Mr Tharmalingam Maheswaran

1
Mr Tharmalingam Maheswaran
Mr Fred Andrews-Phaedonos
Dr Alan Carse
Mr Greg Yorkston
Mr John Harrison
2
New Cements Based on the Addition of Reactive
Magnesia to Portland Cement With or Without Added
Pozzolan.

• Solving not just mitigating problems

3
Plasticising our Minds

• "The important thing in science is not so much to
  obtain new facts as to discover new ways of
  thinking about them.
• -- Sir William Bragg
• "Imagination has brought mankind through the dark
  agesto its present state of civilization.Imagina
  tion led Columbus to discover America.Imagination
  led Franklin to discover electricity.Imagination
  has given us the steam engine,the telephone the
  talking-machine, and the automobile,for these
  things had to be dreamed of before they became
  realities.
• -- L. Frank Baum
• Imagination is more important than knowledge,
  knowledge is limited.
• -- Albert Einstein

4
Problems Remaining with Portland Type Cements

• Problems talked about
• Short time for placing and finishing
• Shrinkage
• Cracking, crack control
• Durability and Performance
• Sulphate and chloride resistance
• Carbonation
• Corrosion of steel and other reinforcing
• Abrasion resistance of pavement
• Major problem not discussed
• Sustainability
• Emissions and embodied energies

Under 1/3 of the papers presented at Concrete in
the Third Millennium Conference Brisbane July
2003
Maybe the discussion should be more about how we
may be able to overcome - not just mitigate these
problems.
5
Potential for Change

• Globally some 2 billion tonnes of cement, lime
  and magnesia are produced annually.
• Consuming large amounts of energy
• Around 98 of the worlds energy is derived from
  fossil fuels that when burnt to produce energy
  they release vast amounts of CO2
• The production of Portland cement clinker, lime
  and magnesia all consume energy.
• The production of Portland cement, lime and
  reactive magnesia also result in the release of
  chemically bound CO2.
• Responsible between 5 and 10 of global
  emissions
• The built environment is our footprint on earth.
  Buildings account for 30 of the raw materials
  used, 42 of the energy, 25 of water, 12 of
  land use, 40 of atmospheric emissions, 20 of
  water effluents, 25 of solid waste and 13 of
  other releases. Include infrastructure and the
  numbers are more.
• There is a huge potential to change Portland
  cement to improve sustainability and properties.
• These days technology improvements fuel economic
  growth.

6
Imagine the consequences of getting rid of the
lime and filling all these voids as Portland
cement hydrates with an almost insoluble sticky
alkaline paste.
Partially hydrated Portland cement paste
Soroos,1999 .
7
TecEco Cements
John Harrison B.Sc. B.Ec. FCPA.
8
TecEco Cement Summary

• TecEco cements are a system of blending reactive
  magnesia, Portland cement and usually a pozzolan.
• Two main formulation groups.
• TecEco modified Portland cements.
• Contain more Portland cement than reactive
  magnesia
• The role of magnesia as it hydrates is to densify
  and protect.
• Other benefits include improvements in rheology
• TecEco eco-cements
• Contain more reactive magnesia than Portland
  cement.
• The brucite formed eventually carbonates
• Forming stronger fibrous minerals.
• Resulting in huge opportunities for abatement.

9
Basic Chemical Reactions
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Understanding TecEco Modified Portland Cements

• The easiest way to understand TecEco modified
  Portland cements is to think of the ramifications
  of replacing lime in Portland cement with brucite
  (Mg(OH)2).
• TecEco achieve this by removing the lime with a
  pozzolan and replacing it with reactive magnesia
  that hydrates filling in the voids.
• The mean size of the reactive magnesia TecEco
  have been using is less than 10 micron, compared
  to Portland cement at around 80 micron
• Highly reactive magnesia and usually a pozzolan
  are required to prevent dimensional distress.

