.com
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TecEco Technology in Practice
=> Whittlesea, Vic. Australia
First Eco-cement mud
bricks and mortars in
Australia
– Tested up twice as strong as
the PC controls
– Mud brick addition rate 2.5%
– Addition rate for mortars 1:8
not 1:3 because of molar
ratio volume increase with
MgO compared to lime.
Presentation downloadable from www.tececo.com
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TecEco Technology in Practice
=> Earthship Brighton, UK
By Taus Larsen, (Architect, Low Carbon Network Ltd.)
The Low Carbon Network (www.lowcarbon.co.uk) was established to raise awareness of the links between
buildings, the working and living patterns they create, and global warming and aims to initiate change
through the application of innovative ideas and approaches to construction. England’s first Earthship is
currently under construction in southern England outside Brighton at Stanmer Park and TecEco
technologies have been used for the floors and some walling.
Earthships are exemplars of low-carbon design, construction and living and were invented and developed in the USA
by Mike Reynolds over 20 years of practical building exploration. They are autonomous earth-sheltered buildings
independent from mains electricity, water and waste systems and have little or no utility costs.
For information about the Earthship Brighton and other projects please go to the TecEco web site.
Presentation downloadable from www.tececo.com
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TecEco Technology in Practice
=> Clifton Surf Life Saving Club
The Clifton Surf Life Saving Club was built by first
pouring footings, On the footings block walls were
erected and then at a later date concrete was laid in
between.
As the ground underneath the footings was sandy, wet
most of the time and full of salts it was a recipe for
disaster.
Predictably the salty water rose up through the footings
and then through the blocks and where the water
evaporated there was strong efflorescence, pitting, loss
of material and damage.
The TecEco solution was to make up a
formulation of eco-cement mortar which we
doctored with some special chemicals to prevent
the rise of any more moisture and salt.
The solution worked well and appears to have
stopped the problem.
Presentation downloadable from www.tececo.com
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TecEco Technology in Practice
=> Mike Burdon’s Murdunna Works
Mike Burdon, Builder and Plumber.
I work for a council interested in sutainability and
have been involved with TecEco since around
2001 in a private capacity helping with large
scale testing of TecEco tec-cements at our
shack.
I am interested in the potentially superior
strength development and sustainability aspects.
To date we have poured two slabs, footings, part
of a launching ramp and some tilt up panels
using formulations and materials supplied by
John Harrison of TecEco. I believe that research
into the new TecEco cements essential as
overall I have found:
1.
The rheological performance even without plasticizer was excellent. As testimony to this the contractors on the site
commented on how easy the concrete was to place and finish.
2.
We tested the TecEco formulations with a hired concrete pump and found it extremely easy to pump and place. Once in
position it appeared to “gel up” quickly allowing stepping for a foundation to a brick wall.
3.
Strength gain was more rapid than with Portland cement controls from the same premix plant and continued for longer.
4.
The surfaces of the concrete appeared to be particularly hard and I put this down to the fact that much less bleeding was
observed than would be expected with a Portland cement only formulation
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43
TecEco Technology in Practice
=> DJ Motors, Hobart
Tec-Cement
concretes exhibit little
or no shrinkage. At
10% substitution of
MgO for PC the
shrinkage is less than
half normal. At 18%
substitution with no
added pozzolan there
was no measurable
shrinkage or
expansion.
The above photo shows a tec-cement concrete topping coat (with no flyash)
20mm thick away from the door and 80 mm thick near the door. Note that
there has been no tendency to push the tiles or shrink away from the borders
as would normally be the case.
Presentation downloadable from www.tececo.com
44
TecEco Technology in Practice
=> Island Block and Paver,Tasmania
TecEco Tec and EcoCement blocks are now
being made
commercially in
Tasmania and with
freight equalization may
be viable to ship to
Victoria for your “green”
project. Hopefully soon
we will have a premix
mortar available that
uses eco-cement.
Presentation downloadable from www.tececo.com
45
TecEco Technology in Practice
=> Foamed Concretes
BUILD LITE CELLULAR CONCRETE
4 Rosebank Ave Clayton Sth
MELBOURNE AUSTRALIA 3169
PH 61 3 9547 0255 FX 61 3 9547 0266
Foamed TecEco cement concretes
can be produced to about 30%
weight reduction in concrete trucks
using cellflow additive or to about
70% weight reduction using a
foaming machine with mearlcrete
additive (or equivalents)
Presentation downloadable from www.tececo.com
46
Tec & Eco Cement Foamed Concrete Slabs
=> Foamed Concrete Slabs
BUILD LITE CELLULAR CONCRETE
4 Rosebank Ave Clayton Sth
MELBOURNE AUSTRALIA 3169
PH 61 3 9547 0255 FX 61 3 9547 0266
Presentation downloadable from www.tececo.com
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TecEco Technology in Practice
=> Foamed Concretes Panels
Imagine a conventional steel frame section
with a foamed concrete panel built in adding
to structural strength, providing insulation as
well as the external cladding of a structure.
Solutions in Steel
ABN 48 103 573 039
TEL: 61 7 3271 3900
FAX: 61 7 3271 2701
80 Mica Street
Carole Park 4300
Queensland
Australia
Rigid Steel Framing have developed just such
a panel and have chosen to use TecEco
cement technology for the strength, ease of
use and finish.
Patents applied for by Rigid Steel Framing
Please direct commercial enquiries to
Rigid Steel Framing at rigidsteel.com.au
Presentation downloadable from www.tececo.com
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TecEco Technology in Practice
=> Foamed Concretes Panels
Rear view of test panels showing tongue and groove and void for services.
