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Mr Tharmalingam Maheswaran

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Title: 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
10
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

13
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!

14
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.

15
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.
16
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
18
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
21
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
24
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
29
Manufacture of Eco-Cement Products
30
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.
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