11
Understanding TecEco Eco-Cements

• The easiest way to understand eco-cements work is
  to think of a lime Portland mortar such as a
  116-9 formulation. Replace the lime with
  reactive magnesia and reduce the proportion of
  Portland cement by around half. Add fly ash to
  consume the lime produced as Portland cement
  hydrates. The reactive magnesia will first
  hydrate and then carbonate as would have the lime
  in porous materials.
• Dimensional distress is not potentially so much
  of a problem in porous materials such as bricks,
  blocks, pavers and mortars and possibly even
  roads and footpath pavement (which should be
  porous.)

12
Overcoming Delayed Hydration.

• Delayed hydration leads to dimensional distress.
• Magnesium was banned in Portland cements because
  when it goes through the high temperature process
  of making Portland cement it becomes dead burned.
• Dead burned lime is much more expansive than dead
  burned magnesia1.
• Reactivity of magnesia is a function of state of
  disorder, specific surface area and glass forming
  impurities. Make a particle small enough and it
  will react with just about anything! 2
• 1 Ramachandran V. S., Concrete Science, Heydon
  Son Ltd. 1981, p 358-360.
• 2 Dr Bob Solomon a former geology lecturer of
  mine at the University of Tasmania

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Ramifications of Adding Reactive Magnesia

• Durability TecEco cements include highly
  insoluble minerals that last indefinitely. They
  will potentially maintain pH at ideal levels,
  protect steel reinforcing and reduce alkali
  aggregate reactions.
• Lower Materials Cost With economies of scale
  TecEco cements could reduce costs.
• Easy to Use With improved homogeneity and
  rheology. Fine magnesia acts as a lubricant for
  Portland cement and takes up bleed water as it
  hydrates.
• Greater Strength? Less shrinkage? A lower water
  cement ratio could mean greater strength and less
  shrinkage. Still to be examined but so far so
  good!
• Insulating Properties / High Thermal Mass / Low
  Embodied Energy Eco-cement products will be
  favoured for energy conserving buildings.
• Waste Materials TecEco cements and Eco-cements
  use a high proportion of recycled materials.
• Recyclable Eco-cement products can be
  reprocessed and reused, making them more
  attractive to many users.
• A Fire Retardant Eco-cement products put fires
  out by releasing CO2
• Low Capital Cost No new plant and equipment is
  required.
• Environmentally Friendly!

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Durability of TecEco Cement Concretes

• Reducing Corrosion.
• Portlandite is removed in reactions with
  Pozzolans.
• Replacement of Portlandite which carbonates
  readily and being soluble can act as an
  electrolyte by brucite which is much less
  soluble, does not act as an electrolyte or
  carbonate as readily.
• Portlandite - Free Energy of Formation of
  Carbonate ?Gor - 64.62 kJ.mol-1, Ksp 5.5 X
  10-6
• Brucite - Free Energy of Formation of Carbonate
  ?Gor - 19.55 kJ.mol-1, Ksp 1.8 X 10-11
• Lower More Stable pH for much Longer?
• As Portlandite is removed the pH becomes governed
  by the solubility of brucite and is much lower at
  around 10.5 -11 reducing problems such as AAR and
  etching, but still high enough to keep Fe and
  Fe3O4 stable (See Pourbaix diagram)
• Increased Density
• As reactive magnesia is much finer than Portland
  cement it tends to act as a lubricant improving
  rheology even without plasticiser and lowering
  the water cement ratio.
• Brucite also densifies the matrix by filling in
  pore spaces taking up mix and bleed water as it
  hydrates.

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Eh-pH or Pourbaix Diagram
The stability fields of iron in the presence of
oxygen and carbon dioxide. Source Krauskopf K.
B., Introduction to Geochemistry, McGraw Hill
Book Company, 1967, page 168, after Garrels
Christ (1965), page 224.
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TecEco Modified Portland Cements

• Improving the triple bottom line (society, the
  economy and the environment )
• Durability and corrosion may become problemsof
  the past.
• Lower use of materials and energyover time
  saving money and the environment.
• Concretes may become easier to use with less
  problems.
• AAR, shrinkage, steel corrosion, fire resistance,
  placement and finish time are all problems that
  may be solved to varying extents.
• Lower Costs
• Making reactive magnesia is a benign process with
  potential for using waste energy.
• A wider range of aggregates including wastes will
  be availablereducing cartage costs and
  emissions.
• Higher Standard of Living
• More with less cost to the environment.