Interior plasterboard is fixed conventionally over gap for services.
Presentation downloadable from www.tececo.com
49
Eco-Cements
 Eco-cements are similar but potentially superior to lime mortars
because:
– The calcination phase of the magnesium thermodynamic cycle takes
place at a much lower temperature and is therefore more efficient.
– Magnesium minerals are generally more fibrous and acicular than calcium
minerals and hence add microstructural strength.
 Water forms part of the binder minerals that forming making the
cement component go further. In terms of binder produced for
starting material in cement, eco-cements are much more
efficient.
 Magnesium hydroxide in particular and to some extent the
carbonates are less reactive and mobile and thus much more
durable.
Presentation downloadable from www.tececo.com
50
Eco-Cements
 Have high proportions of reactive magnesium oxide
 Carbonate like lime
 Generally used in a 1:5-1:12 paste basis because much more
carbonate “binder” is produced than with lime
MgO + H2O <=> Mg(OH)2
Mostly CO2
and water
Mg(OH)2 + CO2 + H2O <=> MgCO3.3H2O
58.31 + 44.01 <=> 138.32 molar mass (at least!)
24.29 + gas <=> 74.77 molar volumes (at least!)
 307 % expansion (less water volume reduction) producing much
more binder per mole of MgO than lime (around 8 times)
 Carbonates tend to be fibrous adding significant micro
structural strength compared to lime
As Fred Pearce reported in New Scientist Magazine
(Pearce, F., 2002), “There is a way to make our city
streets as green as the Amazon rainforest”.
Presentation downloadable from www.tececo.com
51
CO2 Abatement in Eco-Cements
For 85 wt%
Aggregates
15 wt%
Cement
Eco-cements in
porous products
absorb carbon
dioxide from the
atmosphere.
Brucite carbonates
forming lansfordite,
nesquehonite and
an amorphous
phase, completing
the thermodynamic
cycle.
Portland
Cements
15 mass%
Portland
cement, 85
mass%
aggregate
Emissions
.32 tonnes to
the tonne.
After
carbonation.
Approximately
.299 tonne to
the tonne.
No
Capture
11.25% mass%
reactive
magnesia, 3.75
mass% Portland
cement, 85
mass%
aggregate.
Emissions
.37 tonnes to
the tonne. After
carbonation.
approximately
.241 tonne to
the tonne.
Capture
CO2
11.25% mass%
reactive
magnesia, 3.75
mass% Portland
cement, 85
mass%
aggregate.
Emissions
.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 eco-cement, 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.
Presentation downloadable from www.tececo.com
52
Eco-Cement Strength Development
 Eco-cements gain early strength from the hydration of
PC.
 Later strength comes from the carbonation of brucite
forming an amorphous phase, lansfordite and
nesquehonite.
 Strength gain in eco-cements is mainly microstructural
because of
– More ideal particle packing (Brucite particles at 4-5 micron are
under half the size of cement grains.)
– The natural fibrous and acicular shape of magnesium carbonate
minerals which tend to lock together.
 More binder is formed than with calcium
– Total volumetric expansion from magnesium oxide to lansfordite
From air and water
is for example volume 811%.
Mg(OH)2 + CO2  MgCO3.5H2O
Presentation downloadable from www.tececo.com
53
Eco-Cement Strength Gain Curve
HYPOTHETICAL STRENGTH
GAIN CURVE OVER TIME
(Pozzolans added)
MPa
?
OPC Concrete
?
Eco – Cement Concrete with
50% reactive magnesia
?
?
3
Plastic
Stage
7
14
28
Log Days
Eco-cement bricks, blocks, pavers and mortars etc. take a
while to come to the same or greater strength than OPC
formulations but are stronger than lime based formulations.
Presentation downloadable from www.tececo.com
54
Chemistry of Eco-Cements
 There are a number of carbonates of magnesium. The main ones
appear to be an amorphous phase, lansfordite and nesquehonite.
 The carbonation of magnesium hydroxide does not proceed as readily
as that of calcium hydroxide.
– Gor Brucite to nesquehonite = - 38.73 kJ.mol-1
– Compare to Gor Portlandite to calcite = -64.62 kJ.mol-1
 The dehydration of nesquehonite to form magnesite is not favoured by
simple thermodynamics but may occur in the long term under the right
conditions.
 Gor nesquehonite to magnesite = 8.56 kJ.mol-1
– But kinetically driven by desiccation during drying.
 Reactive magnesia can carbonate in dry conditions – so keep bags
sealed!
 For a full discussion of the thermodynamics see our technical
documents.
TecEco technical documents on the web
cover the important aspects of carbonation.
Presentation downloadable from www.tececo.com
55
Eco-Cement Reactions
In Eco - Cements
Magnesia
Amorphous Lansfordite
Brucite
Nesquehonite
MgO + nH2O  Mg(OH)2.nH2O + CO2  MgCO3.nH2O + MgCO3.5H2O + MgCO3.3H2O
Form: Massive-Sometimes Fibrous Often Fibrous Acicular - Needle-like
crystals
Hardness:
2.5 - 3.0
2.5
Solubility (mol.L-1): .00015
.01
.013 (but less in acids)
Compare to the Carbonation of Portlandite
Portlandite
Calcite
Aragonite
Ca(OH)2 + CO2  CaCO3
Form: Massive
Massive or crystalline
Hardness:
Solubility (mol.L-1):
More acicular
2.5
.024
3.5
.00014
Presentation downloadable from www.tececo.com
56
Eco-Cement Micro-Structural Strength
Elongated growths of
lansfordite and
nesquehonite near the
surface, growing inwards
over time and providing
microstructural strength.
Flyash grains (red)
reacting with lime
producing more CSH and
if alkaline enough
conditions bonding
through surface
hydrolysis. Also acting as
micro aggregates.
Portland clinker minerals
(black). Hydration
providing Imperfect
structural framework.
Micro spaces filled with
hydrating magnesia
(→brucite) – acting as a
“waterproof glue”
Mysterious amorphous
phase?
Presentation downloadable from www.tececo.com
57
Carbonation
 Eco-cement is based on blending reactive magnesium oxide with
other hydraulic cements and then allowing the Brucite and
Portlandite components to carbonate in porous materials such as
concretes blocks and mortars.
– Magnesium is a small lightweight atom and the carbonates that form contain
proportionally a lot of CO2 and water and are stronger because of superior
microstructure.
 The use of eco-cements for block manufacture, particularly in
conjunction with the kiln also invented by TecEco (The Tec-Kiln)
would result in sequestration on a massive scale.
 As Fred Pearce reported in New Scientist Magazine (Pearce, F.,
2002), “There is a way to make our city streets as green as the
Amazon rainforest”.
Ancient and modern carbonating lime
mortars are based on this principle
Presentation downloadable from www.tececo.com
58
Aggregate Requirements for Carbonation
 The requirements for totally hydraulic limes and all hydraulic
concretes is to minimise the amount of water for hydraulic
strength and maximise compaction and for this purpose
aggregates that require grading and relatively fine rounded
sands to minimise voids are required
 For carbonating eco-cements and lime mortars on the on the
hand the matrix must “breathe” i.e. they must be porous
– requiring a coarse fraction to cause physical air voids and some vapour
permeability.
 Coarse fractions are required in the aggregates used!
Presentation downloadable from www.tececo.com
59
CO2 Abatement in Eco-Cements
For 85 wt%
Aggregates
15 wt%
Cement
Eco-cements in
porous products
absorb carbon
dioxide from the
atmosphere.
Brucite carbonates
forming lansfordite,
nesquehonite and
an amorphous
phase, completing
the thermodynamic
cycle.
Portland
Cements
15 mass%
Portland
cement, 85
mass%
aggregate
Emissions
.32 tonnes to
the tonne.
After
carbonation.
Approximately
.299 tonne to
the tonne.
No
Capture
11.25% mass%
reactive
magnesia, 3.75
mass% Portland
cement, 85
mass%
aggregate.
Emissions
.37 tonnes to
the tonne. After
carbonation.
approximately
.241 tonne to
the tonne.
Capture
CO2
11.25% mass%
reactive
magnesia, 3.75
mass% Portland
cement, 85
mass%
aggregate.
Emissions
.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 eco-cement, 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.
Presentation downloadable from www.tececo.com
60
TecEco Cement LCA
TecEco
Concretes
will have a
big role post
Kyoto as they
offer potential
sequestration
as well as
waste
utilisation
The TecEco LCA model is
available for download under
“tools” on the web site
Presentation downloadable from www.tececo.com
61
Tec-Cement Reactions
MgO + H2O => Mg(OH)2.nH2O - water consumption
resulting in greater density and higher alkalinity.
Higher alkalinity => more reactions involving silica & alumina.
Mg(OH)2.nH2O => Mg(OH)2 + H2O – slow release water
for more complete hydration of PC
MgO + Al + H2O => 3MgO.Al.6H2O ??? – equivalent to
flash set??
MgO + SO4-- => various Mg oxy sulfates ?? – yes but
more likely ettringite reaction consumes SO 4-- first.
MgO + SiO2 => MSH ?? Yes but high alkalinity required.
Strength??
We think the reactions are relatively
independent of PC reactions
Presentation downloadable from www.tececo.com
62
The Form of MgO Matters
- Lattice Energy Destroys a Myth
 Magnesia, provided it is reactive rather than “dead burned” (or
high density, crystalline periclase type), can be beneficially
added to cements in excess of the amount of 5 mass%
generally considered as the maximum allowable by standards
prevalent in concrete dogma.
– Reactive magnesia is essentially amorphous magnesia with low lattice
energy.
– It is produced at low temperatures and finely ground, and
– will completely hydrate in the same time order as the minerals contained
in most hydraulic cements.
 Dead burned magnesia and lime have high lattice energies
– Crystalline magnesium oxide or periclase has a calculated lattice energy
of 3795 Kj mol-1 which must be overcome for it to go into solution or for
reaction to occur.
– Dead burned magnesia is much less expansive than dead burned lime in
a hydraulic binder (Ramachandran V. S., Concrete Science, Heydon &
Son Ltd. 1981, p 358-360 )
Presentation downloadable from www.tececo.com
63
More Rapid and Greater Strength Development
Higher Strength Binder Ratio
 Concretes are more often than not made to strength.
 The use of tec-cement results in
– 15-30% more strength or less binder for the same strength.
– more rapid early strength development even with added
pozzolans.
Early strength
– Straight line strength development for a long time
gain with less
We have
cement and
HYPOTHETICAL TEC-CEMENT STRENGTH GAIN CURVE
MPa
observed
added
Tec – Cement Concrete with
this sort of
?
10% reactive magnesia
pozzolans is of
curve in over
great
?
500 cubic
?
meters of
economic and
concrete
?
environmental
OPC Concrete
now
importance as
Log Days
28
3
7
14
Plastic Stage
it will allow the
use of more
pozzolans.