17
TecEco Eco - Cements for Sustainable Cities
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TecEco Eco-Cements - Solving Waste Problems

• The best thing to do with wastes isif at all
  possible to use them. If theycannot directly be
  used then they haveto be immobilised
• TecEco eco-cements are ideal for
  utilisinghazardous wastes such as fly and bottom
  ash,iron slags, red mud etc.
• TecEco Modified Portland cements are excellent
  for toxic and hazardous waste immobilisation as
  they are not corrodedby ground or sea water.
• TecEco Cements are a formidable solution to toxic
  and hazardous waste fixation problems

19
The Magnesium Thermodynamic Cycle
20
Manufacture of Portland Cement
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Abatement of Emissions

• The production of Portland cement clinker, lime
  and magnesia all consume energy
• Around 98 of the worlds energy is derived from
  fossil fuels that when burnt to produce energy
  release vast amounts of CO2
• The production of Portland cement, lime and
  reactive magnesia also results in the release of
  chemically bound CO2
• Some of TecEcos early publications on emissions
  were not very clear as to how they were abated
  and this has been compounded by the press. How
  CO2 releases are abated in TecEco modified
  Portland cements and eco-cements is discussed in
  detail in newsletter 28 freely available on the
  web.

22
Emissions
23
Abatement TecEco Eco-Cements
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Global Abatement
25
Substitution (Millions of Tonnes)
Concretes already have low lifetime energies. If
embodied energies are improved could
substitution mean greater market share?
Figures are in millons of Tonnes
26
TecEco Kiln Technology

• Calcining and grinding occur at the same time.
• Clastic conditions lower the state of disorder.
  Heat is literally squashed into a material.
• CO2 can be captured at source.
• The heat lost through grinding is used for
  calcining.
• Approx 25 greater efficiency.
• Much more reactive magnesia should result.

27
TecEcos Immediate Focus

• Raise money for Research Around 4 millions
  dollars worth in the pipeline.
• Focus is on defined markets for low technical
  risk products that require minimal research and
  development and for which performance based
  standards apply.
• Carbonated products such as bricks, blocks,
  stabilised earth blocks, pavers, roof tiles and
  mortars for the masonry industry that utilise
  large quantities of waste and products where
  sustainability, rheology or fire retardation are
  an issue. (Mainly eco-cement technology using fly
  ash).
• The immobilisation of wastes including toxic
  hazardous and other wastes because of the
  superior performance of the technology and the
  rapid growth of markets. (Eco-cements and
  modified Portland cements).
• Products where extreme durability is required.
• Products for which weight is an issue.
• Considerable interest is also being shown in the
  new TecEco kiln design and the Tech Tendon method
  of prestressing, partial prestressing and
  reinforcing.

28
TecEco Minding the Future

• TecEco are aware of the enormous weight
  ofopinion necessary before standards can
  bechanged globally for TecEco modified
  cementconcretes for general use.
• TecEco already have a number of students at
  universities around the world doing research
• TecEco have publicly released the technology.
• TecEco research documents are available from
  TecEco by request. Soon they will be able to be
  purchased from the web site.
• Other documents by other researchers will be made
  available in a similar manner as they become
  available.
• TecEco have received huge global publicity not
  all of which is correct!

Technology standing on its own is not inherently
good. It still matters whether it is operating
from the right value system and whether it is
properly available to all people. -- William
Jefferson Clinton
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Manufacture of Eco-Cement Products
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TecEco Technology Summary

• Simple, Smart and Sustainable
• TecEco cement technology has resulted in
  potential solutions to the problem of the rusting
  of steel in concrete, the alkali aggregate
  reaction problem and the immobilisation of many
  problem wastes and will provides a range of more
  sustainable building materials.
• The Right Technology at the Right Time?
• TecEco cement technology addresses important
  triple bottom line issues solving major global
  problems with positive economic and social
  outcomes.