Presentation downloadable from www.tececo.com
64
Tec-Cement Strength Development
3
14.365
18.095
19.669
5.516STRENGTH
TEC-CEMENT
COMPRESSIVE
3
9
9
9
21
21
21
35
30
25
16.968
19.466
24.248
29.03
24.54
28.403
32.266
19.44
20.877
24.408
27.939
35.037
36.323
37.609
20.196
13.39
15.39
17.39
25.493
28.723
31.953
WHITTLESEA SLAB
6.656
3.417
4.434
5.451
11.992
13.933
15.874
30
Strength, MPa
STRENGTH ( MPa)
40
20
15
OPC(100%)
10
OPC(90%)+MgO(10%)
5
25
20
Compressive
Strength
15
10
5
0
0
0
0
2
4
6
8
10
12
14
16
18
20
CURING TIME (days)
22
24
5
10
15
20
25
30
Days w ater cured
MPa
Graphs above by Oxford Uni Student are for standard 1PC:3 aggregate mixes, w/c = .5
WHITTLESEA SLAB (A modified
20 mpa mix)
60
40
20
PC = 180 Kg / m3
MgO = 15 Kg / m3
Flyash = 65 Kg / m3
Sam ple 1
Sam ple 2
0
17
30
56
89
Days
Rate of strength development
is of great interest to
engineers and constructors
Presentation downloadable from www.tececo.com
65
Calorimetric Evidence of Faster Strength Gain
Faster Strength
Development
HEAT OF HYDRATION
Evolution of Less
Heat
32
31
30
29
TEMP.( C)
28
27
Energy associated
with complexing?
26
25
24
23
22
21
20
19
18
17
OPC
16
15
OPC+PFA(10%)
0
120
240
360
480
600
720
840
TIME (min)
960 1080 1200 1320 1440
OPC+MgO(10%)
OPC(80%)+PFA(10%)+MgO(10%
)
Presentation downloadable from www.tececo.com
66
Reasons for Compressive Strength Development in Tec-Cements.
 Reactive magnesia requires considerable water to hydrate
resulting in:
– Denser, less permeable concrete. Self compaction?
– 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 of alkalis caused by the removal of water?
 Micro-structural strength due to particle packing (Magnesia
particles at 4-5 micron are a little over ½ the size of cement grains.)
 Formation of MgAl hydrates? Similar to flash set in concrete but
slower??
 Formation of MSH??
 Slow release of water from hydrated Mg(OH)2.nH2O supplying H2O
for more complete hydration of C2S and C3S?
Brucite gains weight in excess of the theoretical increase due to
MgO conversion to Mg(OH)2 in samples cured at 98% RH .
Dr Luc Vandepierre, Cambridge University, 20 September, 2005.
Presentation downloadable from www.tececo.com
67
+
+
+ +
+ Cement + +
MgO
+
+ + +
+
Mutual Repulsion
=>
+
Ph
12 ?
+ + +
Sand +
+
+
+ +
Mutual Repulsion
+ +
+ - +
+
Cement + MgO Sand
+
+
+
- + +
+
+
Mutual Attraction
STRENGTH (MPa)
Greater Tensile Strength
6
5
4
3
OPC(100%)
2
OPC(90%)+ MgO(10%)
1
0
0
2
4
6
8 10 12 14 16 18 20 22 24 26 28 30
CURING TIME (days)
MgO Changes Surface Charge as the Ph Rises.
This could be one of the reasons for the greater tensile
strength displayed during the early plastic phase of teccement concretes. The affect of additives is not yet known
Presentation downloadable from www.tececo.com
68
Durability
 Concretes are said to be less durable when they are physically or
chemically compromised.
 Physical factors can result in chemical reactions reducing
durability
– E.g. Cracking due to shrinkage can allow reactive gases and liquids to
enter the concrete
 Chemical factors can result in physical outcomes reducing
durability
– E.g. Alkali silica reaction opening up cracks allowing other agents such as
sulfate and chloride in seawater to enter.
 This presentation will describe benchmark improvements in
durability as a result of using the new TecEco magnesia cement
technologies
Presentation downloadable from www.tececo.com
69
Crack Collage
Thermal
Freeze Thaw
D Cracks
Alkali aggregate
Reaction
Evaporative
Crazing
Shrinkage
Settlement
Shrinkage
Structural
Plastic
Shrinkage
Corrosion Related
Drying
Shrinkage
Photos from PCA and
US Dept. Ag Websites
Autogenous or self-desiccation shrinkage
(usually related to stoichiometric or chemical shrinkage)
 TecEco technology can reduce if not solve problems of cracking:
–
–
–
–
Related to (shrinkage) through open system loss of water.
As a result of volume change caused by delayed reactions
As a result of corrosion.
Related to autogenous shrinkage
Presentation downloadable from www.tececo.com
70
Causes of Cracking in Concrete
 Cracking commonly occurs when the induced stress exceeds the
maximum tensile stress capacity of concrete and can be caused
by many factors including restraint, extrinsic loads, lack of
support, poor design, volume changes over time, temperature
dependent volume change, corrosion or delayed reactions.
 Causes of induced stresses include:
– Restrained thermal, plastic, drying and stoichiometric shrinkage, corrosion
and delayed reaction strains.
– Slab curling.
– Loading on concrete structures.
 Cracking is undesirable for many reasons
– Visible cracking is unsightly
– Cracking compromises durability because it allows entry of gases and ions
that react with Portlandite.
– Cracking can compromise structural integrity, particularly if it accelerates
corrosion.
Presentation downloadable from www.tececo.com
71
Graphic Illustration of Cracking
Combined Effect of Concrete Volume Change (Example Only)
200
150
Max Tensile Strain
Temperature effect
100
Drying Shrinkage
Autogenous Shrinkage
Total Srain Induced
50
Total Strain Less Creep
0
Tim e since Cast (Hrs)
120
108
96
84
72
60
48
36
24
12
-50
0
Shrinkage/(Expansion) Microstrain
250
Autogenous
shrinkage has
been used to refer
to hydration
shrinkage and is
thus stoichiometric
After Tony Thomas (Boral Ltd.) (Thomas 2005)
Presentation downloadable from www.tececo.com
72
Cracking due to Loss of Water
Brucite gains
weight in excess
of the theoretical
increase due to
MgO conversion
to Mg(OH)2 in
samples cured at
98% RH.
Dr Luc
Vandepierre,
Cambridge
University, 20
September,
2005.
Fool
Drying
Shrinkage
Plastic
Shrinkage
Bucket of Water
Evaporative
Crazing
Shrinkage
Settlement
Shrinkage
Picture from: http://www.pavement.com/techserv/ACI-GlobalWarming.PDF
We may not be able to prevent too much water being added to concrete by fools.
TecEco approach the problem in a different way by providing for the internal
removal/storage of water that can provide for more complete hydration of PC.
Presentation downloadable from www.tececo.com
73
Solving Cracking due to Shrinkage from Loss
of Water
 In the system water plus Portland cement powder plus aggregates
shrinkage is in the order of .05 – 1.5 %.
 Shrinkage causes cracking
 There are two main causes of Portland cements shrinking over
time.
– Stoichiometric (chemical) shrinkage and
– Shrinkage through loss
of water.
 The solution is to:
– Add minerals that compensate by stoichiometrically expanding and/or to
– Use less water, internally hold water or prevent water loss.
 TecEco tec-cements internally hold water and prevent water loss.
MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)
Presentation downloadable from www.tececo.com
74
Preventing Shrinkage through Loss of Water
 When magnesia hydrates it consumes 18 litres of water per mole of
magnesia probably more depending on the value of n in the reaction below:
MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)
 The dimensional change in the system MgO + PC depends on:
–
–
–
The ratio of MgO to PC
Whether water required for hydration of PC and MgO is coming from stoichiometric mix
water (i.e. the amount calculated as required), excess water (bleed or evaporative) or
from outside the system.
In practice tec-cement systems are more closed and thus dimensional change is more a
function of the ratio of MgO to PC
 As a result of preventing the loss of water by closing the system together
with expansive stoichiometry of MgO reactions (see below).
MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)
40.31 + 18.0 ↔ 58.3 molar mass (at least!)
11.2 + liquid ↔ 24.3 molar volumes (at least!)
 It is possible to significantly reduce if not prevent (drying, plastic,
evaporative and some settlement) shrinkage as a result of water losses
from the system.
The molar volume (L.mol-1)is equal to the molar
mass (g.mol-1) divided by the density (g.L-1).
Presentation downloadable from www.tececo.com
75
Preventing Shrinkage through Loss of Water
 Portland cements stoichiometrically require around 23 -27% water
for hydration yet we add approximately 45 to 60% at cement
batching plants to fluidise the mix sufficiently for placement.
 If it were not for the enormous consumption of water by tri calcium
aluminate as it hydrates forming ettringite in the presence of
gypsum, concrete would remain as a weak mush and probably
never set.
– 26 moles of water are consumed per mole of tri calcium aluminate to from a
mole of solid ettringite. When the ettringite later reacts with remaining tri
calcium aluminate to form monosulfoaluminate hydrate a further 4 moles of
water are consumed.
 The addition of reactive MgO achieves water removal internally in
a closed system in a similar way.
MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)
Presentation downloadable from www.tececo.com
76
Other Benefits of Preventing Shrinkage through Loss of
Water
 Internal water consumption also results in:
– Greater strength
• More complete hydration of PC .
• Reduced in situ voids:paste ratio
– Greater density
• Increased durability
• Higher short term alkalinity
• More effective pozzolanic reactions.
 More complete hydration of PC .
– Small substitutions of PC by MgO result in water being trapped
inside concrete as Brucite and Brucite hydrates which can later self
desiccate delivering water to hydration reactions of calcium
silicates (Preventing so called “Autogenous” shrinkage).
Presentation downloadable from www.tececo.com
77
Bleeding is a Bad Thing
 Bleeding is caused by:
– Lack of fines
– Too much water
 Bleeding can be fixed by:
– Reducing water or adding fines
– Air entrainment or grading adjustments
Better to keep
concretes as
closed systems
 Bleeding causes:
–
–
–
–
–
–
–
Reduced pumpability
Loss of cement near the surface of concretes
Delays in finishing
Poor bond between layers of concrete
Interconnected pore structures that allow aggressive agents to enter later
Slump and plastic cracking due to loss of volume from the system
Loss of alkali that should remain in the system for better pozzolanic
reactions
– Loss of pollutants such as heavy metals if wastes are being incorporated.
 Concrete is better as a closed system
Presentation downloadable from www.tececo.com
78
Dimensional Control in Tec-Cement Concretes over
Time
 By adding MgO volume changes are
minimised to close to neutral.
– So far we have observed significantly less shrinkage in
TecEco tec - cement concretes with about (8-10% substitution
OPC) with or without fly ash.
– At some ratio, thought to be around 15-18% reactive
magnesia there is no shrinkage.
– The water lost by concrete as it shrinks is used by the
reactive magnesia as it hydrates eliminating shrinkage.
 Note that brucite is > 44.65 mass% water and
it makes sense to make binders out of water!
 More research is required to accurately
establish volume relationships and causes for
reduced shrinkage.
Presentation downloadable from www.tececo.com
79
Long Term pH control
 TecEco add reactive magnesia which hydrates forming
brucite which is another alkali, but much less soluble,
mobile or reactive than Portlandite.
 Brucite provides long term pH control.
Tec-Cement (red) - more affective
pozzolanic reactions
Surface hydrolysis and more polymeric species?
pH
13.7
11.2
10.5
HYPOTHETICAL pH CURVES
OVER TIME (with fly ash)
?
Tec – Cement Concrete with 10% reactive
?
? magnesia (red). Ph maintained by brucite
OPC Concrete
OPC Concrete – Lower long term pH due
to consumption of lime and carbonation
Log Time
Plastic
Stage
Presentation downloadable from www.tececo.com
A pH in
the
range
10.5 –
11.2 is
ideal in a
concrete
80
Reducing Cracking as a Result of Volume
Change caused by Delayed Reactions
An Alkali Aggregate Reaction Cracked Bridge Element
Photo Courtesy Ahmad Shayan ARRB
Presentation downloadable from www.tececo.com
81
Types of Delayed Reactions
 There are several types of delayed reactions that
cause volume changes (generally expansion) and
cracking.
–
–
–
–
–
Alkali silica reactions
Alkali carbonate reactions
Delayed ettringite formation
Delayed thaumasite formation
Delayed hydration or dead burned lime or periclase.
 Delayed reactions cause dimensional distress,
cracking and possibly even failure.
Presentation downloadable from www.tececo.com
82
Reducing Delayed Reactions
 Delayed reactions do not appear to 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 the reactive magnesia in Tec-cement concretes
consumes unbound water from the pores inside concrete.
– Magnesia dries concrete out from the inside. Reactions do
not occur without water.
Presentation downloadable from www.tececo.com
83
Reduced Steel Corrosion Related Cracking
Rusting Causes Dimensional Distress
 Steel remains protected with a passive oxide coating of
Fe3O4 above pH 8.9.
 A pH of over 8.9 is maintained by the equilibrium
Mg(OH)2 ↔ Mg++ + 2OH- for much longer than the pH
maintained by Ca(OH)2 because:
– Brucite does not react as readily as Portlandite resulting in
reduced carbonation rates and reactions with salts.
 Concrete with brucite in it is denser and carbonation is
expansive, sealing the surface preventing further
access by moisture, CO2 and salts.
Presentation downloadable from www.tececo.com
84
Reduced Steel Corrosion
 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 are 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.)
 As a result of the above the rusting of reinforcement does
not proceed to the same extent.
 Cracking or spalling due to rust does not occur
Presentation downloadable from www.tececo.com
85
Steel Corrosion is Influenced by 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
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.
Steel corrodes below 8.9
Equilibrium pH of Brucite and of lime
Presentation downloadable from www.tececo.com
86
Reducing Cracking Related to Autogenous Shrinkage
 Autogenous shrinkage tends to occur in high
performance concretes in which dense
microstructures develop quickly preventing the entry
of additional water required to complete hydration.
– First defined by Lynam in 1934 (Lynam CG. Growth and movement in
Portland cement concrete. London: Oxford University Press; 1934. p. 26-7.)
 The autogenous deformation of concrete is defined as
the unrestrained, bulk deformation that occurs when
concrete is kept sealed and at a constant temperature.
Presentation downloadable from www.tececo.com
87
Reducing Cracking Related to Autogenous Shrinkage
 Main cause is stoichiometric or chemical shrinkage as
observed by Le Chatelier.
– whereby the reaction products formed during the hydration of
cement occupy less space than the corresponding reactants.
 A dense cement paste hydrating under sealed
conditions will therefore self-desiccate creating empty
pores within developing structure. If external water is
not available to fill these “empty” pores, considerable
shrinkage can result.
Le Chatelier H. Sur les changements de volume qui accompagnent
Ie durcissement des ciments. Bulletin de la Societe
d'Encouragement pour I'Industrie Nationale 1900:54-7.
Presentation downloadable from www.tececo.com
88
Reducing Cracking Related to Autogenous Shrinkage
 Autogenous shrinkage does not occur in high strength tec-cement
concretes because:
– The brucite hydrates that form desiccate back to brucite delivering water in
situ for more complete hydration of Portland cement.
Mg(OH)2.nH2O (s) ↔ MgO (s) + H2O (l)
• As brucite is a relatively weak mineral compressed and densifies the
microstructure.
– The stoichiometric shrinkage of Portland cement (first observed by Le
Chatelier) is compensated for by the stoichiometric expansion of magnesium
oxide on hydration.
MgO (s) + H2O (l) ↔ Mg(OH)2.nH2O (s)
40.31 + 18.0 ↔ 58.3 molar mass (at least!)
11.2 + liquid ↔ 24.3 molar volumes (at least 116% expansion,
probably more initially before desiccation as above!)
Presentation downloadable from www.tececo.com
89
Improved Durability
Materials that last longer need
replacing less often saving on
energy and resources.
 Reasons for Improved Durability:
– Greater Density = Lower Permeability
• Physical Weaknesses => Chemical Attack
– Removal of Portlandite with the Pozzolanic Reaction.
• Removal or reactive components
– Substitution by Brucite => Long Term pH control
• Reducing corrosion
Presentation downloadable from www.tececo.com
90
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
therefore stronger more durable and less
permeable. Cement powder is not lost near the
surfaces. Tec-cements have a higher salt
resistance and less corrosion of steel etc.
Presentation downloadable from www.tececo.com
91
Greater Density – Lower Permeability
 Concretes have a high percentage (around 18% – 22%) of
voids.
 On hydration magnesia expands >=116.9 % filling voids and
surrounding hydrating cement grains => denser concrete.
 On carbonation to nesquehonite brucite expands 307%
sealing the surface.
 Lower voids:paste ratios than water:binder ratios result in
little or no bleed water, lower permeability and greater
density.
Presentation downloadable from www.tececo.com
92
Densification During the Plastic Phase
Observable
Characteristic
Water
Binder +
supplemen
tary
cementitio
us
materials
High water
for ease of
placement
Consumption
of water during
plastic stage
Variables such as %
hydration of mineral,
density, compaction,
% mineral H20 etc.
Log time
Relevant
Fundamental
Voids
Hydrated
Binder
Materials
Unhydrated
Binder
Less water
for strength
and durability
Water is required to
plasticise concrete
for placement,
however once
placed, the less
water over the
amount required for
hydration the better.
Magnesia consumes
water as it hydrates
producing solid
material.
Less water results in increased density and concentration of alkalis less shrinkage and cracking and improved strength and durability.
Presentation downloadable from www.tececo.com
93
Durability - Reduced Salt & Acid 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 it is a least 5
orders of magnitude less soluble, mobile or reactive.
– Ksp brucite = 1.8 X 10-11
– Ksp Portlandite = 5.5 X 10-6
 TecEco cements are more acid resistant than Portland
cement
– This is because of the relatively high acid resistance (?) of
Lansfordite and nesquehonite compared to calcite or aragonite
Presentation downloadable from www.tececo.com
94
Less Freeze - Thaw Problems
 Denser concretes do not let water in.
 Brucite will to a certain extent take up internal stresses
 When magnesia hydrates it expands into the pores left around hydrating
cement grains:
MgO (s) + H2O (l) ↔ Mg(OH)2 (s)
40.31 + 18.0 ↔ 58.3 molar mass
11.2 + 18.0 ↔ 24.3 molar volumes
39.20 ↔ 24.3 molar volumes
At least 38% air voids are created in space that was occupied by magnesia
and water!
 Air entrainment can also be used as in conventional concretes
 TecEco concretes are not attacked by the salts used on roads
Presentation downloadable from www.tececo.com
95
Rosendale Concretes – Proof of Durability



Rosendale cements contained 14 – 30% MgO
A major structure built with Rosendale cements commenced in 1846 was Fort Jefferson near
key west in Florida.
Rosendale cements were recognized for their exceptional durability, even under severe
exposure. At Fort Jefferson much of the 150 year-old Rosendale cement mortar remains in
excellent condition, in spite of the severe ocean exposure and over 100 years of neglect. Fort
Jefferson is nearly a half mile in circumference and has a total lack of expansion joints, yet
shows no signs of cracking or stress. The first phase of a major restoration is currently in
progress.
More information from http://www.rosendalecement.net/rosendale_natural_cement_.html
Presentation downloadable from www.tececo.com
96
Solving Waste & Logistics Problems
 TecEco cementitious composites represent a cost affective option
for
– using non traditional aggregates from on site reducing transports costs and
emissions
– use and immobilisation of waste.
 Because they have
– lower reactivity
• less water
• lower pH
– Reduced solubility of heavy metals
• less mobile salts
– greater durability.
• denser.
• impermeable (tec-cements).
• dimensionally more stable with less shrinkage and cracking.
– homogenous.
– no bleed water.
TecEco Technology - Converting Waste to Resource
Presentation downloadable from www.tececo.com
97
Role of Brucite in Immobilization
 In a Portland cement Brucite matrix
– PC derive CSH takes up lead, some zinc and germanium
– Pozzolanic CSH can take up mobile cations
– Brucite and hydrotalcite are both excellent hosts for toxic and
hazardous wastes.
– Heavy metals not taken up in the structure of Portland cement
minerals or trapped within the brucite layers end up as hydroxides
with minimal solubility.
Layers of
electronically
neutral brucite
suitable for
trapping
balanced
cations and
anions as well
as other
substances.
Van de
waals
bonding
holding the
layers
together.
Salts and
other
substances
trapped
between
the layers.
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.
Presentation downloadable from www.tececo.com
98
Concentration of Dissolved Metal, (mg/L)
Lower Solubility of Metal Hydroxides
There is a 104 difference
10
Pb(OH)
2
Cr(OH) 3
Zn(OH) 2
10 0
Ag(OH)
Cu(OH) 2
Ni(OH) 2
Cd(OH) 2
10 -2
Equilibrium pH of brucite
is 10.52 (more ideal)*
10 -4
10 -6
6
7
8
9
10
Equilibrium pH of PC
CSH is 11.2
11
12
13
*Equilibrium
pH’s in pure
water, no
other ions
present. The
solubility of
toxic metal
hydroxides is
generally less
in the range
pH 10.52 11.2 than at
higher pH’s.
14
Equilibrium pH of
Portlandite is 12.35
All waste streams will contain heavy metals and a
strategy for long term pH control is therefore essential
Presentation downloadable from www.tececo.com
99
Using Wastes and Non-Traditional Aggregates to Make
TecEco Cement Concretes
 Many wastes and local materials can contribute physical
property values.
– Plastics for example are collectively light in weight, have tensile
strength and low conductance.
 Tec, eco and enviro-cements will allow a wide range of
wastes and non-traditional aggregates such as local materials
to be used.
 Tec, enviro and eco-cements are benign binders that are:
– low alkali reducing reaction problems with organic materials.
– stick well to most included wastes
 Tec, enviro and eco-cements can utilize wastes including
carbon to increase sequestration preventing their conversion
to methane
 There are huge volumes of concrete produced annually
(>2 tonnes per person per year)
Presentation downloadable from www.tececo.com
100
Biomimicry - Ultimate Recyclers
 As peak oil looms and the price of transport is
set to rise sharply
– We should not just be recycling based on chemical property
requiring sophisticated equipment and resources
– We should be including wastes based on physical properties
as well as chemical composition in composites whereby they
become local resources.
The Jackdaw recycles all sorts of things it finds nearby based on physical
property.
The bird is not concerned about chemical composition and the nest it
makes could be described as a composite material.
TecEco cements are benign binders
that can incorporate all sort of wastes
without reaction problems. We can
do the same as the Jackdoor
Presentation downloadable from www.tececo.com
101
Using Wastes and Non-Traditional Aggregates to Make
TecEco Cement Concretes
 As the price of fuel rises, the
use of local or on site low
embodied energy materials
rather than carted aggregates
will have to be considered.
No longer an option?
The use of on site and local wastes will be made possible by the use of low reactivity TecEco mixes
and a better understanding of particle packing. We hope with our new software to be able to
demonstrate how adding specific size ranges can make an unusable waste such as a tailing or sludge
suitable for making cementitious materials.
Recent natural disasters such as the recent tsunami and Pakistani earthquake
mean we urgently need to commercialize TecEco technologies because they
provide benign environments allowing the use of many local materials and wastes
without delayed reactions
Presentation downloadable from www.tececo.com
102
Easier to Finish Concretes
Easier to pump and finish
Concretes are likely to have less
water added to them resulting in
less cracking
Presentation downloadable from www.tececo.com
103
Non Newtonian Rheology
It is not
known
how
deep
these +
layers
+
get
Etc.
+
O
+
+
O
-
+
O
O +
O - +
+
+
+
O
- Mg++
O
+
+
Etc.
-
-
O
+
+
+
The strongly
positively charged
small Mg++ atoms
attract water
(which is polar) in
deep layers
introduce a shear
thinning property
affecting the
rheological
properties and
making concretes
less “sticky” with
added pozzolan
Ca++ = 114, Mg++ = 86 picometres
Presentation downloadable from www.tececo.com
104
Bingham Plastic Rheology
Tech Tendons
Second layer low slump teccement concrete
First layer low slump tec-cement
concrete
 TecEco concretes and mortars are:
–
–
–
Very homogenous and do not segregate easily. They exhibit good adhesion and have a
shear thinning property.
Exhibit Bingham plastic qualities and react well to energy input.
Have good workability.
 TecEco concretes with the same water/binder ratio have a lower slump but
greater plasticity and workability.
 TecEco tec-cements are potentially suitable for mortars, renders, patch
cements, colour coatings, pumpable and self compacting concretes.
 A range of pumpable composites with Bingham plastic properties will be
required in the future as buildings will be “printed.”
Presentation downloadable from www.tececo.com
105
Scientific approach to concrete design
 In the past, concrete proportioning was based on experience and
estimates only. TecEco is develloping batching software, using
theory from the world’s best experts theory (F. de Larrard, K. Day),
to optimize mix design and particularly particle packing.
Satterfield, S. G. (2001). Visualization of High
Performance Concrete, National institute of
standard and technology.
Presentation downloadable from www.tececo.com
106
Scientific approach to concrete design (2)
 TecEco sees the optimization of particle as not only a mean to improve the
strength/cost ratio but to improve concrete sustainability. This is because
improving packing (other parameter beiing equal) leads to an increase of:
– The compressive and tensile strength
– The workability
– The durability
And a decrease of:
– The porosity
– The risk of segregation
– The yield stresses (easier to compact)
 Scientific knowledge of the concrete behaviour coupled with the use of
optimization software allows concrete technologist to:
- Design more sustainable concrete
- Use secondary aggregate and mining waste (poor size distribution)
- Dramatically reduce the number of experiment needed to design a
concrete for a special application
Presentation downloadable from www.tececo.com
107
Tec-Cement Concretes
 Tec-Cements contain around 5-20% reactive
MgO and are mainly formulated because of:
–
–
–
–
Superior thixotropic properties
Less cracking and shrinkage
Greater durability
Low reactivity
• Ability to incorporate a wide range of wastes.
TecEco are looking for technical
problems that are not being solved
using conventional formulations as
to us they represent niche markets.
Presentation downloadable from www.tececo.com
108
The TecEco Dream – A More Sustainable Built Environment
CO2
CO2 FOR
GEOLOGICAL
SEQUESTRATION
CO2
MINING
MAGNESITE
+ OTHER
INPUTS
“There is a way to
make our city streets
as green as the
Amazon rainforest”.
Fred Pearce, New
Scientist Magazine
TECECO
KILN
MgO
OTHER
WASTES
PERMANENT
SEQUESTRATION &
WASTE
UTILISATION (Man
made carbonate
rock incorporating
wastes as a
TECECO CONCRETES building material)
RECYCLED
BUILDING
MATERIALS
SUSTAINABLE CITIES
We need materials that
require less energy to
make them, that last
much longer and that
contribute properties
that reduce lifetime
energies
Presentation downloadable from www.tececo.com
109
Sustainable Materials in the Built Environment - 2007
Technical Focus
This Conference will focus on:
 The impacts and connectivity
of different parts of the supply
chain.
 Fabrication, performance,
recycling and waste
 New developments in
materials and processes
 Reviewing existing materials
assessment tools
 Future directions in regulation
 Opportunities/barriers to
introduction of sustainable
materials and technologies in
the building industry.
 New materials and more
sustainable built
environments: the evidence?
Joint Venture Websites
ASSMIC Website: www.aasmic.org
Materials Australia Website: www.materialsaustralia.com.au
Presentation downloadable from www.tececo.com
110